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GLGETTEXIMAGE(3G)					     GLGETTEXIMAGE(3G)

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,
	       GL_TEXTURE_2D, and GL_TEXTURE_3D	 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  for the returned data.  The  supported  for‐
	       mats  are  GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_BGR,
	       GL_RGBA, GL_BGRA, 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,	     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, and GL_UNSIGNED_INT_2_10_10_10_REV.

       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),	 glTexImage2D	(GL_TEXTURE_2D),  or  glTexImage3D  (‐
       GL_TEXTURE_3D).	level specifies	 the  level-of-detail  number  of  the
       desired	image.	 format	 and type specify the  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 parame‐
       ters, 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,  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
       (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	compo‐
       nent 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.

       When  the  GL_ARB_multitexture  extension  is  supported, glGetTexImage
       returns the texture image for the active texture unit.

       The    types    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,  and  the
       formats GL_BGR, and GL_BGRA are available only if the GL version is 1.2
       or greater.

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  log2(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.

       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, or GL_UNSIGNED_SHORT_5_6_5_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, or GL_UNSIGNED_INT_2_10_10_10_REV, and for‐
       mat is neither GL_RGBA or GL_BGRA.

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_INTERNALFORMAT
       glGet with arguments GL_PACK_ALIGNMENT and others

SEE ALSO
       glActiveTextureARB,  glDrawPixels,  glReadPixels,  glTexEnv,  glTexGen,
       glTexImage1D,	  glTexImage2D,	    glTexImage3D,     glTexSubImage1D,
       glTexSubImage2D, glTexSubImage3D, glTexParameter

							     GLGETTEXIMAGE(3G)
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