glGetTexImage — return a texture image
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); |
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 is the th 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.
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 |
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.
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 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.
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
| OpenGL Version | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Function / Feature Name | 2.0 | 2.1 | 3.0 | 3.1 | 3.2 | 3.3 | 4.0 | 4.1 | 4.2 | 4.3 | 4.4 | 4.5 |
glGetTexImage
|
✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
glGetTextureImage
|
- | - | - | - | - | - | - | - | - | - | - | ✔ |
glGetnTexImage
|
- | - | - | - | - | - | - | - | - | - | - | ✔ |
glActiveTexture, glReadPixels, glTexImage1D, glTexImage2D, glTexImage3D, glTexSubImage1D, glTexSubImage2D, glTexSubImage3D, glTexParameter
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/.