glSeparableFilter2D

glSeparableFilter2D: man2/glSeparableFilter2D.xml

glSeparableFilter2D builds a two-dimensional separable convolution 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. If a non-zero named buffer object is bound to the GL_PIXEL_UNPACK_BUFFER target (see glBindBuffer ) while a convolution filter is specified, row and column are treated as byte offsets into the buffer object's data store. 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 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_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 two one-dimensional filter kernel images. The row image is indexed by coordinate starting at zero and increasing from left to right. Each location in the row image is derived from element of row. The column image is indexed by coordinate starting at zero and increasing from bottom to top. Each location in the column image is derived from element 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 takes on the values RED, GREEN, BLUE, and ALPHA ). These parameters are set by glPixelTransfer.

glSeparableFilter2D is present only if ARB_imaging is returned when glGetString is called with an argument of GL_EXTENSIONS.