IABSD.fr/xenocara/doc/gl-docs/GL/gl/histogram.3gl

Branch : - branch - master - tag -

• Show log

  Commit

• Author : matthieu
  Date : 2006-11-29 17:00:35
  Hash : 36da9a5e
  Message : OpenGL manual pages from monolithic tree.

• doc/gl-docs/GL/gl/histogram.3gl

• '\" te
  '\"! tbl|eqn | mmdoc
  '\"macro stdmacro
  .ds Vn Version 1.2
  .ds Dt 24 September 1999
  .ds Re Release 1.2.1
  .ds Dp Jan 14 18:30
  .ds Dm 01 histogram
  .ds Xs 13152 6 histogram.gl
  .TH GLHISTOGRAM 3G
  .SH NAME
  .B "glHistogram
  \- define histogram table
  
  .SH C SPECIFICATION
  void \f3glHistogram\fP(
  GLenum \fItarget\fP,
  .nf
  .ta \w'\f3void \fPglHistogram( 'u
  	GLsizei \fIwidth\fP,
  	GLenum \fIinternalformat\fP,
  	GLboolean \fIsink\fP )
  .fi
  
  .EQ
  delim $$
  .EN
  .SH PARAMETERS
  .TP \w'\fIinternalformat\fP\ \ 'u 
  \f2target\fP
  The histogram whose parameters are to be set.
  Must be one of
  \%\f3GL_HISTOGRAM\fP or
  \%\f3GL_PROXY_HISTOGRAM\fP.
  .TP
  \f2width\fP
  The number of entries in the histogram table.  Must be a power of 2.
  .TP
  \f2internalformat\fP
  The  of entries in the histogram table.
  Must be one of
  \%\f3GL_ALPHA\fP,
  \%\f3GL_ALPHA4\fP,
  \%\f3GL_ALPHA8\fP,
  \%\f3GL_ALPHA12\fP,
  \%\f3GL_ALPHA16\fP,
  \%\f3GL_LUMINANCE\fP,
  \%\f3GL_LUMINANCE4\fP,
  \%\f3GL_LUMINANCE8\fP,
  \%\f3GL_LUMINANCE12\fP,
  \%\f3GL_LUMINANCE16\fP,
  \%\f3GL_LUMINANCE_ALPHA\fP,
  \%\f3GL_LUMINANCE4_ALPHA4\fP,
  \%\f3GL_LUMINANCE6_ALPHA2\fP,
  \%\f3GL_LUMINANCE8_ALPHA8\fP,
  \%\f3GL_LUMINANCE12_ALPHA4\fP,
  \%\f3GL_LUMINANCE12_ALPHA12\fP,
  \%\f3GL_LUMINANCE16_ALPHA16\fP,
  \%\f3GL_R3_G3_B2\fP,
  \%\f3GL_RGB\fP,
  \%\f3GL_RGB4\fP,
  \%\f3GL_RGB5\fP,
  \%\f3GL_RGB8\fP,
  \%\f3GL_RGB10\fP,
  \%\f3GL_RGB12\fP,
  \%\f3GL_RGB16\fP,
  \%\f3GL_RGBA\fP,
  \%\f3GL_RGBA2\fP,
  \%\f3GL_RGBA4\fP,
  \%\f3GL_RGB5_A1\fP,
  \%\f3GL_RGBA8\fP,
  \%\f3GL_RGB10_A2\fP,
  \%\f3GL_RGBA12\fP, or
  \%\f3GL_RGBA16\fP.
  .TP
  \f2sink\fP
  If \%\f3GL_TRUE\fP, pixels will be consumed by the histogramming
  process and no drawing or texture loading will take place.
  If \%\f3GL_FALSE\fP, pixels will proceed to the minmax process after
  histogramming.
  .SH DESCRIPTION
  When \%\f3GL_HISTOGRAM\fP is enabled, RGBA color components are converted to
  histogram table indices by clamping to the range [0,1], multiplying by
  the width of the histogram table, and rounding to the nearest integer.
  The table entries selected by the RGBA indices are then incremented.
  (If the internal  of the histogram table includes luminance, then
  the index derived from the R color component determines the luminance
  table entry to be incremented.)  If a histogram table entry is incremented
  beyond its maximum value, then its value becomes undefined.  (This is
  not an error.)
  .PP
  Histogramming is performed only for RGBA pixels (though these may
  be specified originally as color indices and converted to RGBA by
  index table lookup).
  Histogramming is enabled with \%\f3glEnable\fP and disabled with \%\f3glDisable\fP.
  .PP
  When \f2target\fP is \%\f3GL_HISTOGRAM\fP, \%\f3glHistogram\fP redefines the current
  histogram table to have \f2width\fP entries of the  specified by
  \f2internalformat\fP.
  The entries are indexed 0 through $"width" ~-~ 1$, and
  all entries are initialized to zero.
  The values in the previous histogram table, if any, are lost.
  If \f2sink\fP is \%\f3GL_TRUE\fP, then pixels are discarded after histogramming;
  no further processing of the pixels takes place, and no drawing,
  texture loading, or pixel readback will result.
  .PP
  When \f2target\fP is \%\f3GL_PROXY_HISTOGRAM\fP, \%\f3glHistogram\fP computes all
  state information as if the histogram table were to be redefined,
  but does not actually define the new table.
  If the requested histogram table is too large to be supported, then the
  state information will be set to zero.
  This provides a way to determine if a histogram table with the given
  parameters can be supported.
  .PP
  .SH NOTES
  \%\f3glHistogram\fP is present only if \%\f3GL_ARB_imaging\fP is returned when \%\f3glGetString\fP
  is called with an argument of \%\f3GL_EXTENSIONS\fP.
  .SH ERRORS
  \%\f3GL_INVALID_ENUM\fP is generated if \f2target\fP is not one of the allowable
  values.
  .P
  \%\f3GL_INVALID_VALUE\fP is generated if \f2width\fP is less than zero or is
  not a power of 2.
  .P
  \%\f3GL_INVALID_ENUM\fP is generated if \f2internalformat\fP is not one of the
  allowable values.
  .P
  \%\f3GL_TABLE_TOO_LARGE\fP is generated if \f2target\fP is \%\f3GL_HISTOGRAM\fP
  and the histogram table specified is too large for the implementation.
  .P
  \%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glHistogram\fP is executed
  between the execution of \%\f3glBegin\fP and the corresponding
  execution of \%\f3glEnd\fP.
  .SH ASSOCIATED GETS
  \%\f3glGetHistogramParameter\fP
  .SH SEE ALSO
  \%\f3glGetHistogram(3G)\fP,
  \%\f3glResetHistogram(3G)\fP