GLGETHISTOGRAM(3G)

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.

SEE ALSO
glHistogram, glResetHistogram, glGetHistogramParameter