GLCOPYCOLORTABLE(3G)GLCOPYCOLORTABLE(3G)NAMEglCopyColorTable - copy pixels into a color table
C SPECIFICATION
void glCopyColorTable( GLenum target,
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.
DESCRIPTIONglCopyColorTable 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].
NOTESglCopyColorTable 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.
ASSOCIATED GETS
glGetColorTable, glGetColorTableParameter
SEE ALSOglColorTable(3G), glColorTableParameter(3G), glReadPixels(3G)
March 1, 2011
