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.

       GL_STENCIL_INDEX is accepted for format only if the GL version is 4.4 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 log 2 ⁡ max, where max is the
       returned value of GL_MAX_TEXTURE_SIZE.

       GL_INVALID_OPERATION is generated 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 generated 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 format is GL_STENCIL_INDEX and the base internal
       format is not GL_STENCIL_INDEX or GL_DEPTH_STENCIL.

       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 © 2010-2013 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