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'''OpenGL extension ARB.texture_compression
This module customises the behaviour of the
OpenGL.raw.GL.ARB.texture_compression to provide a more
Python-friendly API
Overview (from the spec)
Compressing texture images can reduce texture memory utilization and
improve performance when rendering textured primitives. This extension
allows OpenGL applications to use compressed texture images by providing:
(1) A framework upon which extensions providing specific compressed
image formats can be built.
(2) A set of generic compressed internal formats that allow
applications to specify that texture images should be stored in
compressed form without needing to code for specific compression
formats.
An application can define compressed texture images by providing a texture
image stored in a specific compressed image format. This extension does
not define any specific compressed image formats, but it does provide the
mechanisms necessary to enable other extensions that do.
An application can also define compressed texture images by providing an
uncompressed texture image but specifying a compressed internal format.
In this case, the GL will automatically compress the texture image using
the appropriate image format. Compressed internal formats can either be
specific (as above) or generic. Generic compressed internal formats are
not actual image formats, but are instead mapped into one of the specific
compressed formats provided by the GL (or to an uncompressed base internal
format if no appropriate compressed format is available). Generic
compressed internal formats allow applications to use texture compression
without needing to code to any particular compression algorithm. Generic
compressed formats allow the use of texture compression across a wide
range of platforms with differing compression algorithms and also allow
future GL implementations to substitute improved compression methods
transparently.
Compressed texture images can be obtained from the GL in uncompressed form
by calling GetTexImage and in compressed form by calling
GetCompressedTexImageARB. Queried compressed images can be saved and
later reused by calling CompressedTexImage[123]DARB. Pre-compressed
texture images do not need to be processed by the GL and should
significantly improve texture loading performance relative to uncompressed
images.
This extension does not define specific compressed image formats (e.g.,
S3TC, FXT1), nor does it provide means to encode or decode such images.
To support images in a specific compressed format, a hardware vendor
would:
(1) Provide a new extension defininig specific compressed
<internalformat> and <format> tokens for TexImage[123]D,
TexSubImage[123]D, CopyTexImage[12]D, CompressedTexImage[123]DARB,
CompressedTexSubImage[123]DARB, and GetCompressedTexImageARB calls.
(2) Specify the encoding of compressed images of that specific format.
(3) Specify a method for deriving the size of compressed images of that
specific format, using the <internalformat>, <width>, <height>,
<depth> parameters, and (if necessary) the compressed image itself.
The official definition of this extension is available here:
http://www.opengl.org/registry/specs/ARB/texture_compression.txt
'''
from OpenGL import platform, constants, constant, arrays
from OpenGL import extensions, wrapper
from OpenGL.GL import glget
import ctypes
from OpenGL.raw.GL.ARB.texture_compression import *
### END AUTOGENERATED SECTION
from OpenGL.GL import images
for dimensions in (1,2,3):
for function in ('glCompressedTexImage%sDARB','glCompressedTexSubImage%sDARB'):
name = function%(dimensions,)
globals()[ name ] = images.compressedImageFunction(
globals()[ name ]
)
del name, function
del dimensions
if glGetCompressedTexImageARB:
def glGetCompressedTexImageARB( target, level, img=None ):
"""Retrieve a compressed texture image"""
if img is None:
length = glget.glGetTexLevelParameteriv(
target, 0,
GL_TEXTURE_COMPRESSED_IMAGE_SIZE_ARB,
)
img = arrays.ArrayDataType.zeros( (length,), constants.GL_UNSIGNED_BYTE )
return glGetCompressedTexImageARB(target, 0, img);
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