Legacy ImageMagick Discussions Archive

Hello,

I have an image with transparency. And I want to save it as JPEG. I am using C. Everything works fine, except that transparent image places are black in output image. And I could not figure out how to change it, lets say to white.

Tried this:

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PixelWand *myPixelWand = NewPixelWand();
		PixelSetColor(myPixelWand,"rgba(255,255,255,255)");
		PixelSetOpacity(myPixelWand, 1.0); // tried 0.0 and 1.0
		MagickSetImageMatteColor(saveWand, myPixelWand);
		DestroyPixelWand(myPixelWand);

Does not work.

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PixelWand *myPixelWand = NewPixelWand();
		PixelSetColor(myPixelWand,"rgba(255,255,255,255)");
		PixelSetOpacity(myPixelWand, 1.0); // tried 0.0 and 1.0
		MagickSetImageBackgroundColor(saveWand, myPixelWand);
		DestroyPixelWand(myPixelWand);

Does not work also.

By the way: MagickGetImageMatte(saveWand) returns MagickTrue;

Any help would be very appreciate.

p.s.using ImageMagick 6.3.4

Here are files I am using:

source: http://img250.imageshack.us/img250/1439 ... e01rj1.png

result: http://img235.imageshack.us/img235/1918 ... e08vv4.jpg

Black area of result image should be white (in my case).

This will do it:

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convert input.png ( +clone -channel a -separate -negate ) +swap -composite output.jpg

It extracts the matte channel, negates it so that what was transparent is now white and then composites the original png over the top.
If you want a colour other than white, you'd have to replace the white in the negated matte with something else. I'm not sure how to do that though (yet).
Pete

Actually the simplest way is to -flatten the image before saving to JPG.

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convert image.png  -background white -flatten image.jpg

Of course! Thanks Anthony.

Pete

Legacy ImageMagick Discussions Archive

Allways black transparency in JPEG images

Allways black transparency in JPEG images

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Re: Allways black transparency in JPEG images

Re: Allways black transparency in JPEG images