WEBGL_compressed_texture_s3tc extension

The WEBGL_compressed_texture_s3tc extension is part of the WebGL API and exposes four S3TC 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 getExtension() method. For more information, see also Using Extensions in the WebGL tutorial.

[!NOTE] This extension is available to both, WebGL1 and WebGL2 contexts.

Constants

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

• ext.COMPRESSED_RGB_S3TC_DXT1_EXT
  • : A DXT1-compressed image in an RGB image format.
• ext.COMPRESSED_RGBA_S3TC_DXT1_EXT
  • : A DXT1-compressed image in an RGB image format with an on/off alpha value.
• ext.COMPRESSED_RGBA_S3TC_DXT3_EXT
  • : A DXT3-compressed image in an RGBA image format. Compared to a 32-bit RGBA texture, it offers 4:1 compression.
• ext.COMPRESSED_RGBA_S3TC_DXT5_EXT
  • : A DXT5-compressed image in an RGBA image format. It also provides a 4:1 compression, but differs to the DXT3 compression in how the alpha compression is done.

Examples

const ext =
  gl.getExtension("WEBGL_compressed_texture_s3tc") ||
  gl.getExtension("MOZ_WEBGL_compressed_texture_s3tc") ||
  gl.getExtension("WEBKIT_WEBGL_compressed_texture_s3tc");

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

gl.compressedTexImage2D(
  gl.TEXTURE_2D,
  0,
  ext.COMPRESSED_RGBA_S3TC_DXT5_EXT,
  512,
  512,
  0,
  textureData,
);

gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);

Specifications

Browser compatibility

See also

• S3 Texture Compression – OpenGL wiki
• getExtension()
• compressedTexImage2D()
• compressedTexSubImage2D()
• getParameter()