<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<!--[if IE]><meta http-equiv="X-UA-Compatible" content="IE=edge"><![endif]-->
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="generator" content="Asciidoctor 1.5.8">
<title>imageReadFunctions(3)</title>
<style>
/*! normalize.css v2.1.2 | MIT License | git.io/normalize */
/* ========================================================================== HTML5 display definitions ========================================================================== */
/** Correct `block` display not defined in IE 8/9. */
article, aside, details, figcaption, figure, footer, header, hgroup, main, nav, section, summary { display: block; }

/** Correct `inline-block` display not defined in IE 8/9. */
audio, canvas, video { display: inline-block; }

/** Prevent modern browsers from displaying `audio` without controls. Remove excess height in iOS 5 devices. */
audio:not([controls]) { display: none; height: 0; }

/** Address `[hidden]` styling not present in IE 8/9. Hide the `template` element in IE, Safari, and Firefox < 22. */
[hidden], template { display: none; }

script { display: none !important; }

/* ========================================================================== Base ========================================================================== */
/** 1. Set default font family to sans-serif. 2. Prevent iOS text size adjust after orientation change, without disabling user zoom. */
html { font-family: sans-serif; /* 1 */ -ms-text-size-adjust: 100%; /* 2 */ -webkit-text-size-adjust: 100%; /* 2 */ }

/** Remove default margin. */
body { margin: 0; }

/* ========================================================================== Links ========================================================================== */
/** Remove the gray background color from active links in IE 10. */
a { background: transparent; }

/** Address `outline` inconsistency between Chrome and other browsers. */
a:focus { outline: thin dotted; }

/** Improve readability when focused and also mouse hovered in all browsers. */
a:active, a:hover { outline: 0; }

/* ========================================================================== Typography ========================================================================== */
/** Address variable `h1` font-size and margin within `section` and `article` contexts in Firefox 4+, Safari 5, and Chrome. */
h1 { font-size: 2em; margin: 0.67em 0; }

/** Address styling not present in IE 8/9, Safari 5, and Chrome. */
abbr[title] { border-bottom: 1px dotted; }

/** Address style set to `bolder` in Firefox 4+, Safari 5, and Chrome. */
b, strong { font-weight: bold; }

/** Address styling not present in Safari 5 and Chrome. */
dfn { font-style: italic; }

/** Address differences between Firefox and other browsers. */
hr { -moz-box-sizing: content-box; box-sizing: content-box; height: 0; }

/** Address styling not present in IE 8/9. */
mark { background: #ff0; color: #000; }

/** Correct font family set oddly in Safari 5 and Chrome. */
code, kbd, pre, samp { font-family: monospace, serif; font-size: 1em; }

/** Improve readability of pre-formatted text in all browsers. */
pre { white-space: pre-wrap; }

/** Set consistent quote types. */
q { quotes: "\201C" "\201D" "\2018" "\2019"; }

/** Address inconsistent and variable font size in all browsers. */
small { font-size: 80%; }

/** Prevent `sub` and `sup` affecting `line-height` in all browsers. */
sub, sup { font-size: 75%; line-height: 0; position: relative; vertical-align: baseline; }

sup { top: -0.5em; }

sub { bottom: -0.25em; }

/* ========================================================================== Embedded content ========================================================================== */
/** Remove border when inside `a` element in IE 8/9. */
img { border: 0; }

/** Correct overflow displayed oddly in IE 9. */
svg:not(:root) { overflow: hidden; }

/* ========================================================================== Figures ========================================================================== */
/** Address margin not present in IE 8/9 and Safari 5. */
figure { margin: 0; }

/* ========================================================================== Forms ========================================================================== */
/** Define consistent border, margin, and padding. */
fieldset { border: 1px solid #c0c0c0; margin: 0 2px; padding: 0.35em 0.625em 0.75em; }

/** 1. Correct `color` not being inherited in IE 8/9. 2. Remove padding so people aren't caught out if they zero out fieldsets. */
legend { border: 0; /* 1 */ padding: 0; /* 2 */ }

/** 1. Correct font family not being inherited in all browsers. 2. Correct font size not being inherited in all browsers. 3. Address margins set differently in Firefox 4+, Safari 5, and Chrome. */
button, input, select, textarea { font-family: inherit; /* 1 */ font-size: 100%; /* 2 */ margin: 0; /* 3 */ }

/** Address Firefox 4+ setting `line-height` on `input` using `!important` in the UA stylesheet. */
button, input { line-height: normal; }

/** Address inconsistent `text-transform` inheritance for `button` and `select`. All other form control elements do not inherit `text-transform` values. Correct `button` style inheritance in Chrome, Safari 5+, and IE 8+. Correct `select` style inheritance in Firefox 4+ and Opera. */
button, select { text-transform: none; }

/** 1. Avoid the WebKit bug in Android 4.0.* where (2) destroys native `audio` and `video` controls. 2. Correct inability to style clickable `input` types in iOS. 3. Improve usability and consistency of cursor style between image-type `input` and others. */
button, html input[type="button"], input[type="reset"], input[type="submit"] { -webkit-appearance: button; /* 2 */ cursor: pointer; /* 3 */ }

/** Re-set default cursor for disabled elements. */
button[disabled], html input[disabled] { cursor: default; }

/** 1. Address box sizing set to `content-box` in IE 8/9. 2. Remove excess padding in IE 8/9. */
input[type="checkbox"], input[type="radio"] { box-sizing: border-box; /* 1 */ padding: 0; /* 2 */ }

/** 1. Address `appearance` set to `searchfield` in Safari 5 and Chrome. 2. Address `box-sizing` set to `border-box` in Safari 5 and Chrome (include `-moz` to future-proof). */
input[type="search"] { -webkit-appearance: textfield; /* 1 */ -moz-box-sizing: content-box; -webkit-box-sizing: content-box; /* 2 */ box-sizing: content-box; }

/** Remove inner padding and search cancel button in Safari 5 and Chrome on OS X. */
input[type="search"]::-webkit-search-cancel-button, input[type="search"]::-webkit-search-decoration { -webkit-appearance: none; }

/** Remove inner padding and border in Firefox 4+. */
button::-moz-focus-inner, input::-moz-focus-inner { border: 0; padding: 0; }

/** 1. Remove default vertical scrollbar in IE 8/9. 2. Improve readability and alignment in all browsers. */
textarea { overflow: auto; /* 1 */ vertical-align: top; /* 2 */ }

/* ========================================================================== Tables ========================================================================== */
/** Remove most spacing between table cells. */
table { border-collapse: collapse; border-spacing: 0; }

meta.foundation-mq-small { font-family: "only screen and (min-width: 768px)"; width: 768px; }

meta.foundation-mq-medium { font-family: "only screen and (min-width:1280px)"; width: 1280px; }

meta.foundation-mq-large { font-family: "only screen and (min-width:1440px)"; width: 1440px; }

*, *:before, *:after { -moz-box-sizing: border-box; -webkit-box-sizing: border-box; box-sizing: border-box; }

html, body { font-size: 100%; }

body { background: white; color: #222222; padding: 0; margin: 0; font-family: "Helvetica Neue", "Helvetica", Helvetica, Arial, sans-serif; font-weight: normal; font-style: normal; line-height: 1; position: relative; cursor: auto; }

a:hover { cursor: pointer; }

img, object, embed { max-width: 100%; height: auto; }

object, embed { height: 100%; }

img { -ms-interpolation-mode: bicubic; }

#map_canvas img, #map_canvas embed, #map_canvas object, .map_canvas img, .map_canvas embed, .map_canvas object { max-width: none !important; }

.left { float: left !important; }

.right { float: right !important; }

.text-left { text-align: left !important; }

.text-right { text-align: right !important; }

.text-center { text-align: center !important; }

.text-justify { text-align: justify !important; }

.hide { display: none; }

.antialiased { -webkit-font-smoothing: antialiased; }

img { display: inline-block; vertical-align: middle; }

textarea { height: auto; min-height: 50px; }

select { width: 100%; }

object, svg { display: inline-block; vertical-align: middle; }

.center { margin-left: auto; margin-right: auto; }

.spread { width: 100%; }

p.lead, .paragraph.lead > p, #preamble > .sectionbody > .paragraph:first-of-type p { font-size: 1.21875em; line-height: 1.6; }

.subheader, .admonitionblock td.content > .title, .audioblock > .title, .exampleblock > .title, .imageblock > .title, .listingblock > .title, .literalblock > .title, .stemblock > .title, .openblock > .title, .paragraph > .title, .quoteblock > .title, table.tableblock > .title, .verseblock > .title, .videoblock > .title, .dlist > .title, .olist > .title, .ulist > .title, .qlist > .title, .hdlist > .title { line-height: 1.4; color: black; font-weight: 300; margin-top: 0.2em; margin-bottom: 0.5em; }

/* Typography resets */
div, dl, dt, dd, ul, ol, li, h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6, pre, form, p, blockquote, th, td { margin: 0; padding: 0; direction: ltr; }

/* Default Link Styles */
a { color: #0068b0; text-decoration: none; line-height: inherit; }
a:hover, a:focus { color: #333333; }
a img { border: none; }

/* Default paragraph styles */
p { font-family: Noto, sans-serif; font-weight: normal; font-size: 1em; line-height: 1.6; margin-bottom: 0.75em; text-rendering: optimizeLegibility; }
p aside { font-size: 0.875em; line-height: 1.35; font-style: italic; }

/* Default header styles */
h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { font-family: Noto, sans-serif; font-weight: normal; font-style: normal; color: black; text-rendering: optimizeLegibility; margin-top: 0.5em; margin-bottom: 0.5em; line-height: 1.2125em; }
h1 small, h2 small, h3 small, #toctitle small, .sidebarblock > .content > .title small, h4 small, h5 small, h6 small { font-size: 60%; color: #4d4d4d; line-height: 0; }

h1 { font-size: 2.125em; }

h2 { font-size: 1.6875em; }

h3, #toctitle, .sidebarblock > .content > .title { font-size: 1.375em; }

h4 { font-size: 1.125em; }

h5 { font-size: 1.125em; }

h6 { font-size: 1em; }

hr { border: solid #dddddd; border-width: 1px 0 0; clear: both; margin: 1.25em 0 1.1875em; height: 0; }

/* Helpful Typography Defaults */
em, i { font-style: italic; line-height: inherit; }

strong, b { font-weight: bold; line-height: inherit; }

small { font-size: 60%; line-height: inherit; }

code { font-family: Consolas, "Liberation Mono", Courier, monospace; font-weight: normal; color: #264357; }

/* Lists */
ul, ol, dl { font-size: 1em; line-height: 1.6; margin-bottom: 0.75em; list-style-position: outside; font-family: Noto, sans-serif; }

ul, ol { margin-left: 1.5em; }
ul.no-bullet, ol.no-bullet { margin-left: 1.5em; }

/* Unordered Lists */
ul li ul, ul li ol { margin-left: 1.25em; margin-bottom: 0; font-size: 1em; /* Override nested font-size change */ }
ul.square li ul, ul.circle li ul, ul.disc li ul { list-style: inherit; }
ul.square { list-style-type: square; }
ul.circle { list-style-type: circle; }
ul.disc { list-style-type: disc; }
ul.no-bullet { list-style: none; }

/* Ordered Lists */
ol li ul, ol li ol { margin-left: 1.25em; margin-bottom: 0; }

/* Definition Lists */
dl dt { margin-bottom: 0.3em; font-weight: bold; }
dl dd { margin-bottom: 0.75em; }

/* Abbreviations */
abbr, acronym { text-transform: uppercase; font-size: 90%; color: black; border-bottom: 1px dotted #dddddd; cursor: help; }

abbr { text-transform: none; }

/* Blockquotes */
blockquote { margin: 0 0 0.75em; padding: 0.5625em 1.25em 0 1.1875em; border-left: 1px solid #dddddd; }
blockquote cite { display: block; font-size: 0.8125em; color: #5e93b8; }
blockquote cite:before { content: "\2014 \0020"; }
blockquote cite a, blockquote cite a:visited { color: #5e93b8; }

blockquote, blockquote p { line-height: 1.6; color: #333333; }

/* Microformats */
.vcard { display: inline-block; margin: 0 0 1.25em 0; border: 1px solid #dddddd; padding: 0.625em 0.75em; }
.vcard li { margin: 0; display: block; }
.vcard .fn { font-weight: bold; font-size: 0.9375em; }

.vevent .summary { font-weight: bold; }
.vevent abbr { cursor: auto; text-decoration: none; font-weight: bold; border: none; padding: 0 0.0625em; }

@media only screen and (min-width: 768px) { h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { line-height: 1.4; }
  h1 { font-size: 2.75em; }
  h2 { font-size: 2.3125em; }
  h3, #toctitle, .sidebarblock > .content > .title { font-size: 1.6875em; }
  h4 { font-size: 1.4375em; } }
/* Tables */
table { background: white; margin-bottom: 1.25em; border: solid 1px #d8d8ce; }
table thead, table tfoot { background: -webkit-linear-gradient(top, #add386, #90b66a); font-weight: bold; }
table thead tr th, table thead tr td, table tfoot tr th, table tfoot tr td { padding: 0.5em 0.625em 0.625em; font-size: inherit; color: white; text-align: left; }
table tr th, table tr td { padding: 0.5625em 0.625em; font-size: inherit; color: #6d6e71; }
table tr.even, table tr.alt, table tr:nth-of-type(even) { background: #edf2f2; }
table thead tr th, table tfoot tr th, table tbody tr td, table tr td, table tfoot tr td { display: table-cell; line-height: 1.4; }

body { -moz-osx-font-smoothing: grayscale; -webkit-font-smoothing: antialiased; tab-size: 4; }

h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { line-height: 1.4; }

a:hover, a:focus { text-decoration: underline; }

.clearfix:before, .clearfix:after, .float-group:before, .float-group:after { content: " "; display: table; }
.clearfix:after, .float-group:after { clear: both; }

*:not(pre) > code { font-size: inherit; font-style: normal !important; letter-spacing: 0; padding: 0; background-color: white; -webkit-border-radius: 0; border-radius: 0; line-height: inherit; word-wrap: break-word; }
*:not(pre) > code.nobreak { word-wrap: normal; }
*:not(pre) > code.nowrap { white-space: nowrap; }

pre, pre > code { line-height: 1.6; color: #264357; font-family: Consolas, "Liberation Mono", Courier, monospace; font-weight: normal; }

em em { font-style: normal; }

strong strong { font-weight: normal; }

.keyseq { color: #333333; }

kbd { font-family: Consolas, "Liberation Mono", Courier, monospace; display: inline-block; color: black; font-size: 0.65em; line-height: 1.45; background-color: #f7f7f7; border: 1px solid #ccc; -webkit-border-radius: 3px; border-radius: 3px; -webkit-box-shadow: 0 1px 0 rgba(0, 0, 0, 0.2), 0 0 0 0.1em white inset; box-shadow: 0 1px 0 rgba(0, 0, 0, 0.2), 0 0 0 0.1em white inset; margin: 0 0.15em; padding: 0.2em 0.5em; vertical-align: middle; position: relative; top: -0.1em; white-space: nowrap; }

.keyseq kbd:first-child { margin-left: 0; }

.keyseq kbd:last-child { margin-right: 0; }

.menuseq, .menuref { color: #000; }

.menuseq b:not(.caret), .menuref { font-weight: inherit; }

.menuseq { word-spacing: -0.02em; }
.menuseq b.caret { font-size: 1.25em; line-height: 0.8; }
.menuseq i.caret { font-weight: bold; text-align: center; width: 0.45em; }

b.button:before, b.button:after { position: relative; top: -1px; font-weight: normal; }

b.button:before { content: "["; padding: 0 3px 0 2px; }

b.button:after { content: "]"; padding: 0 2px 0 3px; }

#header, #content, #footnotes, #footer { width: 100%; margin-left: auto; margin-right: auto; margin-top: 0; margin-bottom: 0; max-width: 62.5em; *zoom: 1; position: relative; padding-left: 1.5em; padding-right: 1.5em; }
#header:before, #header:after, #content:before, #content:after, #footnotes:before, #footnotes:after, #footer:before, #footer:after { content: " "; display: table; }
#header:after, #content:after, #footnotes:after, #footer:after { clear: both; }

#content { margin-top: 1.25em; }

#content:before { content: none; }

#header > h1:first-child { color: black; margin-top: 2.25rem; margin-bottom: 0; }
#header > h1:first-child + #toc { margin-top: 8px; border-top: 1px solid #dddddd; }
#header > h1:only-child, body.toc2 #header > h1:nth-last-child(2) { border-bottom: 1px solid #dddddd; padding-bottom: 8px; }
#header .details { border-bottom: 1px solid #dddddd; line-height: 1.45; padding-top: 0.25em; padding-bottom: 0.25em; padding-left: 0.25em; color: #5e93b8; display: -ms-flexbox; display: -webkit-flex; display: flex; -ms-flex-flow: row wrap; -webkit-flex-flow: row wrap; flex-flow: row wrap; }
#header .details span:first-child { margin-left: -0.125em; }
#header .details span.email a { color: #333333; }
#header .details br { display: none; }
#header .details br + span:before { content: "\00a0\2013\00a0"; }
#header .details br + span.author:before { content: "\00a0\22c5\00a0"; color: #333333; }
#header .details br + span#revremark:before { content: "\00a0|\00a0"; }
#header #revnumber { text-transform: capitalize; }
#header #revnumber:after { content: "\00a0"; }

#content > h1:first-child:not([class]) { color: black; border-bottom: 1px solid #dddddd; padding-bottom: 8px; margin-top: 0; padding-top: 1rem; margin-bottom: 1.25rem; }

#toc { border-bottom: 0 solid #dddddd; padding-bottom: 0.5em; }
#toc > ul { margin-left: 0.125em; }
#toc ul.sectlevel0 > li > a { font-style: italic; }
#toc ul.sectlevel0 ul.sectlevel1 { margin: 0.5em 0; }
#toc ul { font-family: Noto, sans-serif; list-style-type: none; }
#toc li { line-height: 1.3334; margin-top: 0.3334em; }
#toc a { text-decoration: none; }
#toc a:active { text-decoration: underline; }

#toctitle { color: black; font-size: 1.2em; }

@media only screen and (min-width: 768px) { #toctitle { font-size: 1.375em; }
  body.toc2 { padding-left: 15em; padding-right: 0; }
  #toc.toc2 { margin-top: 0 !important; background-color: white; position: fixed; width: 15em; left: 0; top: 0; border-right: 1px solid #dddddd; border-top-width: 0 !important; border-bottom-width: 0 !important; z-index: 1000; padding: 1.25em 1em; height: 100%; overflow: auto; }
  #toc.toc2 #toctitle { margin-top: 0; margin-bottom: 0.8rem; font-size: 1.2em; }
  #toc.toc2 > ul { font-size: 0.9em; margin-bottom: 0; }
  #toc.toc2 ul ul { margin-left: 0; padding-left: 1em; }
  #toc.toc2 ul.sectlevel0 ul.sectlevel1 { padding-left: 0; margin-top: 0.5em; margin-bottom: 0.5em; }
  body.toc2.toc-right { padding-left: 0; padding-right: 15em; }
  body.toc2.toc-right #toc.toc2 { border-right-width: 0; border-left: 1px solid #dddddd; left: auto; right: 0; } }
@media only screen and (min-width: 1280px) { body.toc2 { padding-left: 20em; padding-right: 0; }
  #toc.toc2 { width: 20em; }
  #toc.toc2 #toctitle { font-size: 1.375em; }
  #toc.toc2 > ul { font-size: 0.95em; }
  #toc.toc2 ul ul { padding-left: 1.25em; }
  body.toc2.toc-right { padding-left: 0; padding-right: 20em; } }
#content #toc { border-style: solid; border-width: 1px; border-color: #e6e6e6; margin-bottom: 1.25em; padding: 1.25em; background: white; -webkit-border-radius: 0; border-radius: 0; }
#content #toc > :first-child { margin-top: 0; }
#content #toc > :last-child { margin-bottom: 0; }

#footer { max-width: 100%; background-color: none; padding: 1.25em; }

#footer-text { color: black; line-height: 1.44; }

#content { margin-bottom: 0.625em; }

.sect1 { padding-bottom: 0.625em; }

@media only screen and (min-width: 768px) { #content { margin-bottom: 1.25em; }
  .sect1 { padding-bottom: 1.25em; } }
.sect1:last-child { padding-bottom: 0; }

.sect1 + .sect1 { border-top: 0 solid #dddddd; }

#content h1 > a.anchor, h2 > a.anchor, h3 > a.anchor, #toctitle > a.anchor, .sidebarblock > .content > .title > a.anchor, h4 > a.anchor, h5 > a.anchor, h6 > a.anchor { position: absolute; z-index: 1001; width: 1.5ex; margin-left: -1.5ex; display: block; text-decoration: none !important; visibility: hidden; text-align: center; font-weight: normal; }
#content h1 > a.anchor:before, h2 > a.anchor:before, h3 > a.anchor:before, #toctitle > a.anchor:before, .sidebarblock > .content > .title > a.anchor:before, h4 > a.anchor:before, h5 > a.anchor:before, h6 > a.anchor:before { content: "\00A7"; font-size: 0.85em; display: block; padding-top: 0.1em; }
#content h1:hover > a.anchor, #content h1 > a.anchor:hover, h2:hover > a.anchor, h2 > a.anchor:hover, h3:hover > a.anchor, #toctitle:hover > a.anchor, .sidebarblock > .content > .title:hover > a.anchor, h3 > a.anchor:hover, #toctitle > a.anchor:hover, .sidebarblock > .content > .title > a.anchor:hover, h4:hover > a.anchor, h4 > a.anchor:hover, h5:hover > a.anchor, h5 > a.anchor:hover, h6:hover > a.anchor, h6 > a.anchor:hover { visibility: visible; }
#content h1 > a.link, h2 > a.link, h3 > a.link, #toctitle > a.link, .sidebarblock > .content > .title > a.link, h4 > a.link, h5 > a.link, h6 > a.link { color: black; text-decoration: none; }
#content h1 > a.link:hover, h2 > a.link:hover, h3 > a.link:hover, #toctitle > a.link:hover, .sidebarblock > .content > .title > a.link:hover, h4 > a.link:hover, h5 > a.link:hover, h6 > a.link:hover { color: black; }

.audioblock, .imageblock, .literalblock, .listingblock, .stemblock, .videoblock { margin-bottom: 1.25em; }

.admonitionblock td.content > .title, .audioblock > .title, .exampleblock > .title, .imageblock > .title, .listingblock > .title, .literalblock > .title, .stemblock > .title, .openblock > .title, .paragraph > .title, .quoteblock > .title, table.tableblock > .title, .verseblock > .title, .videoblock > .title, .dlist > .title, .olist > .title, .ulist > .title, .qlist > .title, .hdlist > .title { text-rendering: optimizeLegibility; text-align: left; }

table.tableblock > caption.title { white-space: nowrap; overflow: visible; max-width: 0; }

.paragraph.lead > p, #preamble > .sectionbody > .paragraph:first-of-type p { color: black; }

table.tableblock #preamble > .sectionbody > .paragraph:first-of-type p { font-size: inherit; }

.admonitionblock > table { border-collapse: separate; border: 0; background: none; width: 100%; }
.admonitionblock > table td.icon { text-align: center; width: 80px; }
.admonitionblock > table td.icon img { max-width: initial; }
.admonitionblock > table td.icon .title { font-weight: bold; font-family: Noto, sans-serif; text-transform: uppercase; }
.admonitionblock > table td.content { padding-left: 1.125em; padding-right: 1.25em; border-left: 1px solid #dddddd; color: #5e93b8; }
.admonitionblock > table td.content > :last-child > :last-child { margin-bottom: 0; }

.exampleblock > .content { border-style: solid; border-width: 1px; border-color: #e6e6e6; margin-bottom: 1.25em; padding: 1.25em; background: white; -webkit-border-radius: 0; border-radius: 0; }
.exampleblock > .content > :first-child { margin-top: 0; }
.exampleblock > .content > :last-child { margin-bottom: 0; }

.sidebarblock { border-style: solid; border-width: 1px; border-color: #e6e6e6; margin-bottom: 1.25em; padding: 1.25em; background: white; -webkit-border-radius: 0; border-radius: 0; }
.sidebarblock > :first-child { margin-top: 0; }
.sidebarblock > :last-child { margin-bottom: 0; }
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<body class="manpage">
<div id="header">
<h1>imageReadFunctions(3) Manual Page</h1>
<h2 id="_name">Name</h2>
<div class="sectionbody">
<p>imageReadFunctions - Built-in Image Read Functions</p>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_description">Description</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The following built-in function calls to read images with a sampler<sup>58</sup> are
supported.</p>
</div>
<div class="paragraph">
<p>[58] The built-in function calls to read images with a sampler are not
supported for <code>image1d_buffer_t</code> image types.</p>
</div>
<table id="table-image-read" class="tableblock frame-all grid-all stretch">
<caption class="title">Table 1. Built-in Image Read Functions</caption>
<colgroup>
<col style="width: 50%;">
<col style="width: 50%;">
</colgroup>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>Function</strong></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>Description</strong></p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">float4 <strong>read_imagef</strong>(read_only image2d_t <em>image</em>, sampler_t <em>sampler</em>,
  int2 <em>coord</em>)<br>
  float4 <strong>read_imagef</strong>(read_only image2d_t <em>image</em>, sampler_t <em>sampler</em>,
  float2 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use the coordinate (<em>coord.x</em>, <em>coord.y</em>) to do an element lookup in
      the 2D image object specified by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [0.0, 1.0]
      for image objects created with <em>image_channel_data_type</em> set to one of
      the pre-defined packed formats or <code>CL_UNORM_INT8</code>, or
      <code>CL_UNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [-1.0, 1.0]
      for image objects created with <em>image_channel_data_type</em> set to
      <code>CL_SNORM_INT8</code>, or <code>CL_SNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values for image objects created
      with <em>image_channel_data_type</em> set to <code>CL_HALF_FLOAT</code> or <code>CL_FLOAT</code>.</p>
<p class="tableblock">      The <strong>read_imagef</strong> calls that take integer coordinates must use a
      sampler with filter mode set to <code>CLK_FILTER_NEAREST</code>, normalized
      coordinates set to <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode
      set to <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Values returned by <strong>read_imagef</strong> for image objects with
      <em>image_channel_data_type</em> values not specified in the description
      above are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">int4 <strong>read_imagei</strong>(read_only image2d_t <em>image</em>, sampler_t <em>sampler</em>,
  int2 <em>coord</em>)<br>
  int4 <strong>read_imagei</strong>(read_only image2d_t <em>image</em>, sampler_t <em>sampler</em>,
  float2 <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image2d_t <em>image</em>, sampler_t <em>sampler</em>,
  int2 <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image2d_t <em>image</em>, sampler_t <em>sampler</em>,
  float2 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use the coordinate (<em>coord.x</em>, <em>coord.y</em>) to do an element lookup in
      the 2D image object specified by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagei</strong> and <strong>read_imageui</strong> return unnormalized signed integer
      and unsigned integer values respectively.
      Each channel will be stored in a 32-bit integer.</p>
<p class="tableblock">      <strong>read_imagei</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_SIGNED_INT8</code>,<br>
      <code>CL_SIGNED_INT16</code> and<br>
      <code>CL_SIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imagei</strong> are undefined.</p>
<p class="tableblock">      <strong>read_imageui</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_UNSIGNED_INT8</code>,<br>
      <code>CL_UNSIGNED_INT16</code> and<br>
      <code>CL_UNSIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imageui</strong> are undefined.</p>
<p class="tableblock">      The <strong>read_image{i|ui}</strong> calls support a nearest filter only.
      The filter_mode specified in <em>sampler</em> must be set to
      <code>CLK_FILTER_NEAREST</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Furthermore, the <strong>read_image{i|ui}</strong> calls that take integer
      coordinates must use a sampler with normalized coordinates set to
      <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode set to
      <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">float4 <strong>read_imagef</strong>(read_only image3d_t <em>image</em>, sampler_t <em>sampler</em>,
  int4 <em>coord</em> )<br>
  float4 <strong>read_imagef</strong>(read_only image3d_t <em>image</em>, sampler_t <em>sampler</em>,
  float4 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use the coordinate (<em>coord.x</em>, <em>coord.y</em>, <em>coord.z</em>) to do an element
      lookup in the 3D image object specified by <em>image</em>.
      <em>coord.w</em> is ignored.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [0.0, 1.0]
      for image objects created with <em>image_channel_data_type</em> set to one of
      the pre-defined packed formats or <code>CL_UNORM_INT8</code>, or
      <code>CL_UNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [-1.0, 1.0]
      for image objects created with <em>image_channel_data_type</em> set to
      <code>CL_SNORM_INT8</code>, or <code>CL_SNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values for image objects created
      with <em>image_channel_data_type</em> set to <code>CL_HALF_FLOAT</code> or <code>CL_FLOAT</code>.</p>
<p class="tableblock">      The <strong>read_imagef</strong> calls that take integer coordinates must use a
      sampler with filter mode set to <code>CLK_FILTER_NEAREST</code>, normalized
      coordinates set to <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode
      set to <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Values returned by <strong>read_imagef</strong> for image objects with
      <em>image_channel_data_type</em> values not specified in the description are
      undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">int4 <strong>read_imagei</strong>(read_only image3d_t <em>image</em>, sampler_t <em>sampler</em>,
  int4 <em>coord</em>)<br>
  int4 <strong>read_imagei</strong>(read_only image3d_t <em>image</em>, sampler_t <em>sampler</em>,
  float4 <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image3d_t <em>image</em>, sampler_t <em>sampler</em>,
  int4 <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image3d_t <em>image</em>, sampler_t <em>sampler</em>,
  float4 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use the coordinate (<em>coord.x</em>, <em>coord.y</em>, <em>coord.z</em>) to do an element
      lookup in the 3D image object specified by <em>image</em>.
      <em>coord.w</em> is ignored.</p>
<p class="tableblock">      <strong>read_imagei</strong> and <strong>read_imageui</strong> return unnormalized signed integer
      and unsigned integer values respectively.
      Each channel will be stored in a 32-bit integer.</p>
<p class="tableblock">      <strong>read_imagei</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_SIGNED_INT8</code>,<br>
      <code>CL_SIGNED_INT16</code> and<br>
      <code>CL_SIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imagei</strong> are undefined.</p>
<p class="tableblock">      <strong>read_imageui</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_UNSIGNED_INT8</code>,<br>
      <code>CL_UNSIGNED_INT16</code> and<br>
      <code>CL_UNSIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imageui</strong> are undefined.</p>
<p class="tableblock">      The <strong>read_image{i|ui}</strong> calls support a nearest filter only.
      The filter_mode specified in <em>sampler</em> must be set to
      <code>CLK_FILTER_NEAREST</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Furthermore, the <strong>read_image{i|ui}</strong> calls that take integer
      coordinates must use a sampler with normalized coordinates set to
      <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode set to
      <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">float4 <strong>read_imagef</strong>(read_only image2d_array_t <em>image</em>,
  sampler_t <em>sampler</em>, int4 <em>coord</em>)<br>
  float4 <strong>read_imagef</strong>(read_only image2d_array_t <em>image</em>,
  sampler_t <em>sampler</em>, float4 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use <em>coord.xy</em> to do an element lookup in the 2D image identified by
      <em>coord.z</em> in the 2D image array specified by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [0.0, 1.0]
      for image objects created with image_channel_data_type set to one of
      the pre-defined packed formats or <code>CL_UNORM_INT8</code>, or
      <code>CL_UNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [-1.0, 1.0]
      for image objects created with image_channel_data_type set to
      <code>CL_SNORM_INT8</code>, or <code>CL_SNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values for image objects created
      with image_channel_data_type set to <code>CL_HALF_FLOAT</code> or <code>CL_FLOAT</code>.</p>
<p class="tableblock">      The <strong>read_imagef</strong> calls that take integer coordinates must use a
      sampler with filter mode set to <code>CLK_FILTER_NEAREST</code>, normalized
      coordinates set to <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode
      set to <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Values returned by <strong>read_imagef</strong> for image objects with
      image_channel_data_type values not specified in the description above
      are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">int4 <strong>read_imagei</strong>(read_only image2d_array_t <em>image</em>, sampler_t <em>sampler</em>,
  int4 <em>coord</em>)<br>
  int4 <strong>read_imagei</strong>(read_only image2d_array_t <em>image</em>, sampler_t <em>sampler</em>,
  float4 <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image2d_array_t <em>image</em>,
  sampler_t <em>sampler</em>, int4 <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image2d_array_t <em>image</em>,
  sampler_t <em>sampler</em>, float4 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use <em>coord.xy</em> to do an element lookup in the 2D image identified by
      <em>coord.z</em> in the 2D image array specified by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagei</strong> and <strong>read_imageui</strong> return unnormalized signed integer
      and unsigned integer values respectively.
      Each channel will be stored in a 32-bit integer.</p>
<p class="tableblock">      <strong>read_imagei</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_SIGNED_INT8</code>,<br>
      <code>CL_SIGNED_INT16</code> and<br>
      <code>CL_SIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imagei</strong> are undefined.</p>
<p class="tableblock">      <strong>read_imageui</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_UNSIGNED_INT8</code>,<br>
      <code>CL_UNSIGNED_INT16</code> and<br>
      <code>CL_UNSIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imageui</strong> are undefined.</p>
<p class="tableblock">      The <strong>read_image{i|ui}</strong> calls support a nearest filter only.
      The filter_mode specified in <em>sampler</em> must be set to
      <code>CLK_FILTER_NEAREST</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Furthermore, the <strong>read_image{i|ui}</strong> calls that take integer
      coordinates must use a sampler with normalized coordinates set to
      <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode set to
      <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">float4 <strong>read_imagef</strong>(read_only image1d_t <em>image</em>, sampler_t <em>sampler</em>,
  int <em>coord</em>)<br>
  float4 <strong>read_imagef</strong>(read_only image1d_t <em>image</em>, sampler_t <em>sampler</em>,
  float <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use <em>coord</em> to do an element lookup in the 1D image object specified
      by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [0.0, 1.0]
      for image objects created with <em>image_channel_data_type</em> set to one of
      the pre-defined packed formats or <code>CL_UNORM_INT8</code>, or
      <code>CL_UNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [-1.0, 1.0]
      for image objects created with <em>image_channel_data_type</em> set to
      <code>CL_SNORM_INT8</code>, or <code>CL_SNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values for image objects created
      with <em>image_channel_data_type</em> set to <code>CL_HALF_FLOAT</code> or <code>CL_FLOAT</code>.</p>
<p class="tableblock">      The <strong>read_imagef</strong> calls that take integer coordinates must use a
      sampler with filter mode set to <code>CLK_FILTER_NEAREST</code>, normalized
      coordinates set to <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode
      set to <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Values returned by <strong>read_imagef</strong> for image objects with
      <em>image_channel_data_type</em> values not specified in the description
      above are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">int4 <strong>read_imagei</strong>(read_only image1d_t <em>image</em>, sampler_t <em>sampler</em>,
  int <em>coord</em>)<br>
  int4 <strong>read_imagei</strong>(read_only image1d_t <em>image</em>, sampler_t <em>sampler</em>,
  float <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image1d_t <em>image</em>, sampler_t <em>sampler</em>,
  int <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image1d_t <em>image</em>, sampler_t <em>sampler</em>,
  float <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use <em>coord</em> to do an element lookup in the 1D image object specified
      by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagei</strong> and <strong>read_imageui</strong> return unnormalized signed integer
      and unsigned integer values respectively.
      Each channel will be stored in a 32-bit integer.</p>
<p class="tableblock">      <strong>read_imagei</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_SIGNED_INT8</code>,<br>
      <code>CL_SIGNED_INT16</code> and<br>
      <code>CL_SIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imagei</strong> are undefined.</p>
<p class="tableblock">      <strong>read_imageui</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_UNSIGNED_INT8</code>,<br>
      <code>CL_UNSIGNED_INT16</code> and<br>
      <code>CL_UNSIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imageui</strong> are undefined.</p>
<p class="tableblock">      The <strong>read_image{i|ui}</strong> calls support a nearest filter only.
      The filter_mode specified in <em>sampler</em> must be set to
      <code>CLK_FILTER_NEAREST</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Furthermore, the <strong>read_image{i|ui}</strong> calls that take integer
      coordinates must use a sampler with normalized coordinates set to
      <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode set to
      <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">float4 <strong>read_imagef</strong>(read_only image1d_array_t <em>image</em>,
  sampler_t <em>sampler</em>, int2 <em>coord</em>)<br>
  float4 <strong>read_imagef</strong>(read_only image1d_array_t <em>image</em>,
  sampler_t <em>sampler</em>, float2 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use <em>coord.x</em> to do an element lookup in the 1D image identified by
      <em>coord.y</em> in the 1D image array specified by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [0.0, 1.0]
      for image objects created with image_channel_data_type set to one of
      the pre-defined packed formats or <code>CL_UNORM_INT8</code>, or
      <code>CL_UNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values in the range [-1.0, 1.0]
      for image objects created with image_channel_data_type set to
      <code>CL_SNORM_INT8</code>, or <code>CL_SNORM_INT16</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns floating-point values for image objects created
      with image_channel_data_type set to <code>CL_HALF_FLOAT</code> or <code>CL_FLOAT</code>.</p>
<p class="tableblock">      The <strong>read_imagef</strong> calls that take integer coordinates must use a
      sampler with filter mode set to <code>CLK_FILTER_NEAREST</code>, normalized
      coordinates set to <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode
      set to <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Values returned by <strong>read_imagef</strong> for image objects with
      image_channel_data_type values not specified in the description above
      are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">int4 <strong>read_imagei</strong>(read_only image1d_array_t <em>image</em>, sampler_t <em>sampler</em>,
  int2 <em>coord</em>)<br>
  int4 <strong>read_imagei</strong>(read_only image1d_array_t <em>image</em>, sampler_t <em>sampler</em>,
  float2 <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image1d_array_t <em>image</em>,
  sampler_t <em>sampler</em>, int2 <em>coord</em>)<br>
  uint4 <strong>read_imageui</strong>(read_only image1d_array_t <em>image</em>,
  sampler_t <em>sampler</em>, float2 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use <em>coord.x</em> to do an element lookup in the 1D image identified by
      <em>coord.y</em> in the 1D image array specified by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagei</strong> and <strong>read_imageui</strong> return unnormalized signed integer
      and unsigned integer values respectively. Each channel will be stored
      in a 32-bit integer.</p>
<p class="tableblock">      <strong>read_imagei</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_SIGNED_INT8</code>,<br>
      <code>CL_SIGNED_INT16</code> and<br>
      <code>CL_SIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imagei</strong> are undefined.</p>
<p class="tableblock">      <strong>read_imageui</strong> can only be used with image objects created with
      <em>image_channel_data_type</em> set to one of the following values:</p>
<p class="tableblock">      <code>CL_UNSIGNED_INT8</code>,<br>
      <code>CL_UNSIGNED_INT16</code> and<br>
      <code>CL_UNSIGNED_INT32</code>.</p>
<p class="tableblock">      If the <em>image_channel_data_type</em> is not one of the above values, the
      values returned by <strong>read_imageui</strong> are undefined.</p>
<p class="tableblock">      The <strong>read_image{i|ui}</strong> calls support a nearest filter only.
      The filter_mode specified in <em>sampler</em> must be set to
      <code>CLK_FILTER_NEAREST</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Furthermore, the <strong>read_image{i|ui}</strong> calls that take integer
      coordinates must use a sampler with normalized coordinates set to
      <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode set to
      <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>read_imagef</strong>(read_only image2d_depth_t <em>image</em>,
  sampler_t <em>sampler</em>, int2 <em>coord</em>)<br>
  float <strong>read_imagef</strong>(read_only image2d_depth_t <em>image</em>,
  sampler_t <em>sampler</em>, float2 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use the coordinate (<em>coord.x</em>, <em>coord.y</em>) to do an element lookup in
      the 2D depth image object specified by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns a floating-point value in the range [0.0, 1.0]
      for depth image objects created with <em>image_channel_data_type</em> set to
      <code>CL_UNORM_INT16</code> or <code>CL_UNORM_INT24</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns a floating-point value for depth image objects
      created with <em>image_channel_data_type</em> set to <code>CL_FLOAT</code>.</p>
<p class="tableblock">      The <strong>read_imagef</strong> calls that take integer coordinates must use a
      sampler with filter mode set to <code>CLK_FILTER_NEAREST</code>, normalized
      coordinates set to <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode
      set to <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Values returned by <strong>read_imagef</strong> for depth image objects with
      <em>image_channel_data_type</em> values not specified in the description
      above are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>read_imagef</strong>(read_only image2d_array_depth_t <em>image</em>,
  sampler_t <em>sampler</em>, int4 <em>coord</em>)<br>
  float <strong>read_imagef</strong>(read_only image2d_array_depth_t <em>image</em>,
  sampler_t <em>sampler</em>, float4 <em>coord</em>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Use <em>coord.xy</em> to do an element lookup in the 2D image identified by
      <em>coord.z</em> in the 2D depth image array specified by <em>image</em>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns a floating-point value in the range [0.0, 1.0]
      for depth image objects created with <em>image_channel_data_type</em> set to
      <code>CL_UNORM_INT16</code> or <code>CL_UNORM_INT24</code>.</p>
<p class="tableblock">      <strong>read_imagef</strong> returns a floating-point value for depth image objects
      created with <em>image_channel_data_type</em> set to <code>CL_FLOAT</code>.</p>
<p class="tableblock">      The <strong>read_imagef</strong> calls that take integer coordinates must use a
      sampler with filter mode set to <code>CLK_FILTER_NEAREST</code>, normalized
      coordinates set to <code>CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode
      set to <code>CLK_ADDRESS_CLAMP_TO_EDGE</code>, <code>CLK_ADDRESS_CLAMP</code> or
      <code>CLK_ADDRESS_NONE</code>; otherwise the values returned are undefined.</p>
<p class="tableblock">      Values returned by <strong>read_imagef</strong> for image objects with
      <em>image_channel_data_type</em> values not specified in the description
      above are undefined.</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"></td>
<td class="tableblock halign-left valign-top"></td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="sect1">
<h2 id="_see_also">See Also</h2>
<div class="sectionbody">
<div class="paragraph">
<p><a href="imageQueryFunctions.html">imageQueryFunctions</a>, <a href="imageSamplerlessReadFunctions.html">imageSamplerlessReadFunctions</a>, <a href="imageWriteFunctions.html">imageWriteFunctions</a></p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_document_notes">Document Notes</h2>
<div class="sectionbody">
<div class="paragraph">
<p>For more information, see the <a href="https://www.khronos.org/registry/OpenCL/specs/2.2/html/OpenCL_C.html#built-in-image-read-functions" target="_blank" rel="noopener">OpenCL C Specification</a></p>
</div>
<div class="paragraph">
<p>This page is extracted from the OpenCL C Specification.
Fixes and changes should be made to the Specification, not directly.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_copyright">Copyright</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Copyright (c) 2014-2020 Khronos Group. This work is licensed under a
<a href="http://creativecommons.org/licenses/by/4.0/" target="_blank" rel="noopener">Creative Commons
Attribution 4.0 International License</a>.</p>
</div>
</div>
</div>
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