xref: /third_party/openGLES/extensions/APPLE/APPLE_texture_format_BGRA8888.txt

Name

    APPLE_texture_format_BGRA8888

Name Strings

    GL_APPLE_texture_format_BGRA8888

Contact

    Benj Lipchak, Apple (lipchak 'at' apple.com)

IP Status

    No known IP issues.

Status

    Complete.

Version

    Last Modified Date: June 26, 2013
    Revision: 3

Number

    OpenGL ES Extension #79

Dependencies

    Written based on the wording of the OpenGL ES 1.1 specification.
    There are interactions with OpenGL ES 3.0 or EXT_texture_storage.

Overview

    This extension introduces BGRA_EXT as an acceptable external format.  
    This avoids byte swizzling when loading RGBA internal format
    textures, which may be stored in BGRA order internally.

Issues

    None.

New Procedures and Functions

    None.

New Tokens

    Accepted by the <format> parameters of TexImage2D and TexSubImage2D:

        GL_BGRA_EXT                                 0x80E1

    Accepted by the <internalformat> parameters of TexStorage2D and 
    TexStorage3D:

        GL_BGRA8_EXT                                0x93A1

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

    None

Additions to Chapter 3 of the OpenGL ES 1.1 Specification (Rasterization)

    Section 3.6.2, add the following row to Table 3.3:
    
        Format Name    Element Meaning and Order    Target Buffer
        -----------    -------------------------    -------------
        BGRA_EXT       B, G, R, A                   Color

    Section 3.6.2, add the following row to Table 3.4:
    
        Format      Type             Bytes per Pixel
        --------    -------------    ---------------
        BGRA_EXT    UNSIGNED_BYTE    4

    Section 3.7.1, change the 4th paragraph to loosen the requirement that
    <internalformat> must match <format> for the case of BGRA_EXT format, which
    must have an RGBA internal format.  In this case we do not generate the
    error INVALID_OPERATION.

Additions to Chapter 4 of the OpenGL ES 1.1 Specification (Per-Fragment Operations and the Framebuffer)

    None

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

    None

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

    None

Dependencies on OpenGL ES 3.0 or EXT_texture_storage

    When the GL is OpenGL ES 3.0, the following table entry is added to
    Table 3.2:
    
        Format    Type           External Bytes per Pixel  Internal Format
        --------  -------------  ------------------------  ---------------
        BGRA_EXT  UNSIGNED_BYTE  4                         BGRA8_EXT

    When the GL is OpenGL ES 3.0, BGRA8_EXT is also added to the Texture-only 
    color formats list in the Required Texture Formats subsection of section 
    3.8.3.

    If the GL is not OpenGL ES 3.0 and the EXT_texture_storage extension is not
    present, omit references to BGRA8_EXT and TexStorage*.
    
    Note that despite TexStorage* being defined in terms of TexImage*, 
    BGRA8_EXT is not accepted as an <internalformat> parameter to TexImage* 
    when the GL is OpenGL ES 3.0.
    
    Details of how this extension interacts with EXT_texture_storage when the 
    GL is a version of OpenGL earlier than 3.0 can be found in the 
    EXT_texture_storage spec.

Errors

    INVALID_ENUM is generated by TexImage2D if <internalformat> is BGRA_EXT.

    INVALID_OPERATION is generated by TexImage2D if <format> is BGRA_EXT and
    <internalformat> is not RGBA.

New State

    None

New Implementation Dependent State

    None

Revision History

    #3  06/26/2013    Benj Lipchak     Add ES3 interactions
    #2  10/27/2009    Benj Lipchak     Add EXT suffix to BGRA token
    #1  05/14/2009    Benj Lipchak     First draft