glLogicOp: specify a logical pixel operation for color index
C Specification |
Associated Gets |
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.
- Specifies a symbolic constant that selects a logical operation. The
following symbols are accepted: GL_CLEAR,
GL_NAND, GL_OR, GL_NOR,
GL_OR_REVERSE, and GL_OR_INVERTED. The
initial value is GL_COPY.
||s & d|
||! (s & d)|
||s | d|
||! (s | d)|
||s ^ d|
||! (s ^ d)|
||s & !d|
||!s & d|
||s | !d|
||!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).
glGet with argument
- 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.
glIsEnabled with argument
GL_COLOR_LOGIC_OP or GL_INDEX_LOGIC_OP.