table of contents
GLPIXELSTORE(3G) | [FIXME: manual] | GLPIXELSTORE(3G) |
NAME¶
glPixelStore - set pixel storage modesC SPECIFICATION¶
void glPixelStoref(GLenum pname,
GLfloat param);
void glPixelStorei(GLenum pname,
GLint param);
PARAMETERS¶
pnameSpecifies the symbolic name of the parameter to be set.
Six values affect the packing of pixel data into memory:
GL_PACK_SWAP_BYTES, GL_PACK_LSB_FIRST,
GL_PACK_ROW_LENGTH, GL_PACK_IMAGE_HEIGHT,
GL_PACK_SKIP_PIXELS, GL_PACK_SKIP_ROWS,
GL_PACK_SKIP_IMAGES, and GL_PACK_ALIGNMENT. Six more affect the
unpacking of pixel data from memory: GL_UNPACK_SWAP_BYTES,
GL_UNPACK_LSB_FIRST, GL_UNPACK_ROW_LENGTH,
GL_UNPACK_IMAGE_HEIGHT, GL_UNPACK_SKIP_PIXELS,
GL_UNPACK_SKIP_ROWS, GL_UNPACK_SKIP_IMAGES, and
GL_UNPACK_ALIGNMENT.
param
Specifies the value that pname is set to.
DESCRIPTION¶
glPixelStore sets pixel storage modes that affect the operation of subsequent glReadPixels() as well as the unpacking of texture patterns (see glTexImage1D(), glTexImage2D(), glTexImage3D(), glTexSubImage1D(), glTexSubImage2D(), glTexSubImage3D()), glCompressedTexImage1D(), glCompressedTexImage2D(), glCompressedTexImage3D(), glCompressedTexSubImage1D(), glCompressedTexSubImage2D() or glCompressedTexSubImage1D(). pname is a symbolic constant indicating the parameter to be set, and param is the new value. Six of the twelve storage parameters affect how pixel data is returned to client memory. They are as follows: GL_PACK_SWAP_BYTESIf true, byte ordering for multibyte color components,
depth components, or stencil indices is reversed. That is, if a four-byte
component consists of bytes b 0, b 1, b 2, b 3, it is stored in memory as b 3,
b 2, b 1, b 0 if GL_PACK_SWAP_BYTES is true. GL_PACK_SWAP_BYTES
has no effect on the memory order of components within a pixel, only on the
order of bytes within components or indices. For example, the three components
of a GL_RGB format pixel are always stored with red first, green
second, and blue third, regardless of the value of
GL_PACK_SWAP_BYTES.
GL_PACK_LSB_FIRST
If true, bits are ordered within a byte from least
significant to most significant; otherwise, the first bit in each byte is the
most significant one.
GL_PACK_ROW_LENGTH
If greater than 0, GL_PACK_ROW_LENGTH defines the
number of pixels in a row. If the first pixel of a row is placed at location p
in memory, then the location of the first pixel of the next row is obtained by
skipping
k = n l a s s n l a s >= a s
< a
components or indices, where n is the number of components or indices in a
pixel, l is the number of pixels in a row ( GL_PACK_ROW_LENGTH if it is
greater than 0, the width argument to the pixel routine otherwise), a is the
value of GL_PACK_ALIGNMENT, and s is the size, in bytes, of a single
component (if a < s, then it is as if a = s). In the case of 1-bit values,
the location of the next row is obtained by skipping
k = 8 a n l 8 a
components or indices.
The word component in this description refers to the nonindex values red,
green, blue, alpha, and depth. Storage format GL_RGB, for example, has
three components per pixel: first red, then green, and finally blue.
GL_PACK_IMAGE_HEIGHT
If greater than 0, GL_PACK_IMAGE_HEIGHT defines
the number of pixels in an image three-dimensional texture volume, where
``image'' is defined by all pixels sharing the same third dimension index. If
the first pixel of a row is placed at location p in memory, then the location
of the first pixel of the next row is obtained by skipping
k = n l h a s s n l h a
s >= a s < a
components or indices, where n is the number of components or indices in a
pixel, l is the number of pixels in a row ( GL_PACK_ROW_LENGTH if it is
greater than 0, the width argument to glTexImage3D() otherwise), h is
the number of rows in a pixel image ( GL_PACK_IMAGE_HEIGHT if it is
greater than 0, the height argument to the glTexImage3D() routine
otherwise), a is the value of GL_PACK_ALIGNMENT, and s is the size, in
bytes, of a single component (if a < s, then it is as if a = s).
The word component in this description refers to the nonindex values red,
green, blue, alpha, and depth. Storage format GL_RGB, for example, has
three components per pixel: first red, then green, and finally blue.
GL_PACK_SKIP_PIXELS, GL_PACK_SKIP_ROWS, and
GL_PACK_SKIP_IMAGES
These values are provided as a convenience to the
programmer; they provide no functionality that cannot be duplicated simply by
incrementing the pointer passed to glReadPixels(). Setting
GL_PACK_SKIP_PIXELS to i is equivalent to incrementing the pointer by i
n components or indices, where n is the number of components or
indices in each pixel. Setting GL_PACK_SKIP_ROWS to j is equivalent to
incrementing the pointer by j m components or indices, where m is the
number of components or indices per row, as just computed in the
GL_PACK_ROW_LENGTH section. Setting GL_PACK_SKIP_IMAGES to k is
equivalent to incrementing the pointer by k p, where p is the number
of components or indices per image, as computed in the
GL_PACK_IMAGE_HEIGHT section.
GL_PACK_ALIGNMENT
Specifies the alignment requirements for the start of
each pixel row in memory. The allowable values are 1 (byte-alignment), 2 (rows
aligned to even-numbered bytes), 4 (word-alignment), and 8 (rows start on
double-word boundaries).
The other six of the twelve storage parameters affect how pixel data is read
from client memory. These values are significant for glTexImage1D(),
glTexImage2D(), glTexImage3D(), glTexSubImage1D(),
glTexSubImage2D(), and glTexSubImage3D()
They are as follows:
GL_UNPACK_SWAP_BYTES
If true, byte ordering for multibyte color components,
depth components, or stencil indices is reversed. That is, if a four-byte
component consists of bytes b 0, b 1, b 2, b 3, it is taken from memory as b
3, b 2, b 1, b 0 if GL_UNPACK_SWAP_BYTES is true.
GL_UNPACK_SWAP_BYTES has no effect on the memory order of components
within a pixel, only on the order of bytes within components or indices. For
example, the three components of a GL_RGB format pixel are always
stored with red first, green second, and blue third, regardless of the value
of GL_UNPACK_SWAP_BYTES.
GL_UNPACK_LSB_FIRST
If true, bits are ordered within a byte from least
significant to most significant; otherwise, the first bit in each byte is the
most significant one.
GL_UNPACK_ROW_LENGTH
If greater than 0, GL_UNPACK_ROW_LENGTH defines
the number of pixels in a row. If the first pixel of a row is placed at
location p in memory, then the location of the first pixel of the next row is
obtained by skipping
k = n l a s s n l a s >= a s
< a
components or indices, where n is the number of components or indices in a
pixel, l is the number of pixels in a row ( GL_UNPACK_ROW_LENGTH if it
is greater than 0, the width argument to the pixel routine otherwise), a is
the value of GL_UNPACK_ALIGNMENT, and s is the size, in bytes, of a
single component (if a < s, then it is as if a = s). In the case of 1-bit
values, the location of the next row is obtained by skipping
k = 8 a n l 8 a
components or indices.
The word component in this description refers to the nonindex values red,
green, blue, alpha, and depth. Storage format GL_RGB, for example, has
three components per pixel: first red, then green, and finally blue.
GL_UNPACK_IMAGE_HEIGHT
If greater than 0, GL_UNPACK_IMAGE_HEIGHT defines
the number of pixels in an image of a three-dimensional texture volume. Where
``image'' is defined by all pixel sharing the same third dimension index. If
the first pixel of a row is placed at location p in memory, then the location
of the first pixel of the next row is obtained by skipping
k = n l h a s s n l h a
s >= a s < a
components or indices, where n is the number of components or indices in a
pixel, l is the number of pixels in a row ( GL_UNPACK_ROW_LENGTH if it
is greater than 0, the width argument to glTexImage3D() otherwise), h
is the number of rows in an image ( GL_UNPACK_IMAGE_HEIGHT if it is
greater than 0, the height argument to glTexImage3D() otherwise), a is
the value of GL_UNPACK_ALIGNMENT, and s is the size, in bytes, of a
single component (if a < s, then it is as if a = s).
The word component in this description refers to the nonindex values red,
green, blue, alpha, and depth. Storage format GL_RGB, for example, has
three components per pixel: first red, then green, and finally blue.
GL_UNPACK_SKIP_PIXELS and GL_UNPACK_SKIP_ROWS
These values are provided as a convenience to the
programmer; they provide no functionality that cannot be duplicated by
incrementing the pointer passed to glTexImage1D(),
glTexImage2D(), glTexSubImage1D() or glTexSubImage2D().
Setting GL_UNPACK_SKIP_PIXELS to i is equivalent to incrementing the
pointer by i n components or indices, where n is the number of
components or indices in each pixel. Setting GL_UNPACK_SKIP_ROWS to j
is equivalent to incrementing the pointer by j k components or
indices, where k is the number of components or indices per row, as just
computed in the GL_UNPACK_ROW_LENGTH section.
GL_UNPACK_ALIGNMENT
Specifies the alignment requirements for the start of
each pixel row in memory. The allowable values are 1 (byte-alignment), 2 (rows
aligned to even-numbered bytes), 4 (word-alignment), and 8 (rows start on
double-word boundaries).
The following table gives the type, initial value, and range of valid values for
each storage parameter that can be set with glPixelStore.
pname | Type | Initial Value | Valid Range |
GL_PACK_SWAP_BYTES | boolean | false | true or false |
GL_PACK_LSB_FIRST | boolean | false | true or false |
GL_PACK_ROW_LENGTH | integer | 0 | 0 ∞ |
GL_PACK_IMAGE_HEIGHT | integer | 0 | 0 ∞ |
GL_PACK_SKIP_ROWS | integer | 0 | 0 ∞ |
GL_PACK_SKIP_PIXELS | integer | 0 | 0 ∞ |
GL_PACK_SKIP_IMAGES | integer | 0 | 0 ∞ |
GL_PACK_ALIGNMENT | integer | 4 | 1, 2, 4, or 8 |
GL_UNPACK_SWAP_BYTES | boolean | false | true or false |
GL_UNPACK_LSB_FIRST | boolean | false | true or false |
GL_UNPACK_ROW_LENGTH | integer | 0 | 0 ∞ |
GL_UNPACK_IMAGE_HEIGHT | integer | 0 | 0 ∞ |
GL_UNPACK_SKIP_ROWS | integer | 0 | 0 ∞ |
GL_UNPACK_SKIP_PIXELS | integer | 0 | 0 ∞ |
GL_UNPACK_SKIP_IMAGES | integer | 0 | 0 ∞ |
GL_UNPACK_ALIGNMENT | integer | 4 | 1, 2, 4, or 8 |
ERRORS¶
GL_INVALID_ENUM is generated if pname is not an accepted value. GL_INVALID_VALUE is generated if a negative row length, pixel skip, or row skip value is specified, or if alignment is specified as other than 1, 2, 4, or 8.ASSOCIATED GETS¶
glGet() with argument GL_PACK_SWAP_BYTES glGet() with argument GL_PACK_LSB_FIRST glGet() with argument GL_PACK_ROW_LENGTH glGet() with argument GL_PACK_IMAGE_HEIGHT glGet() with argument GL_PACK_SKIP_ROWS glGet() with argument GL_PACK_SKIP_PIXELS glGet() with argument GL_PACK_SKIP_IMAGES glGet() with argument GL_PACK_ALIGNMENT glGet() with argument GL_UNPACK_SWAP_BYTES glGet() with argument GL_UNPACK_LSB_FIRST glGet() with argument GL_UNPACK_ROW_LENGTH glGet() with argument GL_UNPACK_IMAGE_HEIGHT glGet() with argument GL_UNPACK_SKIP_ROWS glGet() with argument GL_UNPACK_SKIP_PIXELS glGet() with argument GL_UNPACK_SKIP_IMAGES glGet() with argument GL_UNPACK_ALIGNMENTVERSION SUPPORT¶
OpenGL Version | ||||||||||||
Function / Feature Name | 2.0 | 2.1 | 3.0 | 3.1 | 3.2 | 3.3 | 4.0 | 4.1 | 4.2 | 4.3 | 4.4 | 4.5 |
glPixelStoref | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
glPixelStorei | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
SEE ALSO¶
glReadPixels(), glTexImage1D(), glTexImage2D(), glTexImage3D(), glTexSubImage1D(), glTexSubImage2D(), glTexSubImage3D(), glCompressedTexImage1D(), glCompressedTexImage2D(), glCompressedTexImage3D(), glCompressedTexSubImage1D(), glCompressedTexSubImage2D(), glCompressedTexSubImage1D().COPYRIGHT¶
Copyright © 1991-2006 Silicon Graphics, Inc. Copyright © 2010-2014 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.COPYRIGHT¶
Copyright © 1991-2006 Silicon Graphics, Inc.08/26/2014 | [FIXME: source] |