GLGETCONVOLUTIONFILTER(3G)

NAME
glGetConvolutionFilter - get current 1D or 2D convolution filter kernel

C SPECIFICATION
void glGetConvolutionFilter( GLenum target,
	GLenum format,
	GLenum type,
	GLvoid *image )

PARAMETERS

target
    The filter to be retrieved. Must be one of GL_CONVOLUTION_1D or GL_CONVOLUTION_2D.

format
    Format of the output image. 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
    Data type of components in the output image. 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.

image
    Pointer to storage for the output image.

DESCRIPTION
glGetConvolutionFilter returns the current 1D or 2D convolution filter kernel as an image. The one- or two-dimensional image is placed in image according to the specifications in format and type. No pixel transfer operations are performed on this image, but the relevant pixel storage modes are applied.

Color components that are present in format but not included in the internal of the filter are returned as zero. The assignments of internal color components to the components of format are as follows.
 Internal Component    Resulting Component
 red    red
 green    green
 blue    blue
 alpha    alpha
 luminance    red
 intensity    red

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

The current separable 2D filter must be retrieved with glGetSeparableFilter rather than glGetConvolutionFilter.

ERRORS
GL_INVALID_ENUM is generated if target is not one of the allowable values.

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 glGetConvolutionFilter 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.

ASSOCIATED GETS
glGetConvolutionParameter

SEE ALSO
glGetSeparableFilter, glConvolutionParameter, glConvolutionFilter1D, glConvolutionFilter2D