glMinmax(3G)

NAME
     glMinmax - define minmax table


C SPECIFICATION
     void glMinmax( GLenum target,
                    GLenum internalformat,
                    GLboolean sink )


PARAMETERS
     target          The minmax table whose parameters are to be set.  Must be
                     GL_MINMAX.

     internalformat  The format of entries in the minmax table.  Must be one
                     of 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_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.

     sink            If GL_TRUE, pixels will be consumed by the minmax process
                     and no drawing or texture loading will take place.  If
                     GL_FALSE, pixels will proceed to the final conversion
                     process after minmax.

DESCRIPTION
     When GL_MINMAX is enabled, the RGBA components of incoming pixels are
     compared to the minimum and maximum values for each component, which are
     stored in the 2-element minmax table.  (The first element stores the
     minima, and the second element stores the maxima.)  If a pixel component
     is greater than the corresponding component in the maximum element, then
     the maximum element is updated with the pixel component value.  If a
     pixel component is less than the corresponding component in the minimum
     element, then the minimum element is updated with the pixel component
     value.  (In both cases, if the internal format of the minmax table
     includes luminance, then the R color component of incoming pixels is used
     for comparison.)  The contents of the minmax table may be retrieved at a
     later time by calling glGetMinmax.  The minmax operation is enabled or
     disabled by calling glEnable or glDisable, respectively, with an argument
     of GL_MINMAX.

     glMinmax redefines the current minmax table to have entries of the format
     specified by internalformat.  The maximum element is initialized with the
     smallest possible component values, and the minimum element is
     initialized with the largest possible component values.  The values in
     the previous minmax table, if any, are lost.  If sink is GL_TRUE, then
     pixels are discarded after minmax; no further processing of the pixels
     takes place, and no drawing, texture loading, or pixel readback will
     result.

NOTES
     glMinmax is present only if GL_ARB_imaging is returned when glGetString
     is called with an argument of GL_EXTENSIONS.

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_OPERATION is generated if glMinmax is executed between the
     execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS
     glGetMinmaxParameter


SEE ALSO
     glGetMinmax, glResetMinmax