Merging tiles together

montage -background transparent -geometry 210x244+0+0 -tile 16x17 *.png atlas.png

Merging animation sprites

montage -background transparent -tile 8x1 *.png atlas.png

Splitting texture atlas tiles

convert pickups_copy.png -crop 3x2-0-0@ +repage +adjoin tile-%d.png

Resize image

convert heart.png -resize 20% heart_small.png

convert heart.png -resize 64x64 heart_small.png The image is not stretched anyway and is resized to the minimum edge specified. In case of a 256x256 image, -resize 64x128 will result in a 64x64 image