Страницы справочника OS X

Эта страница руководства является частью версии 5.0 Инструментов XCode

Читать страницы руководства

GLCOLORTABLE(3G)                                                                            GLCOLORTABLE(3G)



NAME
       glColorTable - define a color lookup table


C SPECIFICATION
       void glColorTable( GLenum target,
                          GLenum internalformat,
                          GLsizei width,
                          GLenum format,
                          GLenum type,
                          const GLvoid *table )


PARAMETERS
       target          Must      be      one     of     GL_COLOR_TABLE,     GL_POST_CONVOLUTION_COLOR_TABLE,
                       GL_POST_COLOR_MATRIX_COLOR_TABLE,                               GL_PROXY_COLOR_TABLE,
                       GL_PROXY_POST_CONVOLUTION_COLOR_TABLE, or GL_PROXY_POST_COLOR_MATRIX_COLOR_TABLE.

       internalformat  The  internal   of  the  color  table.  The allowable values are 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, and GL_RGBA16.

       width           The number of entries in the color lookup table specified by table.

       format          The  of the pixel data in table.  The allowable values are GL_RED, GL_GREEN, GL_BLUE,
                       GL_ALPHA, GL_LUMINANCE, GL_LUMINANCE_ALPHA, GL_RGB, GL_BGR, GL_RGBA, and GL_BGRA.

       type            The  type  of  the  pixel  data in table.  The allowable values are GL_UNSIGNED_BYTE,
                       GL_BYTE,   GL_UNSIGNED_SHORT,   GL_SHORT,    GL_UNSIGNED_INT,    GL_INT,    GL_FLOAT,
                       GL_UNSIGNED_BYTE_3_3_2,      GL_UNSIGNED_BYTE_2_3_3_REV,     GL_UNSIGNED_SHORT_5_6_5,
                       GL_UNSIGNED_SHORT_5_6_5_REV,                               GL_UNSIGNED_SHORT_4_4_4_4,
                       GL_UNSIGNED_SHORT_4_4_4_4_REV,                             GL_UNSIGNED_SHORT_5_5_5_1,
                       GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8,  GL_UNSIGNED_INT_8_8_8_8_REV,
                       GL_UNSIGNED_INT_10_10_10_2, and GL_UNSIGNED_INT_2_10_10_10_REV.

       table           Pointer to a one-dimensional array of pixel data that is processed to build the color
                       table.

DESCRIPTION
       glColorTable may be used in two ways: to test the actual size and color resolution of a lookup  table
       given  a particular set of parameters, or to load the contents of a color lookup table.  Use the tar-gets targets
       gets GL_PROXY_* for the first case and the other targets for the second case.

       If target is GL_COLOR_TABLE,  GL_POST_CONVOLUTION_COLOR_TABLE,  or  GL_POST_COLOR_MATRIX_COLOR_TABLE,
       glColorTable  builds  a  color  lookup  table  from an array of pixels.  The pixel array specified by
       width, format, type, and table is extracted from memory and processed just as  if  glDrawPixels  were
       called, but processing stops after the final expansion to RGBA is completed.

       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.   (Use  glColorTableParameter  to  set
       these scale and bias parameters.)

       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     Channel mapping
        GL_ALPHA            A=Alpha
        GL_LUMINANCE        R=Luminance
        GL_LUMINANCE_ALPHA  A=Alpha, R=Luminance
        GL_INTENSITY        R=Intensity
        GL_RGB              R=Red, G=Green, B=Blue
        GL_RGBA             R=Red, G=Green, B=Blue, A=Alpha


       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].

       If target is GL_PROXY_*, glColorTable recomputes and stores the values of  the  proxy  color  table's
       state     variables     GL_COLOR_TABLE_FORMAT,     GL_COLOR_TABLE_WIDTH,     GL_COLOR_TABLE_RED_SIZE,
       GL_COLOR_TABLE_GREEN_SIZE,            GL_COLOR_TABLE_BLUE_SIZE,            GL_COLOR_TABLE_ALPHA_SIZE,
       GL_COLOR_TABLE_LUMINANCE_SIZE, and GL_COLOR_TABLE_INTENSITY_SIZE.  There is no effect on the image or
       state of any actual color table.  If the specified color table is too large to be supported, then all
       the  proxy  state  variables  listed above are set to zero.  Otherwise, the color table could be sup-ported supported
       ported by glColorTable using the corresponding non-proxy target, and the proxy  state  variables  are
       set as if that target were being defined.

       The  proxy  state  variables  can  be  retrieved by calling glGetColorTableParameter with a target of
       GL_PROXY_*.  This allows the application to decide if a particular glColorTable  command  would  suc-ceed, succeed,
       ceed, and to determine what the resulting color table attributes would be.

       If  a color table is enabled, and its width is non-zero, then its contents are used to replace a sub-set subset
       set of the components of each RGBA pixel group, based on the internal  of the table.

       Each pixel group has color components (R, G, B, A) that are in the range [0.0, 1.0].  The color  com-ponents components
       ponents  are  rescaled  to the size of the color lookup table to form an index.  Then a subset of the
       components based on the internal  of the table are replaced by  the  table  entry  selected  by  that
       index.  If the color components and contents of the table are represented as follows:


       Representation     Meaning
        r                  Table index computed from R
        g                  Table index computed from G
        b                  Table index computed from B
        a                  Table index computed from A
        L[i]               Luminance value at table index i
        I[i]               Intensity value at table index i
        R[i]               Red value at table index i
        G[i]               Green value at table index i
        B[i]               Blue value at table index i
        A[i]               Alpha value at table index i


       then the result of color table lookup is as follows:


        Table Internal     Resulting Texture Components
        Format             R     G     B     A

        GL_ALPHA           R     G     B     A[a]
        GL_LUMINANCE       L[r]  L[g]  L[b]  At
        GL_LUMINANCE_ALPHA L[r]  L[g]  L[b]  A[a]
        GL_INTENSITY       I[r]  I[g]  I[b]  I[a]
        GL_RGB             R[r]  G[g]  B[b]  A
        GL_RGBA            R[r]  G[g]  B[b]  A[a]



       When  GL_COLOR_TABLE is enabled, the colors resulting from the pixel map operation (if it is enabled)
       are mapped by the color lookup table before being passed to the  convolution  operation.  The  colors
       resulting from the convolution operation are modified by the post convolution color lookup table when
       GL_POST_CONVOLUTION_COLOR_TABLE is enabled. These modified colors are then sent to the  color  matrix
       operation.   Finally,  if  GL_POST_COLOR_MATRIX_COLOR_TABLE is enabled, the colors resulting from the
       color matrix operation are mapped by the post color matrix color lookup table before  being  used  by
       the histogram operation.


NOTES
       glColorTable  is  present only if GL_ARB_imaging is returned when glGetString is called with an argu-ment argument
       ment of GL_EXTENSIONS.

       If     target     is     set     to     GL_COLOR_TABLE,      GL_POST_CONVOLUTION_COLOR_TABLE,      or
       GL_POST_COLOR_MATRIX_COLOR_TABLE,  then  width  must be a power of two or a GL_INVALID_VALUE error is
       generated.


ERRORS
       GL_INVALID_ENUM is generated if target is not one of the allowable values.

       GL_INVALID_ENUM is generated if internalformat is not one of the allowable values.

       GL_INVALID_VALUE is generated if width is less than zero.

       GL_INVALID_ENUM is generated if format is not one of the allowable values.

       GL_INVALID_ENUM is generated if type 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, and target is not a GL_PROXY_* target.

       GL_INVALID_OPERATION  is  generated  if glColorTable is executed between the execution of glBegin and
       the corresponding execution of glEnd.

ASSOCIATED GETS
       glGetColorTableParameter

SEE ALSO
       glColorSubTable(3G), glColorTableParameter(3G), glCopyColorTable(3G), glCopyColorSubTable(3G), glGetColorTable(3G)




                                                                                            GLCOLORTABLE(3G)