glMinmax(3gl)

1GLMINMAX(3G)                                                      GLMINMAX(3G)
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NAME

6       glMinmax - define minmax table
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C SPECIFICATION

10       void glMinmax( GLenum target,
11                      GLenum internalformat,
12                      GLboolean sink )
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PARAMETERS

16       target          The  minmax table whose parameters are to be set.  Must
17                       be GL_MINMAX.
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19       internalformat  The  of entries in the minmax table.  Must  be  one  of
20                       GL_ALPHA, GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16,
21                       GL_LUMINANCE,       GL_LUMINANCE4,       GL_LUMINANCE8,
22                       GL_LUMINANCE12,   GL_LUMINANCE16,   GL_LUMINANCE_ALPHA,
23                       GL_LUMINANCE4_ALPHA4,             GL_LUMINANCE6_ALPHA2,
24                       GL_LUMINANCE8_ALPHA8,            GL_LUMINANCE12_ALPHA4,
25                       GL_LUMINANCE12_ALPHA12,         GL_LUMINANCE16_ALPHA16,
26                       GL_R3_G3_B2,   GL_RGB,   GL_RGB4,   GL_RGB5,   GL_RGB8,
27                       GL_RGB10,  GL_RGB12,   GL_RGB16,   GL_RGBA,   GL_RGBA2,
28                       GL_RGBA4, GL_RGB5_A1, GL_RGBA8, GL_RGB10_A2, GL_RGBA12,
29                       or GL_RGBA16.
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31       sink            If GL_TRUE, pixels  will  be  consumed  by  the  minmax
32                       process  and  no  drawing  or texture loading will take
33                       place.  If GL_FALSE, pixels will proceed to  the  final
34                       conversion process after minmax.
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DESCRIPTION

37       When  GL_MINMAX  is enabled, the RGBA components of incoming pixels are
38       compared to the minimum and maximum values for  each  component,  which
39       are  stored  in  the 2-element minmax table.  (The first element stores
40       the minima, and the second element stores the maxima.)  If a pixel com‐
41       ponent  is greater than the corresponding component in the maximum ele‐
42       ment, then the maximum element is  updated  with  the  pixel  component
43       value.   If  a pixel component is less than the corresponding component
44       in the minimum element, then the minimum element is  updated  with  the
45       pixel  component value.  (In both cases, if the internal  of the minmax
46       table includes luminance, then the R color component of incoming pixels
47       is  used  for  comparison.)   The  contents  of the minmax table may be
48       retrieved at a later time by calling glGetMinmax.  The minmax operation
49       is  enabled or disabled by calling glEnable or glDisable, respectively,
50       with an argument of GL_MINMAX.
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52       glMinmax redefines the current minmax table  to  have  entries  of  the
53       specified  by  internalformat.  The maximum element is initialized with
54       the smallest possible component values, and the minimum element is ini‐
55       tialized with the largest possible component values.  The values in the
56       previous minmax table, if any, are lost.  If sink is GL_TRUE, then pix‐
57       els  are  discarded  after  minmax; no further processing of the pixels
58       takes place, and no drawing, texture loading, or  pixel  readback  will
59       result.
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NOTES

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

66       GL_INVALID_ENUM is generated if target is not one of the allowable val‐
67       ues.
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69       GL_INVALID_ENUM is generated if internalformat is not one of the allow‐
70       able values.
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72       GL_INVALID_OPERATION is generated if glMinmax is executed  between  the
73       execution of glBegin and the corresponding execution of glEnd.
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ASSOCIATED GETS

76       glGetMinmaxParameter
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