pngtopnm: reading a 640w x 300h image, 8 bits
pngtopnm: truecolor+alpha, not interlaced, base filter
pngtopnm: background {index, gray, red, green, blue} = {0, 0, 0, 0, 0}
pngtopnm: tRNS chunk (transparency): not present
pngtopnm: gAMA chunk (image gamma): not present
pngtopnm: sBIT chunk: present
pngtopnm: cHRM chunk: not present
pngtopnm: PLTE chunk: not present
pngtopnm: bKGD chunk: not present
pngtopnm: hIST chunk: not present
pngtopnm: pHYs chunk: present
pngtopnm: oFFs chunk: not present
pngtopnm: tIME chunk: not present
pngtopnm: pCAL chunk: not present
pngtopnm: sRGB chunk: not present
pngtopnm: writing a PPM file (maxval=255)
pnmremap: 16 colors found in colormap
pnmremap: 0 pixels not matched in color map
192000 pixels, 74128 bytes, (22.78% compression)
#000000=0
#143965=1
#1c3d6d=2
#14498e=3
#204579=4
#1c4982=5
#314d75=6
#ffffff=7
#205192=8
#28518e=9
#355d9a=10
#456da2=11
#5579aa=12
#61799a=13
#96aabe=14
#cad7e3=15
pnmtopng: reading a PPM file (maxval=255)
pnmtopng: Finding colors in input image...
pnmtopng: 16 colors found
pnmtopng: reading ordered palette (colormap)...
pnmtopng: 16 colors found
pnmtopng: PNG palette has 16 entries, 0 of them non-opaque
pnmtopng: Writing 4-bit color indexes
pnmtopng: writing a 4-bit palette file