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_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
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.
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.
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.
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 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.
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
glActiveTexture, glReadPixels, glTexImage1D, glTexImage2D, glTexImage3D, glTexSubImage1D, glTexSubImage2D, glTexSubImage3D, glTexParameter
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/.