glConvolutionFilter2DEXT

NAME

C SPECIFICATION

void glConvolutionFilter2DEXT(GLenum target,
                              GLenum internalformat,
                              GLsizei width,
                              GLsizei height,
                              GLenum format,
                              GLenum type,
                              const GLvoid *image)

PARAMETERS

DESCRIPTION

The R, G, B, and A components of each pixel are scaled by the four 2D GL_CONVOLUTION_FILTER_SCALE_EXT parameters and biased by the four 2D GL_CONVOLUTION_FILTER_BIAS_EXT parameters. (The scale and bias parameters are set by glConvolutionParameterEXT using the GL_CONVOLUTION_2D_EXT target and the names GL_CONVOLUTION_FILTER_SCALE_EXT and GL_CONVOLUTION_FILTER_BIAS_EXT. The parameters themselves are vectors of four values that are applied to red, green, blue, and alpha, in that order.) The R, G, B, and A values are not clamped to [0,1] at any time during this process.

Each pixel is then converted to the internal format specified by internalformat. This conversion maps the component values of the pixel (R, G, B, and A) to the values included in the internal format (red, green, blue, alpha, luminance, and intensity). The mapping is as follows:

internalformat	Red	Green	Blue	Alpha	Luminance	Intensity
GL_ALPHA	-	-	-	A	-	-
GL_LUMINANCE	-	-	-	-	R	-
GL_LUMINANCE_ALPHA	-	-	-	A	R	-
GL_INTENSITY	-	-	-	-	-	R
GL_RGB	R	G	B	-	-	-
GL_RGBA	R	G	B	A	-	-

The red, green, blue, alpha, luminance, and intensity components of the resulting pixels are stored in floating-point rather than integer format. They form a two-dimensional filter kernel image indexed with coordinate i and j such that i starts at 0 and increases from left to right, and j starts at 0 and increases from bottom to top. Kernel location (i, j) is derived from the n^th pixel, where n is i + j * width.

Note that after a convolution is performed, the resulting color components are also scaled by their corresponding GL_POST_CONVOLUTION_c_SCALE_EXT parameters and biased by their corresponding GL_POST_CONVOLUTION_c_BIAS_EXT parameters (where c takes on the values RED, GREEN, BLUE, and ALPHA). These parameters are set by glPixelTransfer.

EXTENSIONS

GL_EXT_422_pixels

GL_422_EXT, GL_422_REV_EXT, GL_422_AVERAGE_EXT, and GL_422_REV_AVERAGE_EXT are part of the EXT_422_pixels extension.

GL_EXT_bgra

GL_BGR_EXT and GL_BGRA_EXT are part of the EXT_bgra extension.

GL_EXT_convolution

glConvolutionFilter2DEXT, GL_CONVOLUTION_2D_EXT, GL_CONVOLUTION_FILTER_SCALE_EXT, and GL_CONVOLUTION_FILTER_BIAS_EXT are part of the EXT_convolution extension.

GL_EXT_packed_pixels

GL_UNSIGNED_BYTE_3_3_2_EXT, GL_UNSIGNED_BYTE_2_3_3_REV_EXT, GL_UNSIGNED_SHORT_5_6_5_EXT, GL_UNSIGNED_SHORT_5_6_5_REV_EXT, GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_4_4_4_4_REV_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT, GL_UNSIGNED_SHORT_1_5_5_5_REV_EXT, GL_UNSIGNED_INT_8_8_8_8_EXT, GL_UNSIGNED_INT_8_8_8_8_REV_EXT, GL_UNSIGNED_INT_10_10_10_2_EXT, and GL_UNSIGNED_INT_2_10_10_10_REV_EXT are part of the EXT_packed_pixels extension.

ERRORS

GL_INVALID_ENUM is generated if internalformat is not one of the allowable values.

GL_INVALID_VALUE is generated if width is less than zero or greater than the maximum supported value. This value may be queried with glGetConvolutionParameterEXT using target GL_CONVOLUTION_2D_EXT and name GL_MAX_CONVOLUTION_WIDTH_EXT.

GL_INVALID_VALUE is generated if height is less than zero or greater than the maximum supported value. This value may be queried with glGetConvolutionParameterEXT using target GL_CONVOLUTION_2D_EXT and name GL_MAX_CONVOLUTION_HEIGHT_EXT.

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 glConvolutionFilter2DEXT is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

SEE ALSO