GLGETTEXIMAGE(3G) UNIX Programmer's Manual GLGETTEXIMAGE(3G)
glGetTexImage - return a texture image
void glGetTexImage( GLenum target,
GLint level,
GLenum format,
GLenum type,
GLvoid *pixels )
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 nth mipmap reduction image.
format Specifies a pixel for the returned data. The sup-
ported 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.
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
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GLGETTEXIMAGE(3G) UNIX Programmer's Manual GLGETTEXIMAGE(3G)
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 com-
ponents, 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 for-
mat 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 pixels.
When the GL_ARB_multitexture extension is supported,
glGetTexImage returns the texture image for the active tex-
ture 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
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GLGETTEXIMAGE(3G) UNIX Programmer's Manual GLGETTEXIMAGE(3G)
GL_BGRA are available only if the GL version is 1.2 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
log2max, where max is the returned value of
GL_MAX_TEXTURE_SIZE.
GL_INVALID_OPERATION is generated if glGetTexImage is exe-
cuted 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.
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
glActiveTextureARB(3G), glDrawPixels(3G), glReadPixels(3G),
glTexEnv(3G), glTexGen(3G), glTexImage1D(3G),
glTexImage2D(3G), glTexImage3D(3G), glTexSubImage1D(3G),
glTexSubImage2D(3G), glTexSubImage3D(3G), glTexParameter(3G)
MirOS BSD #10-current Printed 20.2.2012 3
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