# pnmconvol > Convolute a PNM image. > More information: . - Convolve a PNM image with the specified convolution matrix: `pnmconvol -matrix=-1,3,-1 {{path/to/image.pnm}} > {{path/to/output.pnm}}` - Convolve a PNM image with the convolution matrix in the specified files, one for each layer in the input image: `pnmconvol -matrixfile {{path/to/matrix1,path/to/matrix2,...}} {{path/to/image.pnm}} > {{path/to/output.pnm}}` - Convolve a PNM image with the convolution matrix in the specified PNM file: `pnmconvol {{path/to/matrix.pnm}} {{path/to/image.pnm}} > {{path/to/output.pnm}}` - Normalize the weights in the convolution matrix such that they add up to one: `pnmconvol -matrix=-1,3,-1 -normalize {{path/to/image.pnm}} > {{path/to/output.pnm}}`