skia / external / github.com / KhronosGroup / OpenGL-Registry / d15191e446614fcec3369577495dfb45b131a27a / . / extensions / EXT / EXT_pixel_transform.txt

Name | |

EXT_pixel_transform | |

Name Strings | |

GL_EXT_pixel_transform | |

Version | |

$Date: 1997/10/17 02:08:51 $ $Revision: 1.2 $ | |

Number | |

138 | |

Dependencies | |

None | |

Overview | |

This extension provides support for scaling, rotation, translation and | |

shearing of two-dimensional pixel rectangles in the pixel rasterizer. | |

The transformation is defined via a 4x4 matrix, where only those entries | |

which apply as a 2D affine transformation will be accepted and used. | |

These matrices can be manipulated using the same functions as the other | |

OpenGL matrix stacks. | |

New Procedures and Functions | |

void PixelTransformParameteriEXT(enum target, | |

enum pname, | |

const int param) | |

void PixelTransformParameterfEXT(enum target, | |

enum pname, | |

const float param) | |

void PixelTransformParameterivEXT(enum target, | |

enum pname, | |

const int* params) | |

void PixelTransformParameterfvEXT(enum target, | |

enum pname, | |

const float* params) | |

These routines are used to set pixel transformation attributes. | |

The only allowable value for <target> at this time is | |

PIXEL_TRANSFORM_2D_EXT. Allowable values for <pname> include: | |

PIXEL_MAG_FILTER_EXT, PIXEL_MIN_FILTER_EXT, and PIXEL_CUBIC_WEIGHT_EXT. | |

void GetPixelTransformParameterivEXT(enum target, | |

enum pname, | |

const int* params) | |

void GetPixelTransformParameterfvEXT(enum target, | |

enum pname, | |

const float* params) | |

These routines are used to query pixel transformation attributes. | |

The only allowable value for <target> at this time is | |

PIXEL_TRANSFORM_2D_EXT. Allowable values for <pname> include: | |

PIXEL_MAG_FILTER_EXT, PIXEL_MIN_FILTER_EXT, and PIXEL_CUBIC_WEIGHT_EXT. | |

New Tokens | |

Accepted by the <pname> parameter of PixelTransformParameteri, | |

PixelTransformParameterf, PixelTransformParameteriv, | |

PixelTransformParameterfv, GetPixelTransformParameteriv and | |

GetPixelTransformParameterfv: | |

PIXEL_MAG_FILTER_EXT 0x8331 | |

PIXEL_MIN_FILTER_EXT 0x8332 | |

PIXEL_CUBIC_WEIGHT_EXT 0x8333 | |

Accepted by the <params> parameter of PixelTransformParameteriEXT, | |

PixelTransformParameterfEXT, PixelTransformParameterivEXT, and | |

PixelTransformParameterfvEXT when <pname> is PIXEL_MAG_FILTER_EXT | |

or PIXEL_MIN_FILTER_EXT: | |

CUBIC_EXT 0x8334 | |

Accepted by the <params> parameter of PixelTransformParameteriEXT, | |

PixelTransformParameterfEXT, PixelTransformParameterivEXT, and | |

PixelTransformParameterfvEXT when <pname> is PIXEL_MIN_FILTER_EXT: | |

AVERAGE_EXT 0x8335 | |

Accepted by the <mode> parameter of MatrixMode, | |

and by the <target> parameter of PixelTransformParameterivEXT, | |

PixelTransformParameterfvEXT, GetPixelTransformParameterivEXT, | |

and GetPixelTransformParameterfvEXT: | |

PIXEL_TRANSFORM_2D_EXT 0x8330 | |

Accepted by the <pname> parameter of GetIntegerv, GetFloatv, | |

and GetDoublev: | |

PIXEL_TRANSFORM_2D_STACK_DEPTH_EXT 0x8336 | |

MAX_PIXEL_TRANSFORM_2D_STACK_DEPTH_EXT 0x8337 | |

Accepted by the <pname> parameter of GetFloatv, and GetDoublev: | |

PIXEL_TRANSFORM_2D_MATRIX_EXT 0x8338 | |

Additions to Chapter 2 of the 1.1 Specification (OpenGL Operation) | |

In section 2.10.2 "Matrices": | |

The projection matrix, model-view matrix and pixel-transform matrix | |

are set and modified with a variety of commands. The affected matrix is | |

determined by the current matrix mode. The current matrix mode is set with | |

void MatrixMode (enum mode); | |

which takes one of the four pre-defined constants TEXTURE, MODELVIEW, | |

PROJECTION, or PIXEL_TRANSFORM_2D_EXT as the argument value. TEXTURE is | |

described later. If the current matrix mode is MODELVIEW, then matrix | |

operations apply to the model-view matrix; if PROJECTION, then they apply | |

to the projection matrix; if PIXEL_TRANSFORM_2D_EXT, then they apply to | |

the pixel-transform matrix. | |

Additions to Chapter 3 of the 1.1 Specification (Rasterization) | |

The specification of two-dimensional pixel transformation operators | |

is defined in the GL specification in the final subsection of | |

Section 3.6.3, "Conversion to Fragments." The following paragraphs | |

replace the text of the subsection. | |

The conversion of a group to fragments is controlled by the pixel | |

transformation matrix. The pixel transformation matrix is defined | |

by calling MatrixMode with <mode> set to PIXEL_TRANSFORM_2D_EXT, then using | |

any of the existing functions which operate on matrices and matrix stacks. | |

(i.e. LoadIdentity, LoadMatrix, MultMatrix, PushMatrix, PopMatrix, Rotate, | |

Scale, and Translate.) When using the matrix operators, while in | |

PIXEL_TRANSFORM_2D_EXT matrix mode, those entries in the 4 x 4 matrix | |

that are not part of a 2D affine transformation are forced to take on | |

values of either 0 or 1 so that the final matrix represents a 2D affine | |

transformation matrix. That is to say, of the matrix entries shown below: | |

-- -- | |

| m0 m4 m8 m12| | |

P = | m1 m5 m9 m13| | |

| m2 m6 m10 m14| | |

| m3 m7 m11 m15| | |

-- -- | |

only the matrix entries m0, m1, m4, m5, m12, and m13 are allowed to | |

vary. The other matrix entries will be forced to be either 0 or 1 as | |

shown below: | |

-- -- | |

| m0 m4 0 m12| | |

P = | m1 m5 0 m13| | |

| 0 0 1 0 | | |

| 0 0 0 1 | | |

-- -- | |

The pixel transformation operation is always enabled. The pixel | |

transformation operation uses the current pixel transformation | |

matrix to compute new window coordinates for each incoming pixel. | |

Resampling occurs after the pixel transformation matrix has been | |

applied. | |

Window coordinates are computed for each group by multiplying | |

the column/row location in the original pixel rectangle by the pixel | |

transformation matrix. The components of the current raster position | |

(section 2.12) are then added to the resulting components. (If the | |

current raster position is invalid, then DrawPixels is | |

ignored.) Let (Xrp, Yrp) be the current raster position and let | |

(Xo, Yo) represent the column and row of the group in the original | |

pixel rectangle. The depth value (Z) for the group is defined | |

as the depth value at the original location in the pixel rectangle | |

if the format was DEPTH_COMPONENT, and as the depth associated with | |

the current raster position otherwise. The final transformed pixel | |

coordinate (Xf, Yf, Zf) is computed by: | |

-- -- -- -- | |

| Xo | | Xt | | |

| Yo | P = | Yt | | |

| Z | | Zt | | |

| 1 | | 1 | | |

-- -- -- -- | |

Xf = Xt + Xrp | |

Yf = Yt + Yrp | |

Zf = Zt | |

The function | |

void PixelZoom( float zx, float zy ) ; | |

will set the current pixel transformation matrix (the current top | |

of the pixel transformation matrix stack) to the scaling matrix: | |

-- -- | |

| zx 0 0 0 | | |

P = | 0 zy 0 0 | | |

| 0 0 1 0 | | |

| 0 0 0 1 | | |

-- -- | |

The original pixel value for each input pixel location is left unmodified | |

by the pixel transformation. Since multiple input pixels can be mapped | |

into a single output pixel (minification of the input pixel rectangle), | |

or since output pixels might not have any input pixels mapped to them | |

(magnification of input pixel rectangle), some method of resampling | |

is required. Resampling methods are set using the functions | |

PixelTransformParameteriEXT, PixelTransformParameterfEXT, | |

PixelTransformParameterivEXT, or PixelTransformParameterfvEXT with | |

<target> set to PIXEL_TRANSFORM_2D_EXT. | |

The resampling method to be used when the pixel rectangle is | |

magnified is specified by calling one of these functions with | |

<pname> set to PIXEL_MAG_FILTER_EXT and <params> set to NEAREST, | |

LINEAR, or CUBIC_EXT. The resampling method to be used when the | |

pixel rectangle is minified is specified by calling one of these | |

functions with <pname> set to PIXEL_MIN_FILTER_EXT and <params> | |

set to NEAREST, LINEAR, CUBIC_EXT, or AVERAGE_EXT. | |

PIXEL_CUBIC_WEIGHT_EXT defines the cubic weighting coefficient | |

that is to be used whenever the resampling technique is set to CUBIC_EXT. | |

If the resampling method is NEAREST, each output pixel will have the | |

value of the input pixel whose transformed coordinate value is nearest | |

(in Manhattan distance). If the resampling method is LINEAR, each | |

output pixel will have a value that is the weighted average of the | |

four input pixels whose transformed coordinate values are nearest. | |

If the resampling method is CUBIC_EXT, each output pixel will have a value | |

that is affected by the 16 input pixels whose transformed coordinate | |

values are nearest. The 16 input pixels will be used to perform a cubic | |

spline interpolation to determine the value of the output pixel. The | |

cubic weight factor is a floating point value that is applied to the | |

cubic interpolation in the manner described in "Digital Image Warping" | |

by George Wolberg (IEEE Computer Society Press, ISBN 0-8186-8944-7). | |

Visually pleasing cubic weighting values are typically in the | |

range [-1,0]. The values -1.0 and -0.5 are most commonly used. | |

For the purpose of performing bicubic interpolation along the outer | |

edge of the pixel rectangle, the outermost one pixel edge of the pixel | |

rectangle is duplicated prior to performing the interpolation along the | |

edges. | |

If the resampling method is AVERAGE_EXT, the values of all of the input | |

pixels that contribute to the final output pixel will be averaged to | |

determine the final output pixel value. That is to say, an output pixel | |

is backward mapped into the input pixel rectangle, then the nearest | |

neighbor resampling method determines the address of the center input | |

pixel from which input pixels will be averaged. All pixels in the input | |

that forward map into the same location in the output pixel rectangle will | |

be added together and divided by the total number of input pixels which | |

contribute the same output pixel. An example would be, if the output | |

pixel rectangle is 1/3 the size of the input pixel rectangle, then a | |

total of 9 pixels would be read from the input pixel rectangle, averaged, | |

and then the new single value will be written into the output pixel | |

rectangle. | |

Pixel transformation is defined for pixel rectangles that contain INDEX, | |

LUMINANCE, LUMINANCE_ALPHA, RGB, RGBA, or ABGR_EXT components or depth | |

components in pixel rastorization. Groups arising from DrawPixels with | |

a format of STENCIL_INDEX are treated specially and are described in | |

section 4.3.1. | |

A fragment arising from a group consisting of color data takes on the | |

color index or color components of the group; the depth and texture | |

coordinates are taken from the current raster position's associated | |

data. A fragment arising from a depth component takes the component's | |

depth value; the color and texture coordinates are given by those | |

associated with the current raster position. In both cases texture | |

coordinates s, t, and r are replaced with s/q, t/q, and r/q, | |

respectively. | |

Additions to Chapter 4 of the 1.1 Specification (Per-Fragment Operations | |

and the Frame Buffer) | |

The pixel transformation operation occurs in pixel rasterization | |

immediately after the operations in the pixel transfer pipeline. | |

The operation of pixel transformation during pixel copy | |

operations is identical to the operation during pixel drawing. | |

The pixel transformation is not applied during pixel query | |

operations. | |

Additions to Chapter 5 of the 1.1 Specification (Special Functions) | |

GetPixelTransformParameterivEXT, and GetPixelTransformParameterfvEXT | |

are not included in display lists, but are instead executed immediately. | |

Additions to Chapter 6 of the 1.1 Specification (State and State Requests) | |

Integer and floating point query functions GetPixelTransformParameterivEXT | |

and GetPixelTransformParameterfvEXT are provided. <target> must be | |

PIXEL_TRANSFORM_2D_EXT. <pname> is one of PIXEL_MAG_FILTER_EXT, | |

PIXEL_MIN_FILTER_EXT, or PIXEL_CUBIC_WEIGHT_EXT. The value of the | |

specified parameter is returned in <params>. | |

Additions to the GLX Specification | |

None | |

GLX Protocol | |

Four new GL commands are added. | |

The following two rendering commands are sent to the server as part of | |

a glXRender request: | |

PixelTransformParameterfEXT | |

2 16 rendering command length | |

2 16385 rendering command opcode | |

4 ENUM target | |

4 ENUM pname | |

4 FLOAT32 param | |

PixelTransformParameteriEXT | |

2 16 rendering command length | |

2 16386 rendering command opcode | |

4 ENUM target | |

4 ENUM pname | |

4 INT32 param | |

The remaining two commands are non-rendering commands. These commands | |

are sent seperately (i.e., not as part of a glXRender or | |

glXRenderLarge request), using the glXVendorPrivateWithReply | |

request: | |

GetPixelTransformParameterfvEXT | |

1 CARD8 opcode (X assigned) | |

1 17 GLX opcode (glXVendorPrivateWithReply) | |

2 5 request length | |

4 2051 vendor specific opcode | |

4 GLX_CONTEXT_TAG context tabg | |

4 ENUM target | |

4 ENUM pname | |

==> | |

1 1 reply | |

1 unused | |

2 CARD16 sequence number | |

4 m reply length, m = (n==1 ? 0: n) | |

4 unused | |

4 CARD16 n (0 or 1) | |

if (n=1) this follows: | |

4 FLOAT32 params | |

12 unused | |

Note that n may be zero, indicating that a GL error occurred. | |

GetPixelTransformParameterivEXT | |

1 CARD8 opcode (X assigned) | |

1 17 GLX opcode (glXVendorPrivateWithReply) | |

2 5 request length | |

4 2052 vendor specific opcode | |

4 GLX_CONTEXT_TAG context tabg | |

4 ENUM target | |

4 ENUM pname | |

==> | |

1 1 reply | |

1 unused | |

2 CARD16 sequence number | |

4 m reply length, m = (n==1 ? 0: n) | |

4 unused | |

4 CARD16 n (0 or 1) | |

if (n=1) this follows: | |

4 INT32 params | |

12 unused | |

Note that n may be zero, indicating that a GL error occurred. | |

Errors | |

INVALID_ENUM is generated if PixelTransformParameteriEXT, | |

PixelTransformParameterfEXT, PixelTransformParameterivEXT, | |

PixelTransformParameterfvEXT, GetPixelTransformParameterivEXT, | |

or GetPixelTransformParameterfvEXT is called with <target> set to | |

a value other than PIXEL_TRANSFORM_2D_EXT. | |

INVALID_ENUM is generated if GetPixelTransformParameterivEXT or | |

GetPixelTransformParameterfvEXT is called with <pname> set to | |

PIXEL_MAG_FILTER_EXT and <params> is not one of NEAREST, LINEAR, | |

or CUBIC_EXT. | |

INVALID_ENUM is generated if GetPixelTransformParameterivEXT or | |

GetPixelTransformParameterfvEXT is called with <pname> set to | |

PIXEL_MIN_FILTER_EXT and <params> is not one of NEAREST, LINEAR, | |

CUBIC_EXT, or AVERAGE_EXT. | |

INVALID_VALUE is generated if PixelTransformParameteriEXT, | |

PixelTransformParameterfEXT, PixelTransformParameterivEXT, or | |

PixelTransformParameterfvEXT is called with <pname> set to | |

PIXEL_CUBIC_WEIGHT_EXT and <params> is a value outside of | |

the range [-1, 0]. | |

INVALID_OPERATION is generated if PixelTransformParameteriEXT, | |

PixelTransformParameterfEXT, PixelTransformParameterivEXT, | |

PixelTransformParameterfvEXT, GetPixelTransformParameterivEXT, | |

or GetPixelTransformParameterfvEXT is called between execution of | |

Begin and the corresponding execution of End. | |

New State | |

Initial | |

Get Value Get Command Type Value Attrib | |

--------- ----------- ---- ------- ------ | |

PIXEL_TRANSFORM_2D_STACK_DEPTH_EXT GetIntegerv I 1 - | |

PIXEL_TRANSFORM_2D_STACK_DEPTH_EXT GetFloatv R 1 - | |

PIXEL_TRANSFORM_2D_STACK_DEPTH_EXT GetDoublev D 1 - | |

MAX_PIXEL_TRANSFORM_2D_STACK_DEPTH_EXT GetIntegerv I 32 - | |

MAX_PIXEL_TRANSFORM_2D_STACK_DEPTH_EXT GetFloatv R 32 - | |

MAX_PIXEL_TRANSFORM_2D_STACK_DEPTH_EXT GetDoublev D 32 - | |

PIXEL_TRANSFORM_2D_MATRIX_EXT GetFloatv 16 x R Identity - | |

PIXEL_TRANSFORM_2D_MATRIX_EXT GetDoublev 16 x D Identity - | |

PIXEL_MAG_FILTER_EXT GetPixelTransformParameteri Z3 NEAREST pixel | |

PIXEL_MIN_FILTER_EXT GetPixelTransformParameteri Z4 NEAREST pixel | |

PIXEL_CUBIC_WEIGHT_EXT GetPixelTransformParameterf R -1 pixel | |

New Implementation Dependent State | |

None | |