WebGL WEBGL_compressed_texture_pvrtc Extension Specification

Name

WEBGL_compressed_texture_pvrtc

Contact

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

Contributors

Members of the WebGL working group

Version

Last modified date: March 28, 2022
Revision: 5

Number

WebGL extension #13

Dependencies

Written against the WebGL API 1.0 specification.

Overview

Note: this extension is deprecated. On systems that support this compressed texture format, please consider using the WEBGL_compressed_texture_etc or WEBGL_compressed_texture_astc formats instead. They are more widely supported and offer a larger range of quality controls.

This extension exposes the compressed texture formats defined in the IMG_texture_compression_pvrtc OpenGL extension to WebGL.

When this extension is enabled:

• Compression formats COMPRESSED_RGB_PVRTC_4BPPV1_IMG, COMPRESSED_RGB_PVRTC_2BPPV1_IMG, COMPRESSED_RGBA_PVRTC_4BPPV1_IMG, and COMPRESSED_RGBA_PVRTC_2BPPV1_IMG may be passed to the compressedTexImage2D and compressedTexSubImage2D entry points.
• Calling getParameter with the argument COMPRESSED_TEXTURE_FORMATS will include the 4 formats from this specification.

• The following format-specific restrictions apply to all of the formats described by this extension:

  In compressedTexImage2D, the width and height parameters must be powers of two. Otherwise, an INVALID_VALUE error is generated.

  In compressedTexSubImage2D, the width and height parameters must be equal to the current values of the existing texture image, and the xoffset and yoffset parameters must be zero. Otherwise, an INVALID_VALUE error is generated.

• The following format-specific restrictions must also be enforced:

  COMPRESSED_RGB_PVRTC_4BPPV1_IMG

  COMPRESSED_RGBA_PVRTC_4BPPV1_IMG

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

  max(width, 8) * max(height, 8) / 2

  If it is not, an INVALID_VALUE error is generated.

  COMPRESSED_RGB_PVRTC_2BPPV1_IMG

  COMPRESSED_RGBA_PVRTC_2BPPV1_IMG

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

  max(width, 16) * max(height, 8) / 4

  If it is not, an INVALID_VALUE error is generated.

IDL

[Exposed=(Window,Worker), LegacyNoInterfaceObject]
interface WEBGL_compressed_texture_pvrtc {
    /* Compressed Texture Formats */
    const GLenum COMPRESSED_RGB_PVRTC_4BPPV1_IMG      = 0x8C00;
    const GLenum COMPRESSED_RGB_PVRTC_2BPPV1_IMG      = 0x8C01;
    const GLenum COMPRESSED_RGBA_PVRTC_4BPPV1_IMG     = 0x8C02;
    const GLenum COMPRESSED_RGBA_PVRTC_2BPPV1_IMG     = 0x8C03;
};
  

Revision History

Revision 1, 2012/08/07

• Initial revision.

Revision 2, 2013/07/03

• Clarified that length of ArrayBufferView is actually byteLength.

Revision 3, 2014/06/27

• Moved to community approved after discussion on public_webgl list.

Revision 4, 2014/07/15

• Added NoInterfaceObject extended attribute.

Revision 5, 2022/03/28

• Added deprecation note and recommended ETC or ASTC formats instead.