GLCOPYCOLORTABLE(3G)UNIX Programmer's Manual GLCOPYCOLORTABLE(3G)
NAME
glCopyColorTable - copy pixels into a color table
C SPECIFICATION
void glCopyColorTable( GLenum target,
GLenum internalformat,
GLint x,
GLint y,
GLsizei width )
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 con-
stants: 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).
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GLCOPYCOLORTABLE(3G)UNIX Programmer's Manual GLCOPYCOLORTABLE(3G)
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 speci-
fied by internalformat. This conversion simply maps the com-
ponent values of the pixel (R, G, B, and A) to the values
included in the internal (red, green, blue, alpha, lumi-
nance, 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.
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GLCOPYCOLORTABLE(3G)UNIX Programmer's Manual GLCOPYCOLORTABLE(3G)
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.
ASSOCIATED GETS
glGetColorTable, glGetColorTableParameter
SEE ALSO
glColorTable(3G), glColorTableParameter(3G),
glReadPixels(3G)
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