glPixelStorei — set pixel storage modes
void glPixelStorei( | GLenum pname, |
GLint param); |
pname
Specifies the symbolic name of the parameter to be set.
One value affects the packing of pixel data into memory:
GL_PACK_ALIGNMENT.
The other affects the unpacking of pixel data from memory:
GL_UNPACK_ALIGNMENT.
param
Specifies the value that pname is set to.
glPixelStorei sets pixel storage modes that affect the operation of subsequent
glReadPixels as well as the unpacking of
texture patterns (see glTexImage2D and
glTexSubImage2D).
pname is a symbolic constant indicating the parameter to be set, and
param is the new value. One storage parameter affects
how pixel data is returned to client memory:
GL_PACK_ALIGNMENTSpecifies 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 storage parameter affects how pixel data is read from client memory:
GL_UNPACK_ALIGNMENTSpecifies 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 glPixelStorei.
pname
| Type | Initial Value | Valid Range |
|---|---|---|---|
GL_PACK_ALIGNMENT
| integer | 4 | 1, 2, 4, or 8 |
GL_UNPACK_ALIGNMENT
| integer | 4 | 1, 2, 4, or 8 |
Boolean parameters are set to false if param is 0 and true otherwise.
GL_INVALID_ENUM is generated if pname is not an accepted value.
GL_INVALID_VALUE is generated if alignment is specified as other than 1, 2, 4, or 8.
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