# man > pgmkernel(1) > **TLDR:** Generate a convolution kernel to be used with `pnmconvol`. > - Generate a convolution kernel: `pgmkernel {{width}} {{height}} > {{path/to/output.pgm}}` - Generate a quadratic convolution kernel: `pgmkernel {{size}} > {{path/to/output.pgm}}` - Specify the weight of the center in the generated kernel: `pgmkernel {{-w|-weight}} {{value}} {{width}} {{height}} > {{path/to/output.pgm}}` *Source: tldr-pages* --- [pgmkernel(1)](https://www.chedong.com/phpMan.php/man/pgmkernel/1/markdown) General Commands Manual [pgmkernel(1)](https://www.chedong.com/phpMan.php/man/pgmkernel/1/markdown) ## NAME pgmkernel - generate a convolution kernel ## SYNOPSIS **pgmkernel** [ **-weight** _w_ ] _width_ [ _height_ ] ## DESCRIPTION Generates a portable graymap array of size _width_ x _height_ (or _width_ x _width_ if _height_ is not specified) to be used as a convolution file by **pnmconvol**. The data in the convolution array K are computed according to the formula: K(i,j) = 1 / ( 1 + w * sqrt((i-width/2)^2 + (j-height/2)^2)) where _w_ is a coefficient specified via the _-weight_ flag, and _width_ and _height_ are the X and Y filter sizes. The output PGM file is always written out in ASCII format. ## OPTIONS The optional _-weight_ flag should be a real number greater than -1. The default value is 6.0. ## BUGS The computation time is proportional to _width_ * _height_. This increases rapidly with the in‐ crease of the kernel size. A better approach could be using a FFT in these cases. ## SEE ALSO [pnmconvol(1)](https://www.chedong.com/phpMan.php/man/pnmconvol/1/markdown), [pnmsmooth(1)](https://www.chedong.com/phpMan.php/man/pnmsmooth/1/markdown) ## AUTHOR Alberto Accomazzi (). 10 December 1992 [pgmkernel(1)](https://www.chedong.com/phpMan.php/man/pgmkernel/1/markdown)