glGetHistogram
Get histogram table
C Specification
void glGetHistogram(GLenum target,
GLboolean reset,
GLenum format,
GLenum type,
GLvoid * values);
Parameters
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.
If a nonzero named buffer object is bound to the GL_PIXEL_PACK_BUFFER target (see glBindBuffer) while a histogram table is requested, values is treated as a byte offset into the buffer object’s data store.
Color components that are requested in the specified format, but which are not included in the internal format of the histogram, are returned as zero. The assignments of internal color components to the components requested by format are:
Notes
glGetHistogram is present only if 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 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.
GL_INVALID_OPERATION is generated if a nonzero buffer object name is bound to the GL_PIXEL_PACK_BUFFER target and the buffer object’s data store is currently mapped.
GL_INVALID_OPERATION is generated if a nonzero buffer object name is bound to the GL_PIXEL_PACK_BUFFER target and the data would be packed to the buffer object such that the memory writes required would exceed the data store size.
GL_INVALID_OPERATION is generated if a nonzero buffer object name is bound to the GL_PIXEL_PACK_BUFFER target and values is not evenly divisible into the number of bytes needed to store in memory a datum indicated by type.
GL_INVALID_OPERATION is generated if glGetHistogram is executed between the execution of glBegin and the corresponding execution of glEnd.
Associated Gets
glGetHistogramParameter
glGet with argument GL_PIXEL_PACK_BUFFER_BINDING
See Also
glHistogram, glResetHistogram,
glGetHistogramParameter
C Specification
void glGetHistogramParameterfv(GLenum target,
GLenum pname,
GLfloat * params);
void glGetHistogramParameteriv(GLenum target,
GLenum pname,
GLint * params);
Parameters
Description
glGetHistogramParameter is used to query parameter values for the current histogram or for a proxy. The histogram state information may be queried by calling glGetHistogramParameter with a target of GL_HISTOGRAM (to obtain information for the current histogram table) or GL_PROXY_HISTOGRAM (to obtain information from the most recent proxy request) and one of the following values for the pname argument:
Notes
glGetHistogramParameter is present only if ARB_imaging is returned when glGetString is called with an argument of GL_EXTENSIONS.
Errors
GL_INVALID_ENUM is generated if target is not one of the allowable values.
GL_INVALID_ENUM is generated if pname is not one of the allowable values.
GL_INVALID_OPERATION is generated if glGetHistogramParameter is executed between the execution of glBegin and the corresponding execution of glEnd.
See Also
glGetHistogram, glHistogram
glGetLight
Return light source parameter values
C Specification
void glGetLightfv(GLenum light,
GLenum pname,
GLfloat * params);
void glGetLightiv(GLenum light,
GLenum pname,
GLint * params);
Parameters
Description
glGetLight returns in params the value or values of a light source parameter. light names the light and is a symbolic name of the form GL_LIGHTi where i ranges from 0 to the value of GL_MAX_LIGHTS - 1. GL_MAX_LIGHTS is an implementation dependent constant that is greater than or equal to eight. pname specifies one of ten light source parameters, again by symbolic name.
The following parameters are defined:
GL_AMBIENT
params returns four integer or floating-point values representing the ambient intensity of the light source. Integer values, when requested, are linearly mapped from the internal floating-point representation such that 1.0 maps to the most positive representable integer value, and -1.0 maps to the most negative representable integer value. If the internal value is outside the range [-1,1], the corresponding integer return value is undefined. The initial value is (0, 0, 0, 1).
GL_DIFFUSE
params returns four integer or floating-point values representing the diffuse intensity of the light source. Integer values, when requested, are linearly mapped from the internal floating-point representation such that 1.0 maps to the most positive representable integer value, and -1.0 maps to the most negative representable integer value. If the internal value is outside the range [-1,1], the corresponding integer return value is undefined. The initial value for GL_LIGHT0 is (1, 1, 1, 1); for other lights, the initial value is (0, 0, 0, 0).
GL_SPECULAR
params returns four integer or floating-point values representing the specular intensity of the light source. Integer values, when requested, are linearly mapped from the internal floating-point representation such that 1.0 maps to the most positive representable integer value, and -1.0 maps to the most negative representable integer value. If the internal value is outside the range [-1,1], the corresponding integer return value is undefined. The initial value for GL_LIGHT0 is (1, 1, 1, 1); for other lights, the initial value is (0, 0, 0, 0).
GL_POSITION