convert input.png -extent 100x100 -gravity center -background white output.png If the input is 50x50 the surrounding background is white. Can I somehow set this to transparent without declaring any color within input as transparent?
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2 Answers
Use this instead:
convert \ input.png \ -background none \ -gravity center \ -extent 100x100 \ output.png Note well: The order of the parameters is significant! (To convince yourself, just put -background none at the end of the parameters instead of the start...)
Updated: Thanks to @jesmith who noticed that the commandline I originally provided does no longer work as intended. More recent versions of convert additionally require that the -gravity center is called before -extent 100x100. (This was one of the changes introduced to one ImageMagick's most recent versions [at the time of originally writing this answer]).
2 Comments
Joshua Smith
Indeed the order is important, and you got it wrong! You need to put -gravity before -extent, or it will have no effect. Try -gravity SouthEast to see what I mean.
Kurt Pfeifle
@noɥʇʎPʎzɐɹC: Thx -- fixed.
Kurt's note is ironically spot on, order matters greatly. Kurt's command results in gravity not being applied to the extent, so the transparent 'border' will all be to the bottom and/or right of the image.
Moving gravity before extent will correctly create equal transparent 'borders' on all applicable sides.
convert input.jpg -background none -gravity Center -extent 100x50 output.png
1 Comment
Kurt Pfeifle
+1 and thanks for your additional answer pointing out the now required command line order for
-gravity center. I hadn't seen it, nor @jesmith's comment earlier, though he had pointed it out already in May '13.