glGetTexImage — return a texture image
void glGetTexImage( | GLenum | target, |
GLint | level, | |
GLenum | format, | |
GLenum | type, | |
GLvoid * | img) ; |
target
Specifies which texture is to be obtained.
GL_TEXTURE_1D
, GL_TEXTURE_2D
, GL_TEXTURE_3D
,
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
format
Specifies a pixel format for the returned data.
The supported formats 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
.
img
Returns the texture image.
Should be a pointer to an array of the type specified by type
.
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_2D
or any of
GL_TEXTURE_CUBE_MAP_*
),
or
glTexImage3D (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 pages glTexImage1D and glDrawPixels
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
(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 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
.
If an error is generated,
no change is made to the contents of img
.
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.
For OpenGL versions 1.3 and greater, or when the ARB_multitexture
extension is supported, glGetTexImage
returns
the texture image for the active texture unit.
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
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
, 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 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
.
GL_INVALID_OPERATION
is generated if glGetTexImage
is executed between the execution of glBegin
and the corresponding execution of glEnd.
glGetTexLevelParameter with argument GL_TEXTURE_WIDTH
glGetTexLevelParameter with argument GL_TEXTURE_HEIGHT
glGetTexLevelParameter with argument GL_TEXTURE_BORDER
glGetTexLevelParameter with argument GL_TEXTURE_INTERNAL_FORMAT
glGet with arguments GL_PACK_ALIGNMENT
and others
glGet with argument GL_PIXEL_PACK_BUFFER_BINDING
glActiveTexture, glDrawPixels, glReadPixels, glTexEnv, glTexGen, glTexImage1D, glTexImage2D, glTexImage3D, glTexSubImage1D, glTexSubImage2D, glTexSubImage3D, glTexParameter
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.