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glLogicOp

Chapter 10

267

glLogicOp

glLogicOp: 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.

Description

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 Value

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

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