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.
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 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,
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 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,
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 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 Khronos
Group. This document is licensed under the SGI Free Software B License. For
details, see
http://oss.sgi.com/projects/FreeB/.