glCopyColorTable — copy pixels into a color table
void glCopyColorTable( | GLenum | target, |
| GLenum | internalformat, | |
| GLint | x, | |
| GLint | y, | |
| GLsizei | width); |
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 format 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, or
GL_RGBA16.
xThe x coordinate of the lower-left corner of the pixel rectangle to be transferred to the color table.
yThe y coordinate of the lower-left corner of the pixel rectangle to be transferred to the color table.
widthThe 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
internalformat. This conversion simply maps the component values of the pixel (R, G, B,
and A) to the values included in the internal format (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
glCopyColorTable is available only if 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.
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.