WebGL WEBGL_compressed_texture_etc1 Extension Specification

Name

WEBGL_compressed_texture_etc1

Contact

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

Contributors

Members of the WebGL working group

Version

Last modified date: July 15, 2014
Revision: 7

Number

WebGL extension #24

Dependencies

Written against the WebGL API 1.0 specification.

Overview

This extension exposes the compressed texture format defined in the OES_compressed_ETC1_RGB8_texture OpenGL ES extension to WebGL.

When this extension is enabled:

• Compression format COMPRESSED_RGB_ETC1_WEBGL may be passed to the compressedTexImage2D entry point. This format correspond to the format defined in the OES_compressed_ETC1_RGB8_texture OpenGL ES extension. Although the enum name is changed, the numeric value is the same. The correspondence is given by this table:

  WebGL format enum	OpenGL format enum	Numeric value
  COMPRESSED_RGB_ETC1_WEBGL	ETC1_RGB8_OES	0x8D64

• Calling getParameter with the argument COMPRESSED_TEXTURE_FORMATS will include the format from this specification.

• The following format-specific restrictions must be enforced:

  COMPRESSED_RGB_ETC1_WEBGL

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

  floor((width + 3) / 4) * floor((height + 3) / 4) * 8

  If it is not, an INVALID_VALUE error is generated.

IDL

[Exposed=(Window,Worker), LegacyNoInterfaceObject]
interface WEBGL_compressed_texture_etc1 {
    /* Compressed Texture Format */
    const GLenum COMPRESSED_RGB_ETC1_WEBGL = 0x8D64; 
};
  

Revision History

Revision 1, 2012/02/23

• Initial revision.

Revision 2, 2013/07/03

• Clarified that length of ArrayBufferView is actually byteLength.

Revision 3, 2013/11/27

• Moved to draft status.

Revision 4, 2013/12/03

• Assigned extension number 24 to WEBGL_compressed_texture_etc1 extension.

Revision 5, 2014/03/07

• Remove ability to use the format with compressedTexSubImage2D, as per the GLES extension spec.

Revision 6, 2014/06/27

• Moved to community approved after discussion on public_webgl list.

Revision 7, 2014/07/15

• Added NoInterfaceObject extended attribute.