How can I rotate a transparent png by 45 degrees using imagemagick and keep the new image transparent?

Question

I have a 16x16 transparent png and I did

convert -rotate -45 a.png b.png

This rotated it and created a new image b.png which is of size 22x22 and which when I use against a background shows the original image (16x16) rotated with the underlying background but the new filling that came about shows up with a white background.

How is it possible to have the new filling too be transparent?

If that is not possible, than how can I have all the background of the new image be one color?

Ingvi Gautsson · Answer 1 · 2013-01-07T01:25:21.753

15

Use the -background option to specify a transparent color with alpha set to zero:

convert -background 'rgba(0,0,0,0)' -rotate 45 a.png b.png

edited Jan 07 '13 at 01:25

answered Apr 03 '11 at 07:39

Ingvi Gautsson

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It should be `convert -background 'rgba(0,0,0,0)' -rotate 45 a.png b.png` – Crazenezz Dec 19 '12 at 12:16

score 9 · Answer 2 · edited Jul 14 '12 at 19:15

9

You can also use these options:

  -background none

edited Jul 14 '12 at 19:15

reuben

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answered Jul 10 '12 at 01:59

uFarooq

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FYI: Depending on how ImageMagick is installed an configured, `-background none' might result in an error like `convert: unable to access configure file `colors.xml' @ warning/configure.c/GetConfigureOptions/589.`. This happens when ImageMagick can't find a config file because of where things are installed. If you run into that, you can use `-background 'rgba(0,0,0,0)'` instead. – Alan W. Smith Feb 12 '13 at 03:07

score 3 · Answer 3 · edited Feb 12 '13 at 03:10

3

I was also having the same issue, however I was using the command like so:

convert a.png -rotate 45 -background transparent b.png

It needed to be:

convert -rotate 45 -background transparent a.png b.png

So, this actually helped a little, thanks :)

edited Feb 12 '13 at 03:10

Alan W. Smith

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answered Jul 01 '11 at 03:38

nak

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score 1 · Answer 4 · edited Feb 12 '13 at 03:09

1

convert -rotate 66 -background none c:\input.png c:\output.png

works well for me

edited Feb 12 '13 at 03:09

Alan W. Smith

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answered Aug 29 '12 at 09:42

sukinsan

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score 0 · Answer 5 · edited Jan 21 '15 at 10:26

0

I used C# to rotate it

using (MagickImage mimg = new MagickImage(path))
{
  mimg.BackgroundColor = MagickColor.Transparent;
  mimg.Alpha(AlphaOption.Background);
  mimg.AlphaColor = new MagickColor(System.Drawing.Color.White);
  mimg.FillColor = new MagickColor(255, 255, 255, 0);
  mimg.Rotate(degree);                    
}

edited Jan 21 '15 at 10:26

dlemstra

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answered Jan 21 '15 at 08:29

Mohammad Gabr

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I don't think you need the Alpha, AlphaColor and FillColor calls in it. You just need to make sure to set BackgroundColor to transparent *before* rotating. – caiosm1005 Dec 23 '21 at 12:49

How can I rotate a transparent png by 45 degrees using imagemagick and keep the new image transparent?

5 Answers5