WebGL WEBGL_compressed_texture_astc Extension Specification

Name

WEBGL_compressed_texture_astc

Contact

WebGL working group (public_webgl 'at' khronos.org)

Contributors

Christophe Riccio, Unity

Members of the WebGL working group

Version

Last modified date: December 12, 2016
Revision: 5

Number

WebGL extension #30

Dependencies

Written against the WebGL API 1.0 specification.

Overview

This extension exposes the compressed texture format defined in the KHR_texture_compression_astc_hdr OpenGL ES extension to WebGL. Consult that extension specification for behavioral definitions, including error behaviors.

ASTC textures may be encoded using either high or low dynamic range, corresponding to an "HDR profile" and "LDR profile". The compression format is designed to be extended, and for new profiles to be added in the future. For this reason, enabling the WebGL extension enables all of the profiles supported by the implementation. The supported profiles may be queried by calling getSupportedProfiles against the extension object.

When this extension is enabled:

• Compression format COMPRESSED_RGBA_ASTC_4x4_KHR, COMPRESSED_RGBA_ASTC_5x4_KHR, COMPRESSED_RGBA_ASTC_5x5_KHR, COMPRESSED_RGBA_ASTC_6x5_KHR, COMPRESSED_RGBA_ASTC_6x6_KHR, COMPRESSED_RGBA_ASTC_8x5_KHR, COMPRESSED_RGBA_ASTC_8x6_KHR, COMPRESSED_RGBA_ASTC_8x8_KHR, COMPRESSED_RGBA_ASTC_10x5_KHR, COMPRESSED_RGBA_ASTC_10x6_KHR, COMPRESSED_RGBA_ASTC_10x8_KHR, COMPRESSED_RGBA_ASTC_10x10_KHR, COMPRESSED_RGBA_ASTC_12x10_KHR, COMPRESSED_RGBA_ASTC_12x12_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_4x4_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_5x4_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_5x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_6x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_6x6_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_8x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_8x6_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_8x8_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x6_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x8_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x10_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_12x10_KHR, and COMPRESSED_SRGB8_ALPHA8_ASTC_12x12_KHR may be passed to the compressedTexImage2D and compressedTexSubImage2D entry points.
• Calling getParameter with the argument COMPRESSED_TEXTURE_FORMATS will include the format from this specification.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_4x4_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_4x4_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 3) / 4) * floor((height + 3) / 4) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_5x4_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_5x4_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 4) / 5) * floor((height + 3) / 4) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_5x5_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_5x5_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 4) / 5) * floor((height + 4) / 5) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_6x5_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_6x5_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 5) / 6) * floor((height + 4) / 5) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_6x6_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_6x6_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 5) / 6) * floor((height + 5) / 6) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_8x5_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_8x5_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 7) / 8) * floor((height + 4) / 5) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_8x6_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_8x6_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 7) / 8) * floor((height + 5) / 6) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_8x8_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_8x8_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 7) / 8) * floor((height + 7) / 8) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_10x5_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_10x5_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 9) / 10) * floor((height + 4) / 5) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_10x6_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_10x6_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 9) / 10) * floor((height + 5) / 6) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_10x8_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_10x8_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 9) / 10) * floor((height + 7) / 8) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_10x10_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_10x10_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 9) / 10) * floor((height + 9) / 10) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_12x10_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_12x10_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 11) / 12) * floor((height + 9) / 10) * 16

  If it is not, an INVALID_VALUE error is generated.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGBA_ASTC_12x12_KHR

  COMPRESSED_SRGB8_ALPHA8_ASTC_12x12_KHR

  The byteLength of the ArrayBufferView, pixels, passed to compressedTexImage2D or compressedTexSubImage2D must be equal to the following number of bytes:

  floor((width + 11) / 12) * floor((height + 11) / 12) * 16

  If it is not, an INVALID_VALUE error is generated.

IDL

[Exposed=(Window,Worker), LegacyNoInterfaceObject]
interface WEBGL_compressed_texture_astc {
    /* Compressed Texture Format */
    const GLenum COMPRESSED_RGBA_ASTC_4x4_KHR = 0x93B0;
    const GLenum COMPRESSED_RGBA_ASTC_5x4_KHR = 0x93B1;
    const GLenum COMPRESSED_RGBA_ASTC_5x5_KHR = 0x93B2;
    const GLenum COMPRESSED_RGBA_ASTC_6x5_KHR = 0x93B3;
    const GLenum COMPRESSED_RGBA_ASTC_6x6_KHR = 0x93B4;
    const GLenum COMPRESSED_RGBA_ASTC_8x5_KHR = 0x93B5;
    const GLenum COMPRESSED_RGBA_ASTC_8x6_KHR = 0x93B6;
    const GLenum COMPRESSED_RGBA_ASTC_8x8_KHR = 0x93B7;
    const GLenum COMPRESSED_RGBA_ASTC_10x5_KHR = 0x93B8;
    const GLenum COMPRESSED_RGBA_ASTC_10x6_KHR = 0x93B9;
    const GLenum COMPRESSED_RGBA_ASTC_10x8_KHR = 0x93BA;
    const GLenum COMPRESSED_RGBA_ASTC_10x10_KHR = 0x93BB;
    const GLenum COMPRESSED_RGBA_ASTC_12x10_KHR = 0x93BC;
    const GLenum COMPRESSED_RGBA_ASTC_12x12_KHR = 0x93BD;

    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_4x4_KHR = 0x93D0;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_5x4_KHR = 0x93D1;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_5x5_KHR = 0x93D2;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_6x5_KHR = 0x93D3;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_6x6_KHR = 0x93D4;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_8x5_KHR = 0x93D5;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_8x6_KHR = 0x93D6;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_8x8_KHR = 0x93D7;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_10x5_KHR = 0x93D8;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_10x6_KHR = 0x93D9;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_10x8_KHR = 0x93DA;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_10x10_KHR = 0x93DB;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_12x10_KHR = 0x93DC;
    const GLenum COMPRESSED_SRGB8_ALPHA8_ASTC_12x12_KHR = 0x93DD;

    // Profile query support.
    sequence<DOMString> getSupportedProfiles();
};
  

New Functions

sequence<DOMString> getSupportedProfiles()

Returns the names of the ASTC profiles supported by the implementation. As of this writing, valid return values will include "ldr", corresponding to the GL_KHR_texture_compression_astc_ldr extension string; and "hdr", corresponding to the GL_KHR_texture_compression_astc_hdr extension string. More profiles may be added in the future.

The intent of the getSupportedProfiles function is to allow easy reconstruction of the underlying OpenGL or OpenGL ES extension strings for environments like Emscripten, by prepending the string GL_KHR_texture_compression_astc_ to the returned profile names.

New Tokens

compressedTexImage2D(GLenum internalformat)

Accepted by the internalformat parameter: COMPRESSED_RGBA_ASTC_4x4_KHR, COMPRESSED_RGBA_ASTC_5x4_KHR, COMPRESSED_RGBA_ASTC_5x5_KHR, COMPRESSED_RGBA_ASTC_6x5_KHR, COMPRESSED_RGBA_ASTC_6x6_KHR, COMPRESSED_RGBA_ASTC_8x5_KHR, COMPRESSED_RGBA_ASTC_8x6_KHR, COMPRESSED_RGBA_ASTC_8x8_KHR, COMPRESSED_RGBA_ASTC_10x5_KHR, COMPRESSED_RGBA_ASTC_10x6_KHR, COMPRESSED_RGBA_ASTC_10x8_KHR, COMPRESSED_RGBA_ASTC_10x10_KHR, COMPRESSED_RGBA_ASTC_12x10_KHR, COMPRESSED_RGBA_ASTC_12x12_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_4x4_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_5x4_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_5x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_6x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_6x6_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_8x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_8x6_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_8x8_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x6_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x8_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x10_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_12x10_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_12x12_KHR

compressedTexSubImage2D(GLenum internalformat)

Accepted by the internalformat parameter: COMPRESSED_RGBA_ASTC_4x4_KHR, COMPRESSED_RGBA_ASTC_5x4_KHR, COMPRESSED_RGBA_ASTC_5x5_KHR, COMPRESSED_RGBA_ASTC_6x5_KHR, COMPRESSED_RGBA_ASTC_6x6_KHR, COMPRESSED_RGBA_ASTC_8x5_KHR, COMPRESSED_RGBA_ASTC_8x6_KHR, COMPRESSED_RGBA_ASTC_8x8_KHR, COMPRESSED_RGBA_ASTC_10x5_KHR, COMPRESSED_RGBA_ASTC_10x6_KHR, COMPRESSED_RGBA_ASTC_10x8_KHR, COMPRESSED_RGBA_ASTC_10x10_KHR, COMPRESSED_RGBA_ASTC_12x10_KHR, COMPRESSED_RGBA_ASTC_12x12_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_4x4_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_5x4_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_5x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_6x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_6x6_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_8x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_8x6_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_8x8_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x5_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x6_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x8_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_10x10_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_12x10_KHR, COMPRESSED_SRGB8_ALPHA8_ASTC_12x12_KHR

Errors

Revision History

Revision 1, 2015/03/10

• Initial revision.

Revision 2, 2015/08/07

• Added profile string support. Renamed constants back to _KHR.

Revision 3, 2015/08/10

• Clarified intent of getSupportedProfiles. Stressed that OpenGL ES extension defines the behavior.

Revision 4, 2015/08/10

• Moved to draft status.

Revision 5, 2016/12/12

• Moved to community approved after discussion on public_webgl list.