join multiple png images
Solution 1:
ImageMagick can do this:
convert 1.png 2.png -append result.png
Alignment options can be (optionally) specified using the -gravity switch,
-
-gravity Eastalign the right edges -
-gravity Westalign the left edges -
-gravity centeralign the centers
Note: using +append instead of -append will stitch the images together horizontally, i.e. side-by-side rather than one above the other.