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