fglConvolutionFilter2D(3G) OpenGL Reference fglConvolutionFilter2D(3G)NAME
fglConvolutionFilter2D - define a two-dimensional convolution filter
FORTRAN SPECIFICATION
SUBROUTINE fglConvolutionFilter2D( INTEGER*4 target,
INTEGER*4 internalformat,
INTEGER*4 width,
INTEGER*4 height,
INTEGER*4 format,
INTEGER*4 type,
CHARACTER*8 image )
PARAMETERS
target Must be GL_CONVOLUTION_2D.
internalformat The internal format 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 format 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_ABGR_EXT, 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.
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fglConvolutionFilter2D(3G) OpenGL Reference fglConvolutionFilter2D(3G)
image Pointer to a two-dimensional array of pixel data that is
processed to build the convolution filter kernel.
DESCRIPTION
fglConvolutionFilter2D 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 processed just as if fglDrawPixels 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 parameters. (The scale and bias parameters
are set by fglConvolutionParameter 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 format 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 format
(red, green, blue, alpha, luminance, and intensity). The mapping is as
follows:
_______________________________________________________________________
Internal Format 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/or 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
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 fglPixelTransfer.
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fglConvolutionFilter2D(3G) OpenGL Reference fglConvolutionFilter2D(3G)NOTES
fglConvolutionFilter2D is present only if GL_ARB_imaging is returned when
fglGetString is called with an argument of GL_EXTENSIONS.
GL_ABGR_EXT is valid only if the EXT_abgr extension is supported.
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
fglGetConvolutionParameter 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
fglGetConvolutionParameter 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 fglConvolutionFilter2D is executed
between the execution of fglBegin and the corresponding execution of
fglEnd.
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 not GL_RGBA, GL_BGRA or GL_ABGR_EXT.
ASSOCIATED GETS
fglGetConvolutionParameter, fglGetConvolutionFilter
SEE ALSO
fglConvolutionFilter1D, fglSeparableFilter2D, fglConvolutionParameter,
fglPixelTransfer
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