glLogicOp
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## Name

glLogicOp — specify a logical pixel operation for color index rendering

## C Specification

`void `glLogicOp`` | `(` | `GLenum `opcode`);`

## Python Specification

``glLogicOp`` | `(` | ``opcode`) → `None``

## 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 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.

## Notes

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).

## 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

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