glLogicOp(3G)glLogicOp(3G)NAMEglLogicOp - specify a logical pixel operation for color index rendering
SYNOPSIS
void glLogicOp(
GLenum opcode );
PARAMETERS
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 glDis‐
able() 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 expla‐
nation 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 oper‐
ations 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 GETSglGet() with argument GL_LOGIC_OP_MODE
glIsEnabled() with argument GL_COLOR_LOGIC_OP or GL_INDEX_LOGIC_OP
SEE ALSOglAlphaFunc(3), glBlendFunc(3), glDrawBuffer(3), glEnable(3), glSten‐
cilOp(3)glLogicOp(3G)