GLenum internalformat,
GLint x,
GLint y,
GLsizei width )
delim $$
PARAMETERS
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.
DESCRIPTION
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].
NOTES
glCopyColorTable is available only if GL_ARB_imaging is returned from calling
glGetString with an argument of GL_EXTENSIONS.
ERRORS
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.
