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glGetHistogram - get histogram table
void glGetHistogram(
GLenum target,
GLboolean reset,
GLenum format,
GLenum type,
GLvoid *values )
- target
- Must be GL_HISTOGRAM.
- reset
- If GL_TRUE, each component
counter that is actually returned is reset to zero. (Other counters are
unaffected.) If GL_FALSE, none of the counters in the histogram table is
modified.
- format
- The of values to be returned in values. Must be one of
GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_BGR, GL_RGBA, GL_BGRA,
GL_LUMINANCE, or GL_LUMINANCE_ALPHA.
- type
- The type of values to be returned
in values. Symbolic constants GL_UNSIGNED_BYTE, GL_BYTE, GL_BITMAP, 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 are accepted.
- values
- A pointer to storage
for the returned histogram table.
glGetHistogram returns the
current histogram table as a one-dimensional image with the same width as
the histogram. No pixel transfer operations are performed on this image,
but pixel storage modes that are applicable to 1D images are honored.
Color
components that are requested in the specified format, but which are not
included in the internal of the histogram, are returned as zero. The assignments
of internal color components to the components requested by format are:
| Internal Component Resulting Component |
| Red Red |
| Green Green |
| Blue Blue |
| Alpha Alpha |
| Luminance Red |
glGetHistogram is present only if GL_ARB_imaging is returned when
glGetString is called with an argument of GL_EXTENSIONS.
GL_INVALID_ENUM
is generated if target is not GL_HISTOGRAM.
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_INVALID_OPERATION is generated
if glGetHistogram is executed between the execution of glBegin and the
corresponding execution of glEnd.
GL_INVALID_OPERATION is generated if type
is one of GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5,
or GL_UNSIGNED_SHORT_5_6_5_REV and format is not GL_RGB.
GL_INVALID_OPERATION
is generated if type is one of 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, or GL_UNSIGNED_INT_2_10_10_10_REV
and format is neither GL_RGBA nor GL_BGRA.
glHistogram(3G)
, glResetHistogram(3G)
,
glGetHistogramParameter(3G)
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