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glGetTexImage(3G)
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glGetTexImage - return a texture image
void glGetTexImage(
GLenum target,
GLint level,
GLenum format,
GLenum type,
GLvoid *pixels );
Specifies which texture is to be obtained. GL_TEXTURE_1D,
GL_TEXTURE_2D, and GL_TEXTURE_3D are accepted. 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. 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. 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. 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() 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.
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.
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.
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(3), glDrawPixels(3), glReadPixels(3),
glTexEnv(3), glTexGen(3), glTexImage1D(3), glTexImage2D(3), glTexImage3D(3), glTexSubImage1D(3), glTexSubImage2D(3), glTexSubImage3D(3), glTexParameter(3)
glGetTexImage(3G)
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