GLLOGICOP(3G)GLLOGICOP(3G)NAMEglLogicOp - specify a logical pixel operation for color index rendering
C SPECIFICATION
void glLogicOp( GLenum opcode )
PARAMETERS
opcode Specifies a symbolic constant that selects a logical operation.
The following symbols are accepted: GL_CLEAR, GL_SET, GL_COPY,
GL_COPY_INVERTED, GL_NOOP, GL_INVERT, GL_AND, GL_NAND, GL_OR,
GL_NOR, GL_XOR, GL_EQUIV, GL_AND_REVERSE, GL_AND_INVERTED,
GL_OR_REVERSE, and GL_OR_INVERTED. The initial value is GL_COPY.
DESCRIPTIONglLogicOp specifies a logical operation that, when enabled, is applied
between the incoming color index or RGBA color and the color index or
RGBA color at the corresponding location in the frame buffer. To
enable or disable the logical operation, call glEnable and glDisable
using the symbolic constant GL_COLOR_LOGIC_OP for RGBA mode or
GL_INDEX_LOGIC_OP for color index mode. The initial value is disabled
for both operations.
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Opcode Resulting Operation
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GL_CLEAR 0
GL_SET 1
GL_COPY s
GL_COPY_INVERTED ~s
GL_NOOP d
GL_INVERT ~d
GL_AND s & d
GL_NAND ~(s & d)
GL_OR s | d
GL_NOR ~(s | d)
GL_XOR s ^ d
GL_EQUIV ~(s ^ d)
GL_AND_REVERSE s & ~d
GL_AND_INVERTED ~s & d
GL_OR_REVERSE s | ~d
GL_OR_INVERTED ~s | d
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opcode is a symbolic constant chosen from the list above. In the
explanation of the logical operations, s represents the incoming color
index and d represents the index in the frame buffer. Standard
C-language operators are used. As these bitwise operators suggest, the
logical operation is applied independently to each bit pair of the
source and destination indices or colors.
NOTES
Color index logical operations are always supported. RGBA logical
operations are supported only if the GL version is 1.1 or greater.
When more than one RGBA color or index buffer is enabled for drawing,
logical operations are performed separately for each enabled buffer,
using for the destination value the contents of that buffer (see
glDrawBuffer).
ERRORS
GL_INVALID_ENUM is generated if opcode is not an accepted value.
GL_INVALID_OPERATION is generated if glLogicOp is executed between the
execution of glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGet with argument GL_LOGIC_OP_MODE.
glIsEnabled with argument GL_COLOR_LOGIC_OP or GL_INDEX_LOGIC_OP.
SEE ALSOglAlphaFunc(3G), glBlendFunc(3G), glDrawBuffer(3G), glEnable(3G),
glStencilOp(3G)
March 1, 2011
