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Table of Contents
glCopyColorTable - copy pixels into a color table
void
glCopyColorTable( GLenum target,
GLenum internalformat,
GLint x,
GLint y,
GLsizei width )
eqn not supported
- target
- The color table target. Must be GL_COLOR_TABLE,
GL_POST_CONVOLUTION_COLOR_TABLE, or GL_POST_COLOR_MATRIX_COLOR_TABLE.
- internalformat
- The internal storage of the texture image. Must be one of the following
symbolic constants: GL_ALPHA, GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16,
GL_LUMINANCE, GL_LUMINANCE4, GL_LUMINANCE8, GL_LUMINANCE12, GL_LUMINANCE16,
GL_LUMINANCE_ALPHA, GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8,
GL_LUMINANCE12_ALPHA4, GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16,
GL_INTENSITY, GL_INTENSITY4, GL_INTENSITY8, GL_INTENSITY12, GL_INTENSITY16,
GL_R3_G3_B2, GL_RGB, GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12, GL_RGB16,
GL_RGBA, GL_RGBA2, GL_RGBA4, GL_RGB5_A1, GL_RGBA8, GL_RGB10_A2, GL_RGBA12,
GL_RGBA16.
- x
- The x coordinate of the lower-left corner of the pixel rectangle
to be transferred to the color table.
- y
- The y coordinate of the lower-left
corner of the pixel rectangle to be transferred to the color table.
- width
- The width of the pixel rectangle.
glCopyColorTable loads a color
table with pixels from the current GL_READ_BUFFER (rather than from main
memory, as is the case for glColorTable).
The screen-aligned pixel rectangle
with lower-left corner at (x, y) having width width and height 1 is loaded
into the color table. If any pixels within this region are outside the window
that is associated with the GL context, the values obtained for those pixels
are undefined.
The pixels in the rectangle are processed just as if glReadPixels
were called, with internalformat set to RGBA, but processing stops after
the final conversion to RGBA.
The four scale parameters and the four bias
parameters that are defined for the table are then used to scale and bias
the R, G, B, and A components of each pixel. The scale and bias parameters
are set by calling glColorTableParameter.
Next, the R, G, B, and A values
are clamped to the range [0,1]. Each pixel is then converted to the internal
specified by internalformat. This conversion simply maps the component
values of the pixel (R, G, B, and A) to the values included in the internal
(red, green, blue, alpha, luminance, and intensity). The mapping is as
follows:
| Internal Format Red Green Blue Alpha Luminance Intensity |
| GL_ALPHA A |
| GL_LUMINANCE R |
| GL_LUMINANCE_ALPHA A R |
| GL_INTENSITY R |
| GL_RGB R G B |
| GL_RGBA R G B A |
Finally, the red, green, blue, alpha, luminance, and/or intensity components
of the resulting pixels are stored in the color table. They form a one-dimensional
table with indices in the range [0, width - 1].
glCopyColorTable is available
only if GL_ARB_imaging is returned from calling glGetString with an argument
of GL_EXTENSIONS.
GL_INVALID_ENUM is generated when target is not
one of the allowable values.
GL_INVALID_VALUE is generated if width is less
than zero.
GL_INVALID_VALUE is generated if internalformat is not one of
the allowable values.
GL_TABLE_TOO_LARGE is generated if the requested color
table is too large to be supported by the implementation.
GL_INVALID_OPERATION
is generated if glCopyColorTable is executed between the execution of glBegin
and the corresponding execution of glEnd.
glGetColorTable,
glGetColorTableParameter
glColorTable(3G)
, glColorTableParameter(3G)
,
glReadPixels(3G)
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