From: Joe Van Dyk <joevandyk@...>
Date: 2005-08-27T07:53:22+09:00
Subject: Re: rmagick question

On 8/26/05, Joe Van Dyk <joevandyk@gmail.com> wrote:
> On 8/26/05, Brian Schr�der <ruby.brian@gmail.com> wrote:
> > On 26/08/05, Joe Van Dyk <joevandyk@gmail.com> wrote:
> > > I'm trying to set the pixels of an image:
> > >
> > > require 'RMagick'
> > >
> > > width = 512
> > > height = 256
> > >
> > > image = Magick::Image.new width, height
> > >
> > > width.times do |x|
> > >   height.times do |y|
> > >     pixel = Magick::Pixel.new rand(256), rand(256), rand(256)
> > >     image.pixel_color x, y, pixel
> > >   end
> > > end
> > >
> > > image.write ARGV.shift
> > >
> > > But the resulting image is all black.  Why?
> > >
> > >
> >
> > Use Magick::MaxRGB+1 instead of 256. RGB Values range from 0...2**16.
> > And be shure to check out the View funktionality.
> 
> The following behavior is confusing to me.
> 
>         p rgb
>         pixel = Magick::Pixel.new(*rgb)
>         image.pixel_color(e, n, pixel)
>         p image.pixel_color(e, n)
>         p pixel
> 
> This returns the following output:
> 
> [2, 0, 0]
> red=65535, green=65535, blue=65535, opacity=0
> red=2, green=0, blue=0, opacity=0
> 
> I create a new pixel, I set the image pixel to be that color, but the
> image pixel is still a different color.

Aha!  On an image with dimensions (say) 200x200, I was trying to set
image.pixel_color(0, 200, pixel).  That's outside the image... I
really wanted to set image.pixel_color(0, 199, pixel).