The WEBGL_compressed_texture_pvrtc extension is part of the WebGL API and exposes four PVRTC 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.
Note: PVRTC is typically only available on mobile devices with PowerVR chipsets. It is used in all generations of the iPhone, iPod Touch and iPad and supported on certain Android devices that use a PowerVR GPU.
This extension is available to both, WebGL1 and WebGL2 contexts.
Note: On iOS devices, this extension is named WEBKIT_WEBGL_compressed_texture_pvrtc.
The compressed texture formats are exposed by four constants and can be used in two functions: compressedTexImage2D() (where the height and width parameters must be powers of 2) and compressedTexSubImage2D() (where the height and width parameters must equal the current values of the existing texture and the xoffset and yoffset parameters must be 0).
ext.COMPRESSED_RGB_PVRTC_4BPPV1_IMG-
RGB compression in 4-bit mode. One block for each 4×4 pixels.
ext.COMPRESSED_RGBA_PVRTC_4BPPV1_IMG-
RGBA compression in 4-bit mode. One block for each 4×4 pixels.
ext.COMPRESSED_RGB_PVRTC_2BPPV1_IMG-
RGB compression in 2-bit mode. One block for each 8×4 pixels.
ext.COMPRESSED_RGBA_PVRTC_2BPPV1_IMG-
RGBA compression in 2-bit mode. One block for each 8×4 pixels.
const ext = gl.getExtension("WEBGL_compressed_texture_pvrtc");
const texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.compressedTexImage2D(
gl.TEXTURE_2D,
0,
ext.COMPRESSED_RGB_PVRTC_4BPPV1_IMG,
512,
512,
0,
textureData,
);