GLGETHISTOGRAM

Section: Misc. Reference Manual Pages (3G)
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NAME

glGetHistogram - get histogram table

C SPECIFICATION

void glGetHistogram( GLenum target,


                       GLboolean reset,
                       GLenum format,
                       GLenum type,
                       GLvoid *values )

PARAMETERS

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.

DESCRIPTION

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

NOTES

glGetHistogram is present only if GL_ARB_imaging is returned when glGetString is called with an argument of GL_EXTENSIONS.

ERRORS

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.