Glpixelstore - HP b2600 Reference Manual

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glPixelStore

glPixelStore
glPixelStoref, glPixelStorei: set pixel storage modes.
C Specification
void glPixelStoref(
void glPixelStorei(
Parameters
pname
param
Description
glPixelStore sets pixel storage modes that affect the operation of subsequent
glDrawPixels and glReadPixels as well as the unpacking of polygon stipple patterns (see
glPolygonStipple), bitmaps (see glBitmap), and texture patterns (see glTexImage1D,
glTexImage2D, glTexSubImage1D, and glTexSubImage2D).
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, and are therefore significant only for glReadPixels commands.
They are as follows:
GL_PACK_SWAP_BYTES
If true, byte ordering for multibyte color components, depth components, color indices, or
stencil indices is reversed. That is, if a four-byte component consists of bytes b
b
3
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
328
GLenum pname,
GLfloat param)
GLenum pname,
GLint param)
Specifies 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_SKIP_PIXELS,
GL_PACK_SKIP_ROWS, 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_SKIP_PIXELS,
GL_UNPACK_SKIP_ROWS, and GL_UNPACK_ALIGNMENT.
Specifies the value that pname is set to.
, it is stored in memory as b , b , b , b if GL_PACK_SWAP_BYTES is true.
3 2 1 0
, b , b ,
0 1 2
Chapter 14