MirOS Manual: glSeparableFilter2D(3)


GLSEPARABLEFILTER2D(3UNIX Programmer's ManGLSEPARABLEFILTER2D(3G)

NAME

     glSeparableFilter2D - define a separable two-dimensional
     convolution filter

C SPECIFICATION

     void glSeparableFilter2D( GLenum target,
                               GLenum internalformat,
                               GLsizei width,
                               GLsizei height,
                               GLenum format,
                               GLenum type,
                               const GLvoid *row,
                               const GLvoid *column )

PARAMETERS

     target          Must be GL_SEPARABLE_2D.

     internalformat  The internal  of the convolution filter ker-
                     nel. 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 number of elements in the pixel array
                     referenced by row. (This is the width of the
                     separable filter kernel.)

     height          The number of elements in the pixel array
                     referenced by column. (This is the height of
                     the separable filter kernel.)

     format          The  of the pixel data in row and column.
                     The allowable values are GL_RED, GL_GREEN,
                     GL_BLUE, GL_ALPHA, GL_RGB, GL_BGR, GL_RGBA,
                     GL_BGRA, GL_INTENSITY, GL_LUMINANCE, and
                     GL_LUMINANCE_ALPHA.

     type            The type of the pixel data in row and
                     column. Symbolic constants GL_UNSIGNED_BYTE,

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GLSEPARABLEFILTER2D(3UNIX Programmer's ManGLSEPARABLEFILTER2D(3G)

                     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.

     row             Pointer to a one-dimensional array of pixel
                     data that is processed to build the row
                     filter kernel.

     column          Pointer to a one-dimensional array of pixel
                     data that is processed to build the column
                     filter kernel.

DESCRIPTION

     glSeparableFilter2D builds a two-dimensional separable con-
     volution filter kernel from two arrays of pixels.

     The pixel arrays specified by (width, format, type, row) and
     (height, format, type, column) are processed just as if they
     had been passed to glDrawPixels, but processing stops after
     the final expansion to RGBA is completed.

     Next, the R, G, B, and A components of all pixels in both
     arrays are scaled by the four separable 2D
     GL_CONVOLUTION_FILTER_SCALE parameters and biased by the
     four separable 2D GL_CONVOLUTION_FILTER_BIAS parameters.
     (The scale and bias parameters are set by
     glConvolutionParameter using the GL_SEPARABLE_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:

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GLSEPARABLEFILTER2D(3UNIX Programmer's ManGLSEPARABLEFILTER2D(3G)

_______________________________________________________________________

Internal Format Red Green Blue Alpha Luminance Intensity

_______________________________________________________________________

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 They form two one-dimensional
     filter kernel images. The row image is indexed by coordinate
     i starting at zero and increasing from left to right. Each
     location in the row image is derived from element i of row.
     The column image is indexed by coordinate j starting at zero
     and increasing from bottom to top. Each location in the
     column image is derived from element j of column.

     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

     glSeparableFilter2D 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_SEPARABLE_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_SEPARABLE_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_SEPARABLE_2D and name GL_MAX_CONVOLUTION_HEIGHT.

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

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GLSEPARABLEFILTER2D(3UNIX Programmer's ManGLSEPARABLEFILTER2D(3G)

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

     GL_INVALID_OPERATION is generated if glSeparableFilter2D 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, glGetSeparableFilter

SEE ALSO

     glConvolutionFilter1D(3G), glConvolutionFilter2D(3G),
     glConvolutionParameter(3G), glPixelTransfer(3G)

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