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GLGETTEXIMAGE(3G)		 OpenGL Manual		     GLGETTEXIMAGE(3G)

NAME
       glGetTexImage - return a texture image

C SPECIFICATION
       void glGetTexImage(GLenum target, GLint level, GLenum format,
			  GLenum type, GLvoid * img);

PARAMETERS
       target
	   Specifies which texture is to be obtained.  GL_TEXTURE_1D,
	   GL_TEXTURE_2D, GL_TEXTURE_3D, GL_TEXTURE_1D_ARRAY,
	   GL_TEXTURE_2D_ARRAY, GL_TEXTURE_RECTANGLE,
	   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, and GL_TEXTURE_CUBE_MAP_NEGATIVE_Z
	   are accepted.

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

       format
	   Specifies a pixel format for the returned data. The supported
	   formats are GL_STENCIL_INDEX, GL_DEPTH_COMPONENT, GL_DEPTH_STENCIL,
	   GL_RED, GL_GREEN, GL_BLUE, GL_RG, GL_RGB, GL_RGBA, GL_BGR, GL_BGRA,
	   GL_RED_INTEGER, GL_GREEN_INTEGER, GL_BLUE_INTEGER, GL_RG_INTEGER,
	   GL_RGB_INTEGER, GL_RGBA_INTEGER, GL_BGR_INTEGER, GL_BGRA_INTEGER.

       type
	   Specifies a pixel type for the returned data. The supported types
	   are GL_UNSIGNED_BYTE, GL_BYTE, GL_UNSIGNED_SHORT, GL_SHORT,
	   GL_UNSIGNED_INT, GL_INT, GL_HALF_FLOAT, GL_FLOAT,
	   GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV,
	   GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV,
	   GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV,
	   GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV,
	   GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV,
	   GL_UNSIGNED_INT_10_10_10_2, GL_UNSIGNED_INT_2_10_10_10_REV,
	   GL_UNSIGNED_INT_24_8, GL_UNSIGNED_INT_10F_11F_11F_REV,
	   GL_UNSIGNED_INT_5_9_9_9_REV, and GL_FLOAT_32_UNSIGNED_INT_24_8_REV.

       img
	   Returns the texture image. Should be a pointer to an array of the
	   type specified by type.

DESCRIPTION
       glGetTexImage returns a texture image into img.	target specifies
       whether the desired texture image is one specified by glTexImage1D()
       (GL_TEXTURE_1D), glTexImage2D() (GL_TEXTURE_1D_ARRAY,
       GL_TEXTURE_RECTANGLE, GL_TEXTURE_2D or any of GL_TEXTURE_CUBE_MAP_*),
       or glTexImage3D() (GL_TEXTURE_2D_ARRAY, GL_TEXTURE_3D).	level
       specifies the level-of-detail number of the desired image.  format and
       type specify the format and type of the desired image array. See the
       reference page for glTexImage1D() for a description of the acceptable
       values for the format and type parameters, respectively.

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

       To understand the operation of glGetTexImage, consider the selected
       internal four-component texture image to be an RGBA color buffer the
       size of the image. The semantics of glGetTexImage are then identical to
       those of glReadPixels(), with the exception that no pixel transfer
       operations are performed, when called with the same format and type,
       with x and y set to 0, width set to the width of the texture image and
       height set to 1 for 1D images, or to the height of the texture image
       for 2D images.

       If the selected texture image does not contain four components, the
       following mappings are applied. Single-component textures are treated
       as RGBA buffers with red set to the single-component value, green set
       to 0, blue set to 0, and alpha set to 1. Two-component textures are
       treated as RGBA buffers with red set to the value of component zero,
       alpha set to the value of component one, and green and blue set to 0.
       Finally, three-component textures are treated as RGBA buffers with red
       set to component zero, green set to component one, blue set to
       component two, and alpha set to 1.

       To determine the required size of img, use glGetTexLevelParameter() to
       determine the dimensions of the internal texture image, then scale the
       required number of pixels by the storage required for each pixel, based
       on format and type. Be sure to take the pixel storage parameters into
       account, especially GL_PACK_ALIGNMENT.

NOTES
       If an error is generated, no change is made to the contents of img.

       glGetTexImage returns the texture image for the active texture unit.

ERRORS
       GL_INVALID_ENUM is generated if target, format, or type is not an
       accepted value.

       GL_INVALID_VALUE is generated if level is less than 0.

       GL_INVALID_VALUE may be generated if level is greater than log 2 ⁡ max,
       where max is the returned value of GL_MAX_TEXTURE_SIZE.

       GL_INVALID_OPERATION is returned if type is one of
       GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV,
       GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV, or
       GL_UNSIGNED_INT_10F_11F_11F_REV and format is not GL_RGB.

       GL_INVALID_OPERATION is returned if type is one of
       GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV,
       GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV,
       GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV,
       GL_UNSIGNED_INT_10_10_10_2, GL_UNSIGNED_INT_2_10_10_10_REV, or
       GL_UNSIGNED_INT_5_9_9_9_REV and format is neither GL_RGBA or GL_BGRA.

       GL_INVALID_OPERATION is generated if a non-zero buffer object name is
       bound to the GL_PIXEL_PACK_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_PACK_BUFFER target and the data would be packed
       to the buffer object such that the memory writes required would exceed
       the data store size.

       GL_INVALID_OPERATION is generated if a non-zero buffer object name is
       bound to the GL_PIXEL_PACK_BUFFER target and img is not evenly
       divisible into the number of bytes needed to store in memory a datum
       indicated by type.

ASSOCIATED GETS
       glGetTexLevelParameter() with argument GL_TEXTURE_WIDTH

       glGetTexLevelParameter() with argument GL_TEXTURE_HEIGHT

       glGetTexLevelParameter() with argument GL_TEXTURE_INTERNAL_FORMAT

       glGet() with arguments GL_PACK_ALIGNMENT and others

       glGet() with argument GL_PIXEL_PACK_BUFFER_BINDING

SEE ALSO
       glActiveTexture(), glReadPixels(), glTexImage1D(), glTexImage2D(),
       glTexImage3D(), glTexSubImage1D(), glTexSubImage2D(),
       glTexSubImage3D(), glTexParameter()

COPYRIGHT
       Copyright © 1991-2006 Silicon Graphics, Inc. Copyright © 2010 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		     GLGETTEXIMAGE(3G)
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