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I'm trying to rotate an image before composing it ontop of another, using RMagick with ruby. I can compose the overlaid image but when I try to rotate the image parts of the background are removed, like so...

enter image description here

Im not sure which CompositeOperator I should be using, or if this is the wrong approach all together?

image = Magick::Image.read("img.jpg").first         
overlay = Magick::Image.read("./overlay.png").first
overlay.rotate!(9)
image.composite!(overlay, 100, 50, Magick::OverCompositeOp)
image.to_blob
michael
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2 Answers2

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Before rotating set your background to none:

overlay.background_color = "none"

Other possible methods to use after the rotation:

img.transparent_chroma(low, high, opacity=TransparentOpacity, invert=false)
img.transparent(color, opacity=TransparentOpacity)

so in your case:

overlay.transparent!("white")
Sean Vikoren
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0

you need to set the image transparency with the :opacity parameter

http://alternateidea.com/blog/articles/2005/9/19/custom-image-overlays-with-rmagick

http://www.ruby-forum.com/topic/119556

http://www.rhinocerus.net/forum/lang-ruby/63271-transparent-image-using-rmagick.html

RMagick: Convert CMYK EPS to RGB PNG maintaining transparent background

Community
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Tilo
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