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GLCOMPRESSEDTEXIMAGE(3G)	 OpenGL Manual	      GLCOMPRESSEDTEXIMAGE(3G)

NAME
       glCompressedTexImage2D - specify a two-dimensional texture image in a
       compressed format

C SPECIFICATION
       void glCompressedTexImage2D(GLenum target, GLint level,
				   GLenum internalformat, GLsizei width,
				   GLsizei height, GLint border,
				   GLsizei imageSize, const GLvoid * data);

PARAMETERS
       target
	   Specifies the target texture. Must be GL_TEXTURE_2D,
	   GL_PROXY_TEXTURE_2D, GL_TEXTURE_1D_ARRAY,
	   GL_PROXY_TEXTURE_1D_ARRAY, GL_TEXTURE_CUBE_MAP_POSITIVE_X,
	   GL_TEXTURE_CUBE_MAP_NEGATIVE_X, GL_TEXTURE_CUBE_MAP_POSITIVE_Y,
	   GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, GL_TEXTURE_CUBE_MAP_POSITIVE_Z,
	   GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, or GL_PROXY_TEXTURE_CUBE_MAP.

       level
	   Specifies the level-of-detail number. Level 0 is the base image
	   level. Level n is the nth mipmap reduction image.

       internalformat
	   Specifies the format of the compressed image data stored at address
	   data.

       width
	   Specifies the width of the texture image. All implementations
	   support 2D texture and cube map texture images that are at least
	   16384 texels wide.

       height
	   Specifies the height of the texture image. All implementations
	   support 2D texture and cube map texture images that are at least
	   16384 texels high.

       border
	   This value must be 0.

       imageSize
	   Specifies the number of unsigned bytes of image data starting at
	   the address specified by data.

       data
	   Specifies a pointer to the compressed image data in memory.

DESCRIPTION
       Texturing allows elements of an image array to be read by shaders.

       glCompressedTexImage2D loads a previously defined, and retrieved,
       compressed two-dimensional texture image if target is GL_TEXTURE_2D, or
       one of the cube map faces such as GL_TEXTURE_CUBE_MAP_POSITIVE_X. (see
       glTexImage2D()).

       If target is GL_TEXTURE_1D_ARRAY, data is treated as an array of
       compressed 1D textures.

       If target is GL_PROXY_TEXTURE_2D, GL_PROXY_TEXTURE_1D_ARRAY or
       GL_PROXY_CUBE_MAP, no data is read from data, but all of the texture
       image state is recalculated, checked for consistency, and checked
       against the implementation's capabilities. If the implementation cannot
       handle a texture of the requested texture size, it sets all of the
       image state to 0, but does not generate an error (see glGetError()). To
       query for an entire mipmap array, use an image array level greater than
       or equal to 1.

       internalformat must be a known compressed image format (such as
       GL_RGTC) or an extension-specified compressed-texture format. When a
       texture is loaded with glTexImage2D() using a generic compressed
       texture format (e.g., GL_COMPRESSED_RGB), the GL selects from one of
       its extensions supporting compressed textures. In order to load the
       compressed texture image using glCompressedTexImage2D, query the
       compressed texture image's size and format using
       glGetTexLevelParameter().

       If a non-zero named buffer object is bound to the
       GL_PIXEL_UNPACK_BUFFER target (see glBindBuffer()) while a texture
       image is specified, data is treated as a byte offset into the buffer
       object's data store.

       If the compressed data are arranged into fixed-size blocks of texels,
       the pixel storage modes can be used to select a sub-rectangle from a
       larger containing rectangle. These pixel storage modes operate in the
       same way as they do for glTexImage2D(). In the following description,
       denote by bs, bw, bh, and bd, the values of pixel storage modes
       GL_UNPACK_COMPRESSED_BLOCK_SIZE, GL_UNPACK_COMPRESSED_BLOCK_WIDTH,
       GL_UNPACK_COMPRESSED_BLOCK_HEIGHT, and
       GL_UNPACK_COMPRESSED_BLOCK_DEPTH, respectively.	bs is the compressed
       block size in bytes; bw, bh, and bd are the compressed block width,
       height, and depth in pixels.

       By default the pixel storage modes GL_UNPACK_ROW_LENGTH,
       GL_UNPACK_SKIP_ROWS, GL_UNPACK_SKIP_PIXELS, GL_UNPACK_IMAGE_HEIGHT and
       GL_UNPACK_SKIP_IMAGES are ignored for compressed images. To enable
       GL_UNPACK_SKIP_PIXELS and GL_UNPACK_ROW_LENGTH, bs and bw must both be
       non-zero. To also enable GL_UNPACK_SKIP_ROWS and
       GL_UNPACK_IMAGE_HEIGHT, bh must be non-zero. To also enable
       GL_UNPACK_SKIP_IMAGES, bd must be non-zero. All parameters must be
       consistent with the compressed format to produce the desired results.

       When selecting a sub-rectangle from a compressed image:

       ·   the value of GL_UNPACK_SKIP_PIXELS must be a multiple of bw;.RE

	   ·   the value of GL_UNPACK_SKIP_ROWS must be a multiple of bw..RE

	       imageSize must be equal to:

	       b s × width b w × height b h

NOTES
       The specific compressed internal formats GL_COMPRESSED_RGB8_ETC2,
       GL_COMPRESSED_SRGB8_ETC2, GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2,
       GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2,
       GL_COMPRESSED_RGBA8_ETC2_EAC, GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC,
       GL_COMPRESSED_R11_EAC, GL_COMPRESSED_SIGNED_R11_EAC,
       GL_COMPRESSED_RG11_EAC, and GL_COMPRESSED_SIGNED_RG11_EAC are available
       only if the GL version is 4.3 or higher.

ERRORS
       GL_INVALID_ENUM is generated if internalformat is not one of the
       specific compressed internal formats: GL_COMPRESSED_RED_RGTC1,
       GL_COMPRESSED_SIGNED_RED_RGTC1, GL_COMPRESSED_RG_RGTC2,
       GL_COMPRESSED_SIGNED_RG_RGTC2.  GL_COMPRESSED_RGBA_BPTC_UNORM,
       GL_COMPRESSED_SRGB_ALPHA_BPTC_UNORM,
       GL_COMPRESSED_RGB_BPTC_SIGNED_FLOAT,
       GL_COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT, GL_COMPRESSED_RGB8_ETC2,
       GL_COMPRESSED_SRGB8_ETC2, GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2,
       GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2,
       GL_COMPRESSED_RGBA8_ETC2_EAC, GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC,
       GL_COMPRESSED_R11_EAC, GL_COMPRESSED_SIGNED_R11_EAC,
       GL_COMPRESSED_RG11_EAC, or GL_COMPRESSED_SIGNED_RG11_EAC.

       GL_INVALID_VALUE is generated if imageSize is not consistent with the
       format, dimensions, and contents of the specified compressed image
       data.

       GL_INVALID_VALUE is generated if border is not 0.

       GL_INVALID_OPERATION is generated if parameter combinations are not
       supported by the specific compressed internal format as specified in
       the specific texture compression extension.

       GL_INVALID_OPERATION is generated if a non-zero buffer object name is
       bound to the GL_PIXEL_UNPACK_BUFFER target and the buffer object's data
       store is currently mapped.

       GL_INVALID_OPERATION is generated if a non-zero buffer object name is
       bound to the GL_PIXEL_UNPACK_BUFFER target and the data would be
       unpacked from the buffer object such that the memory reads required
       would exceed the data store size.

       Undefined results, including abnormal program termination, are
       generated if data is not encoded in a manner consistent with the
       extension specification defining the internal compression format.

ASSOCIATED GETS
       glGetCompressedTexImage()

       glGet() with argument GL_TEXTURE_COMPRESSED

       glGet() with argument GL_PIXEL_UNPACK_BUFFER_BINDING

       glGetTexLevelParameter() with arguments GL_TEXTURE_INTERNAL_FORMAT and
       GL_TEXTURE_COMPRESSED_IMAGE_SIZE

SEE ALSO
       glActiveTexture(), glCompressedTexImage1D(), glCompressedTexImage3D(),
       glCompressedTexSubImage1D(), glCompressedTexSubImage2D(),
       glCompressedTexSubImage3D(), glCopyTexImage1D(), glCopyTexSubImage1D(),
       glCopyTexSubImage2D(), glCopyTexSubImage3D(), glPixelStore(),
       glTexImage2D(), glTexImage3D(), glTexSubImage1D(), glTexSubImage2D(),
       glTexSubImage3D(), glTexParameter()

COPYRIGHT
       Copyright © 1991-2006 Silicon Graphics, Inc.  © 2011 Khronos Group.
       This document is licensed under the SGI Free Software B License. For
       details, see http://oss.sgi.com/projects/FreeB/.

AUTHORS
       opengl.org

opengl.org			  03/16/2013	      GLCOMPRESSEDTEXIMAGE(3G)
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