gpu/GLES2/extensions/CHROMIUM/CHROMIUM_flipy.txt

Name

    CHROMIUM_flipy

Name Strings

    GL_CHROMIUM_flipy

Version

    Last Modifed Date: April 9, 2012

Dependencies

    OpenGL ES 2.0 is required.

Overview

    This extension adds the ability to vertically flip texture image data when
    calling TexImage2D and TexSubImage2D.

Issues


New Tokens

    Accepted by the <param> parameter of PixelStorei:

        UNPACK_FLIP_Y_CHROMIUM              0x9240

Additions to the OpenGL ES 2.0 Specification

    Modifications to Table 3.1 (PixelStore Parameters)

        Add the following entry:

        Parameter Name                   Type      Initial Value  Valid Range
        ==============                   ====      =============  ===========
        UNPACK_FLIP_Y_CHROMIUM           boolean   FALSE          {TRUE, FALSE}

    Modifications to 3.6.2 Transfer of Pixel Rectangles, in the Unpacking
    section:

    Change
        "If p indicates the location in memory of the first element of the first
        row, then the first element of the Nth row is indicated by
                            p + Nk (3.9)"
    to
        "If p indicates the location in memory of the first element of the first
        row, then the first element of the Nth row is indicated by
                            p + Nk (3.9)
        if UNPACK_FLIP_Y is FALSE. Otherwise, the first element of the Nth row
        is indicated by
                            p - Nk (3.10)

    After the sentence

        "If the number of bits per element is not 1, 2, 4, or 8 times the number
        of bits in a GL ubyte, then k = nl for all values of a."

    insert:

        "If UNPACK_FLIP_Y_CHROMIUM is FALSE then p is equal to pixels. Otherwise
        p is pixels + (height - 1)k."

Interactions with GL_EXT_unpack_subimage

    Do not add the sentence "If UNPACK_FLIP_Y_CHROMIUM is FALSE ..." described
    in this extension. Instead do the following after applying
    GL_EXT_unpack_subimage:

    Change

         "There is a mechanism for selecting a sub-rectangle of groups
          from a larger containing rectangle. This mechanism relies on
          three integer parameters: UNPACK_ROW_LENGTH, UNPACK_SKIP_ROWS,
          and UNPACK_SKIP_PIXELS. Before obtaining the first group from
          memory, the pointer supplied to TexImage2D is effectively
          advanced by (UNPACK_SKIP_PIXELS)n + (UNPACK_SKIP_ROWS)k
          elements. Then <width> groups are obtained from contiguous
          elements in memory (without advancing the pointer), after
          which the pointer is advanced by k elements. <height> sets of
          <width> groups of values are obtained this way. See figure
          3.6."

    to

         "There is a mechanism for selecting a sub-rectangle of groups
          from a larger containing rectangle. This mechanism relies on
          three integer parameters: UNPACK_ROW_LENGTH, UNPACK_SKIP_ROWS,
          and UNPACK_SKIP_PIXELS. IF UNPACK_FLIP_Y_CHROMIUM is FALSE then
          p, the location of the first element of the first
          group, is pixels + (UNPACK_SKIP_PIXELS)n + (UNPACK_SKIP_ROWS)k.
          When UNPACK_FLIP_Y_CHROMIUM is TRUE then p is pixels +
          (UNPACK_SKIP_PIXELS)n + (UNPACK_SKIP_ROWS + height - 1)k. After
          p is determined <width> groups are obtained from contiguous
          elements in memory (without advancing the pointer), after which
          the pointer is advanced by +/-k elements depending on the value
          of UNPACK_CHROMIUM_FLIP_Y. <height> sets of <width> groups of
          values are obtained this way. See figure 3.6."

New Procedures and Functions

    None.

Errors

    None.

New State

    None.

Revision History

    7/22/2011    Documented the extension
    4/09/2012    Added more documentation and described interactions with
                 GL_EXT_unpack_subimage