Provided by: opengl-4-man-doc_1.0~svn33624-1_all 
NAME
glGetTexImage, glGetnTexImage, glGetTextureImage - return a texture image
C SPECIFICATION
void glGetTexImage(GLenum target, GLint level, GLenum format, GLenum type,
GLvoid * pixels);
void glGetnTexImage(GLenum target, GLint level, GLenum format, GLenum type,
GLsizei bufSize, void *pixels);
void glGetTextureImage(GLuint texture, GLint level, GLenum format, GLenum type,
GLsizei bufSize, void *pixels);
PARAMETERS
target
Specifies the target to which the texture is bound for glGetTexImage and
glGetnTexImage functions. 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, GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, and
GL_TEXTURE_CUBE_MAP_ARRAY are acceptable.
texture
Specifies the texture object name.
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.
bufSize
Specifies the size of the buffer pixels for glGetnTexImage and glGetTextureImage
functions.
pixels
Returns the texture image. Should be a pointer to an array of the type specified by
type.
DESCRIPTION
glGetTexImage, glGetnTexImage and glGetTextureImage functions return a texture image into
pixels. For glGetTexImage and glGetnTexImage, 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,
GL_TEXTURE_CUBE_MAP_ARRAY). For glGetTextureImage, texture specifies the texture object
name. In addition to types of textures accepted by glGetTexImage and glGetnTexImage, the
function also accepts cube map texture objects (with effective target
GL_TEXTURE_CUBE_MAP). 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. For glGetnTexImage and glGetTextureImage functions, bufSize
tells the size of the buffer to receive the retrieved pixel data. glGetnTexImage and
glGetTextureImage do not write more than bufSize bytes into pixels.
If a non-zero named buffer object is bound to the GL_PIXEL_PACK_BUFFER target (see
glBindBuffer()) while a texture image is requested, pixels 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 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.
If glGetTextureImage is used against a cube map texture object, the texture is treated as
a three-dimensional image of a depth of 6, where the cube map faces are ordered as image
layers, in an order presented in the table below:
┌─────────────┬────────────────────────────────┐
│Layer number │ Cube Map Face │
├─────────────┼────────────────────────────────┤
│0 │ GL_TEXTURE_CUBE_MAP_POSITIVE_X │
├─────────────┼────────────────────────────────┤
│1 │ GL_TEXTURE_CUBE_MAP_NEGATIVE_X │
├─────────────┼────────────────────────────────┤
│2 │ GL_TEXTURE_CUBE_MAP_POSITIVE_Y │
├─────────────┼────────────────────────────────┤
│3 │ GL_TEXTURE_CUBE_MAP_NEGATIVE_Y │
├─────────────┼────────────────────────────────┤
│4 │ GL_TEXTURE_CUBE_MAP_POSITIVE_Z │
├─────────────┼────────────────────────────────┤
│5 │ GL_TEXTURE_CUBE_MAP_NEGATIVE_Z │
└─────────────┴────────────────────────────────┘
NOTES
If an error is generated, no change is made to the contents of pixels.
glGetTexImage and glGetnTexImage return 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 by glGetTexImage and glGetnTexImage functions if target is
not an accepted value. These include:
• GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D, GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D_ARRAY,
GL_TEXTURE_CUBE_MAP_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 for glGetTexImage and glGetnTexImage functions.
• GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D, GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D_ARRAY,
GL_TEXTURE_CUBE_MAP_ARRAY, GL_TEXTURE_RECTANGLE, and GL_TEXTURE_CUBE_MAP for
glGetTextureImage function.
GL_INVALID_OPERATION is generated by glGetTextureImage if texture is not the name of an
existing texture object.
GL_INVALID_ENUM is generated if 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_VALUE is generated if level is non-zero and the effective target is
GL_TEXTURE_RECTANGLE.
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 pixels is not evenly divisible into the number of bytes
needed to store in memory a datum indicated by type.
GL_INVALID_OPERATION is generated by glGetTextureImage and glGetnTexImage if the buffer
size required to store the requested data is greater than bufSize.
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
VERSION SUPPORT
┌──────────────────┬───────────────────────────────────────────────────────────────────────┐
│ │ OpenGL Version │
├──────────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
│Function │ 2.0 │ 2.1 │ 3.0 │ 3.1 │ 3.2 │ 3.3 │ 4.0 │ 4.1 │ 4.2 │ 4.3 │ 4.4 │ 4.5 │
│/ │ │ │ │ │ │ │ │ │ │ │ │ │
│Feature │ │ │ │ │ │ │ │ │ │ │ │ │
│Name │ │ │ │ │ │ │ │ │ │ │ │ │
├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glGetTexImage │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │
├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glGetTextureImage │ - │ - │ - │ - │ - │ - │ - │ - │ - │ - │ - │ ✔ │
├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glGetnTexImage │ - │ - │ - │ - │ - │ - │ - │ - │ - │ - │ - │ ✔ │
└──────────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘
SEE ALSO
glActiveTexture(), glReadPixels(), glTexImage1D(), glTexImage2D(), glTexImage3D(),
glTexSubImage1D(), glTexSubImage2D(), glTexSubImage3D(), glTexParameter()
COPYRIGHT
Copyright © 1991-2006 Silicon Graphics, Inc. Copyright © 2010-2014 Khronos Group. This
document is licensed under the SGI Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.
COPYRIGHT
Copyright © 1991-2006 Silicon Graphics, Inc.
Copyright © 2010-2014 Khronos Group
[FIXME: source] 01/03/2018 GLGETTEXIMAGE(3G)