WEBGL_compressed_texture_etc - Web APIs 编辑

The WEBGL_compressed_texture_etc extension is part of the WebGL API and exposes 10 ETC/EAC compressed texture formats.

Compressed textures reduce the amount of memory needed to store a texture on the GPU, allowing for higher resolution textures or more of the same resolution textures.

WebGL extensions are available using the WebGLRenderingContext.getExtension() method. For more information, see also Using Extensions in the WebGL tutorial.

Availability: This extension is available to both, WebGL1 and WebGL2 contexts.

Constants

The compressed texture formats are exposed by 10 constants and can be used in two functions: compressedTexImage2D() and compressedTexSubImage2D().

ext.COMPRESSED_R11_EAC

One-channel (red) unsigned format compression.

ext.COMPRESSED_SIGNED_R11_EAC

One-channel (red) signed format compression.

ext.COMPRESSED_RG11_EAC

Two-channel (red and green) unsigned format compression.

ext.COMPRESSED_SIGNED_RG11_EAC

Two-channel (red and green) signed format compression.

ext.COMPRESSED_RGB8_ETC2

Compresses RGB8 data with no alpha channel.

ext.COMPRESSED_RGBA8_ETC2_EAC

Compresses RGBA8 data. The RGB part is encoded the same as RGB_ETC2, but the alpha part is encoded separately.

ext.COMPRESSED_SRGB8_ETC2

Compresses sRGB8 data with no alpha channel.

ext.COMPRESSED_SRGB8_ALPHA8_ETC2_EAC

Compresses sRGBA8 data. The sRGB part is encoded the same as SRGB_ETC2, but the alpha part is encoded separately.

ext.COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2

Similar to RGB8_ETC, but with ability to punch through the alpha channel, which means to make it completely opaque or transparent.

ext.COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2

Similar to SRGB8_ETC, but with ability to punch through the alpha channel, which means to make it completely opaque or transparent.

Examples

var ext = gl.getExtension('WEBGL_compressed_texture_etc');

var texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);

gl.compressedTexImage2D(gl.TEXTURE_2D, 0, ext.COMPRESSED_RGBA8_ETC2_EAC, 512, 512, 0, textureData);

Specifications

Browser compatibility

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The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Compatibility notes

• This extension was named WEBGL_compressed_texture_es3 from Firefox 46 to Firefox 51 and used to be available on the WebGL 2 context by default – this is not the case anymore. You have to enable it on both, WebGL 1 and WebGL 2 contexts, in order to use it.

See also

• Ericsson Texture Compression – Wikipedia
• WEBGL_compressed_texture_etc1 (ETC1)
• WebGLRenderingContext.getExtension()
• WebGLRenderingContext.compressedTexImage2D()
• WebGLRenderingContext.compressedTexSubImage2D()
• WebGLRenderingContext.getParameter()