From: Tim Hunter <rmagick@...>
Date: 2008-02-07T00:27:29+09:00
Subject: Re: question about transparent image RMAGIK

Shawn Bright wrote:
> Hello there all,
> i have a simple function to draw an image, but i cannot for the life
> of me figgure out from the docs how to make it about 20% transparent.
> 
>  def circle_image(zoom)
>     site = self.site
>      zoomhash = {13 => 0.5, 14 => 1, 15 => 2, 16 => 4}
>     r = (self.radius.to_f * zoomhash[zoom.to_i].to_f)
>     canvas = Magick::Image.new((2 * r), (2*r),
> Magick::HatchFill.new('transparent', 'transparent'))
>     gc = Magick::Draw.new
>     # for the outside perimeter of the circle
>     gc.stroke('black')
>     gc.stroke_width(1)
>     # fill in the inside
>     color = KeyWord.stat_description(site.status_sensor.last_value)[1]
>     gc.fill(color)
>     gc.circle(r, r, 0, r)
>     image = gc.draw(canvas)
>     canvas.write("public/images/tmp/#{site.id}.png")
>   end
> 
> please help, thanks
> 
> shawn

Do you want to make the entire image 20% transparent? Use the 
Image#opacity= attribute 
[http://studio.imagemagick.org/RMagick/doc/imageattrs.html#opacity].

Do you want to make the drawing 20% transparent so that the drawn-upon 
image shows through? See the Draw#stroke_opacity 
[http://studio.imagemagick.org/RMagick/doc/draw.html#stroke_opacity] and 
Draw#fill_opacity 
[http://studio.imagemagick.org/RMagick/doc/draw.html#fill_opacity] 
methods.

Also check out the example drawing here 
[http://studio.imagemagick.org/RMagick/doc/usage.html#drawing_on].
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