Интерактивная система просмотра системных руководств (man-ов)
glGetTexImage (3)
>> glGetTexImage (3) ( Разные man: Библиотечные вызовы )
NAME
glGetTexImage
- return a texture image
C SPECIFICATION
void glGetTexImage(
GLenum target,
GLint level,
GLenum format,
GLenum type,
GLvoid *pixels )
delim $$
PARAMETERS
target
Specifies which texture is to be obtained.
GL_TEXTURE_1D, GL_TEXTURE_2D, and GL_TEXTURE_3D are accepted.
level
Specifies the level-of-detail number of the desired image.
Level 0 is the base image level.
Level $n$ is the $n$th mipmap reduction image.
format
Specifies a pixel 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.
pixels
Returns the texture image.
Should be a pointer to an array of the type specified by type.
DESCRIPTION
glGetTexImage returns a texture image into pixels.
target specifies whether the desired texture image is one specified by
glTexImage1D (GL_TEXTURE_1D),
glTexImage2D (GL_TEXTURE_2D), or
glTexImage3D (GL_TEXTURE_3D).
level specifies the level-of-detail number of the desired image.
format and type specify the 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.
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 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.
NOTES
If an error is generated,
no change is made to the contents of pixels.
When the GL_ARB_multitexture extension is supported, glGetTexImage returns
the texture image for the active texture unit.
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.
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 $log sub 2 max$,
where $max$ is the returned value of GL_MAX_TEXTURE_SIZE.
GL_INVALID_OPERATION is generated if glGetTexImage
is executed between the execution of glBegin
and the corresponding execution of glEnd.
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.
ASSOCIATED GETS
glGetTexLevelParameter with argument GL_TEXTURE_WIDTH glGetTexLevelParameter with argument GL_TEXTURE_HEIGHT glGetTexLevelParameter with argument GL_TEXTURE_BORDER glGetTexLevelParameter with argument GL_TEXTURE_INTERNALFORMAT glGet with arguments GL_PACK_ALIGNMENT and others
