glConvolutionFilter2D

glConvolutionFilter2D: man2/glConvolutionFilter2D.xml

glConvolutionFilter2D builds a two-dimensional convolution filter kernel from an array of pixels. The pixel array specified by width, height, format, type, and data is extracted from memory and processed just as if glDrawPixels were called, 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, data is treated as a byte offset into the buffer object's data store. 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 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 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 and such that starts at zero and increases from left to right, and starts at zero and increases from bottom to top. Kernel location is derived from the th pixel, where is + * 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 takes on the values RED, GREEN, BLUE, and ALPHA ). These parameters are set by glPixelTransfer.

glConvolutionFilter2D is present only if ARB_imaging is returned when glGetString is called with an argument of GL_EXTENSIONS.