glLogicOp(3gl)

1GLLOGICOP(3G)                                                    GLLOGICOP(3G)
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NAME

6       glLogicOp - specify a logical pixel operation for color index rendering
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C SPECIFICATION

10       void glLogicOp( GLenum opcode )
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PARAMETERS

14       opcode  Specifies a symbolic constant that selects a logical operation.
15               The following symbols are accepted: GL_CLEAR, GL_SET,  GL_COPY,
16               GL_COPY_INVERTED,  GL_NOOP,  GL_INVERT, GL_AND, GL_NAND, GL_OR,
17               GL_NOR,  GL_XOR,  GL_EQUIV,  GL_AND_REVERSE,   GL_AND_INVERTED,
18               GL_OR_REVERSE,   and   GL_OR_INVERTED.  The  initial  value  is
19               GL_COPY.
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DESCRIPTION

22       glLogicOp specifies a logical operation that, when enabled, is  applied
23       between  the  incoming color index or RGBA color and the color index or
24       RGBA color at the corresponding  location  in  the  frame  buffer.   To
25       enable  or  disable  the logical operation, call glEnable and glDisable
26       using  the  symbolic  constant  GL_COLOR_LOGIC_OP  for  RGBA  mode   or
27       GL_INDEX_LOGIC_OP  for  color index mode. The initial value is disabled
28       for both operations.
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30                       ───────────────────────────────────────
31                       Opcode             Resulting Operation
32                       ───────────────────────────────────────
33                       GL_CLEAR                    0
34                       GL_SET                      1
35                       GL_COPY                     s
36                       GL_COPY_INVERTED           ~s
37                       GL_NOOP                     d
38                       GL_INVERT                  ~d
39                       GL_AND                    s & d
40                       GL_NAND                 ~(s & d)
41                       GL_OR                     s | d
42                       GL_NOR                  ~(s | d)
43                       GL_XOR                    s ^ d
44                       GL_EQUIV                ~(s ^ d)
45                       GL_AND_REVERSE           s & ~d
46                       GL_AND_INVERTED          ~s & d
47                       GL_OR_REVERSE            s | ~d
48                       GL_OR_INVERTED           ~s | d
49                       ───────────────────────────────────────
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51       opcode is a symbolic constant chosen  from  the  list  above.   In  the
52       explanation  of the logical operations, s represents the incoming color
53       index and d represents the index in the frame buffer.  Standard  C-lan‐
54       guage operators are used.  As these bitwise operators suggest, the log‐
55       ical operation is applied independently to each bit pair of the  source
56       and destination indices or colors.
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NOTES

59       Color index logical operations are always supported. RGBA logical oper‐
60       ations are supported only if the GL version is 1.1 or greater.
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62       When more than one RGBA color or index buffer is enabled  for  drawing,
63       logical  operations  are  performed separately for each enabled buffer,
64       using for the destination  value  the  contents  of  that  buffer  (see
65       glDrawBuffer).
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ERRORS

68       GL_INVALID_ENUM is generated if opcode is not an accepted value.
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70       GL_INVALID_OPERATION  is generated if glLogicOp is executed between the
71       execution of glBegin and the corresponding execution of glEnd.
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ASSOCIATED GETS

74       glGet with argument GL_LOGIC_OP_MODE.
75       glIsEnabled with argument GL_COLOR_LOGIC_OP or GL_INDEX_LOGIC_OP.
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