GLCONVOLUTIONFILTER2D(3G) GLCONVOLUTIONFILTER2D(3G)
NAME
glConvolutionFilter2D - define a two-dimensional convolution filter
C SPECIFICATION
void glConvolutionFilter2D( GLenum target,
GLenum internalformat,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
const GLvoid *image )
PARAMETERS
target Must be GL_CONVOLUTION_2D.
internalformat The internal of the convolution filter kernel. The allowable values are GL_ALPHA,
GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16, GL_LUMINANCE, GL_LUMINANCE4,
GL_LUMINANCE8, GL_LUMINANCE12, GL_LUMINANCE16, GL_LUMINANCE_ALPHA,
GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8,
GL_LUMINANCE12_ALPHA4, GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16, GL_INTENSITY,
GL_INTENSITY4, GL_INTENSITY8, GL_INTENSITY12, GL_INTENSITY16, GL_R3_G3_B2, GL_RGB,
GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12, GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4,
GL_RGB5_A1, GL_RGBA8, GL_RGB10_A2, GL_RGBA12, or GL_RGBA16.
width The width of the pixel array referenced by image.
height The height of the pixel array referenced by image.
format The of the pixel data in image. The allowable values are GL_RED, GL_GREEN, GL_BLUE,
GL_ALPHA, GL_RGB, GL_BGR, GL_RGBA, GL_BGRA, GL_LUMINANCE, and GL_LUMINANCE_ALPHA.
type The type of the pixel data in 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 a two-dimensional array of pixel data that is processed to build the con-volution convolution
volution filter kernel.
DESCRIPTION
glConvolutionFilter2D builds a two-dimensional convolution filter kernel from an array of pixels.
The pixel array specified by width, height, format, type, and image is extracted from memory and pro-cessed processed
cessed just as if glDrawPixels were called, but processing stops after the final expansion to RGBA is
completed.
The R, G, B, and A components of each pixel are next scaled by the four 2D
GL_CONVOLUTION_FILTER_SCALE parameters and biased by the four 2D GL_CONVOLUTION_FILTER_BIAS parame-ters. parameters.
ters. (The scale and bias parameters are set by glConvolutionParameter using the GL_CONVOLUTION_2D
target and the names GL_CONVOLUTION_FILTER_SCALE and GL_CONVOLUTION_FILTER_BIAS. 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 specified by internalformat. This conversion simply
maps the component values of the pixel (R, G, B, and A) to the values included in the internal (red,
green, blue, alpha, luminance, and intensity). The mapping is as follows:
Internal Format Channel mapping
GL_ALPHA A=Alpha
GL_LUMINANCE R=Luminance
GL_LUMINANCE_ALPHA A=Alpha, R=Luminance
GL_INTENSITY R=Intensity
GL_RGB R=Red, G=Green, B=Blue
GL_RGBA R=Red, G=Green, B=Blue, A=Alpha
The red, green, blue, alpha, luminance, and/or intensity components of the resulting pixels are
stored in floating-point rather than integer They form a two-dimensional filter kernel image indexed
with coordinates i and j such that i starts at zero and increases from left to right, and j starts at
zero and increases from bottom to top. Kernel location i,j is derived from the Nth 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 parameters and biased by their corresponding
GL_POST_CONVOLUTION_c_BIAS parameters (where c takes on the values RED, GREEN, BLUE, and ALPHA).
These parameters are set by glPixelTransfer.
NOTES
glConvolutionFilter2D 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_CONVOLUTION_2D.
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 glGetConvolutionParameter using target GL_CONVOLUTION_2D and name
GL_MAX_CONVOLUTION_WIDTH.
GL_INVALID_VALUE is generated if height is less than zero or greater than the maximum supported
value. This value may be queried with glGetConvolutionParameter using target GL_CONVOLUTION_2D and
name GL_MAX_CONVOLUTION_HEIGHT.
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 glConvolutionFilter2D is executed between the execution of
glBegin and the corresponding execution of glEnd.
GL_INVALID_OPERATION is generated if height 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 height 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, glGetConvolutionFilter
SEE ALSO
glConvolutionFilter1D(3G), glSeparableFilter2D(3G), glConvolutionParameter(3G), glPixelTransfer(3G)
GLCONVOLUTIONFILTER2D(3G)
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