Name

    INGR_interlace_read

Name Strings

    GL_INGR_interlace_read

Version

    Date: 12/14/98    Revision: 1.0

Number

    175

Dependencies

    None

Overview

    This extension provides a way to skip rows of pixels when reading
    or copying pixel rectangles.  This extension is complementary to
    the EXT_interlace extension except that it has no affect on getting
    texture images.

New Procedures and Functions

    None

New Tokens

    Accepted by the <cap> parameter of of Enable, Disable, IsEnabled, and
    by the <pname> parameter of GetBooleanv, GetIntegerv, GetFloatv,
    GetDoublev:

      INTERLACE_READ_INGR                   0x8568

Additions to Chapter 2 of the 1.2 Specification (OpenGL Operation)

    None

Additions to Chapter 3 of the 1.2 Specification (Rasterization)

    None

Additions to Chapter 4 of the 1.2 Specification (Per-Fragment Operations
and the Frame Buffer)

    [In section 4.3.2 "Reading Pixels" the specification of an interlace
    read operation is added to the GL Specification in the sectino on
    "Obtaining Pixels from the FrameBuffer."]

    Reading interlaced rows of pixels is enabled or disabled with Enable
    or Disable using the symbolic constant INTERLACE_READ_INGR.  If
    INTERLACE_READ_INGR is disabled, then ReadPixels obtains values from
    the selected buffer from each pixel with lower left hand corner at
    (x+i, y+j) for 0 <= i < width and 0 <= j < height; this pixel is said
    to be the ith pixel in the jth row.

    If INTERLACE_READ_INGR is enabled, then ReadPixels obtains values
    from the selected buffer from each pixel with lower left hand corner
    at (x+i, y+(j*2)) for 0 <= i < width and 0 <= j < height; this pixel
    is said to be the ith pixel in the jth row.

    If any of these pixels lies outside of the window...

Additions to Chapter 5 of the 1.2 Specification (Special Functions)

    None

Additions to Chapter 6 of the 1.2 Specification (State and State Requests)

    None

Additions to the GLX Specification

    None

Errors

    None

New State

    Get Value              Get Command        Type    Initial Value    Attribute
    --------------------   ---------------    -----   --------------   -------------
    INTERLACE_READ_INGR     IsEnabled          B       False            pixel/enable

New Implementation Dependent State

    None