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GLLOGICOP()							   GLLOGICOP()

NAME
       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  en-
       able  or	disable	the logical operation, call glEnable and glDisable us-
       ing the symbolic	constant GL_COLOR_LOGIC_OP for	RGBA  mode  or	GL_IN-
       DEX_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	    |
			| GL_OR_REVERSE	  |	s | ~d	    |
			| GL_OR_INVERTED  |	~s | d	    |
			+-----------------+-----------------+
       opcode is a symbolic constant chosen from the list above.  In  the  ex-
       planation  of  the  logical operations, s represents the	incoming color
       index and d represents the index	in the frame buffer.  Standard	C-lan-
       guage operators are used.  As these bitwise operators suggest, the log-
       ical 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  gl-
       DrawBuffer).

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 ALSO
       glAlphaFunc, glBlendFunc, glDrawBuffer, glEnable, glStencilOp

								   GLLOGICOP()

NAME | C SPECIFICATION | PARAMETERS | DESCRIPTION | NOTES | ERRORS | ASSOCIATED GETS | SEE ALSO

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