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Manual Reference Pages  - GLGETHISTOGRAM (3G)

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glGetHistogram - get histogram table

CONTENTS

C Specification
Parameters
Description
Notes
Errors
See Also

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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