NAME
	  glGetTexImage	- return a texture image


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


     PARAMETERS
	  target  Specifies which texture is to	be obtained.
		  GL_TEXTURE_1D	and GL_TEXTURE_2D 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_RED,	GL_GREEN, GL_BLUE,
		  GL_ALPHA, GL_RGB, GL_RGBA, GL_LUMINANCE, and
		  GL_LUMINANCE_ALPHA.

	  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, and GL_FLOAT.

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

     DESCRIPTION
	  glGetTexImage	returns	a texture image	into pixels.  target
	  specifies whether the	desired	texture	image is one specified
	  by glTexImage1D (GL_TEXTURE_1D) or by	glTexImage2D
	  (GL_TEXTURE_2D).  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
	  pages	glTexImage1D and glDrawPixels for a description	of the
	  acceptable values for	the format and type parameters,
	  respectively.

	  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
	  called with the same format and type,	with x and y set to 0,
	  width	set to the width of the	texture	image (including
	  border if one	was specified),	and height set to 1 for	1D
	  images, or to	the height of the texture image	(including
	  border if one	was specified) for 2D images.  Because the
	  internal texture image is an RGBA image, pixel formats
	  GL_COLOR_INDEX, GL_STENCIL_INDEX, and	GL_DEPTH_COMPONENT are
	  not accepted,	and pixel type GL_BITMAP is not	accepted.

	  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 pixels, 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 pixels.

     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 max, where max is	the returned value of
	  GL_MAX_TEXTURE_SIZE.

	  GL_INVALID_OPERATION is generated if glGetTexImage is
	  executed between the execution of glBegin and	the
	  corresponding	execution of glEnd.

     ASSOCIATED	GETS
	  glGetTexLevelParameter with argument GL_TEXTURE_WIDTH
	  glGetTexLevelParameter with argument GL_TEXTURE_HEIGHT
	  glGetTexLevelParameter with argument GL_TEXTURE_BORDER
	  glGetTexLevelParameter with argument GL_TEXTURE_COMPONENTS
	  glGet	with arguments GL_PACK_ALIGNMENT and others

     SEE ALSO
	  glDrawPixels,	glReadPixels, glTexEnv,	glTexGen,
	  glTexImage1D,	glTexImage2D, glTexSubImage1D,
	  glTexSubImage2D, glTexParameter