pnmmercator

Apply Mercator projection

$ pnmmercator [input.pnm] > [output.pnm]

$ pnmmercator -inverse [input.pnm] > [output.pnm]

pnmmercator [options] [file]

pnmmercator converts PNM images between equirectangular (plate carrée) and Mercator map projections. The input image is treated as a map where rows correspond to latitude lines and columns to longitude lines.
The forward transform converts equirectangular to Mercator projection, stretching areas near the poles. The -inverse option reverses this, converting from Mercator back to equirectangular. Part of the Netpbm toolkit.

-inverse

Convert from Mercator to equirectangular.

pamscale(1), pnmshear(1)