incorrect size on pdftoppm
Using the attached file with following command (on poppler 0.89.0), the png file produced is 257x256, instead of 256x256.
pdftoppm -scale-dimension-before-rotation -r 200 pmc6187247.pdf -f 1 -l 13 -scale-to-x 256 -scale-to-y 256 -singlefile -png > scaled.png