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glLogicOp - specify a logical pixel operation for color index rendering
void glLogicOp( GLenum opcode )
- 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.
glLogicOp 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.
| Opcode Resulting Operation |
| 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 |
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.
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).
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.
glGet with argument
GL_LOGIC_OP_MODE.
glIsEnabled with argument GL_COLOR_LOGIC_OP or GL_INDEX_LOGIC_OP.
glAlphaFunc(3G)
,
glBlendFunc(3G)
, glDrawBuffer(3G)
, glEnable(3G)
, glStencilOp(3G)
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