fglMinmax(3G) OpenGL Reference fglMinmax(3G)NAME
fglMinmax - define minmax table
FORTRAN SPECIFICATION
SUBROUTINE fglMinmax( INTEGER*4 target,
INTEGER*4 internalformat,
LOGICAL*1 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 fglGetMinmax. The minmax operation is enabled or
disabled by calling fglEnable or fglDisable, respectively, with an
argument of GL_MINMAX.
fglMinmax 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
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fglMinmax(3G) OpenGL Reference fglMinmax(3G)
pixels are discarded after minmax; no further processing of the pixels
takes place, and no drawing, texture loading, or pixel readback will
result.
NOTES
fglMinmax is present only if GL_ARB_imaging is returned when fglGetString
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 fglMinmax is executed between the
execution of fglBegin and the corresponding execution of fglEnd.
ASSOCIATED GETS
fglGetMinmaxParameter
SEE ALSO
fglGetMinmax, fglResetMinmax
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