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I'm trying to do something very simple but somehow can't manage to do it.

I have an PNG with transparent areas.

How to add a background layer filled with some RGBA color such as rgba(255,0,0,128)?

I'm using imagemagick version 6 in its command line form.

This would be the PNG image for example: enter image description here

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2 Answers 2

Reset to default
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You can do that in ImageMagick by flattening the image against a color.

convert sayduck.png -background "rgba(255,0,0,0.5)" -flatten result.png


enter image description here

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3 Comments

Hum actually, not really. If you see, now the background isn't rgba(255,0,0,128) but rgba(255,0,0,255). We lost the transparency of it.
Same mistake as emcconville - used your values without thinking about how alpha is specified in ImageMagick. Need to change alpha in rgba from 128 to 0.5. Corrected now.
thanks ... I had it all along, did not realise the alpha chanel
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First thing I can think of is to draw the color and composite under the image.

convert input.png \( +clone -fill 'rgba(255,0,0,0.5)' -draw 'color 0,0 reset' \) +swap -composite output.png

output.png

Although I'm sure there's quicker ways.

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Same than the answer bellow: If you see, now the background isn't rgba(255,0,0,128) but rgba(255,0,0,255). We lost the transparency of it.

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