This is a text file usually called
Its header is extremely simple: It consists of only one number which is the maximal (= equatorial) diagonal half distance of two pixels in degrees. This value is used as the radius for the milky way pixels. Of course it must be the minimal radius for which there are no gaps between the pixels.
What follows are the Milky Way pixels themselves. Each consists of tree entries, separated by white space:
0.212 11.885 0.259 1 11.962 0.295 5 11.974 0.298 5 17.982 -26.999 136 17.982 -27.299 158 17.982 -27.599 169 17.982 -27.899 199 17.981 -28.199 235
I used the All-Sky Milky Way Panorama by Axel Mellinger. His bitmap with the two hemispheres in equidistant azimuthal projection was greyscaled and smoothed with the Gimp, and then transformed to PP3's format with a small hand-written C program.