From: Tim Hunter <TimHunter@...>
Date: 2009-08-10T01:19:19+09:00
Subject: Re: Imagemagick, Rmagick hsla problem

Justin Bl wrote:
> Tim Hunter wrote:
>> Justin Bl wrote:
>>> Ruby version: 1.8.6
>>> ImageMagick Version: 6.5.3 Q8
>>> Rmagick Version: rmagick-2.10.0-x86-mswin32
>>> OS: Windows Vista
>> I don't think the problem is with the from_hsla method. This produces a
>> nice sorta lime-green 200x200 image for me. Why don't you post a
>> complete script that reproduces the problem?
>>
>> irb(main):001:0> p = Magick::Pixel.from_hsla(80, 100, 50, 1)
>> => red=170, green=255, blue=0, opacity=0
>> irb(main):002:0> img = Magick::Image.new(200,200) {
>> self.background_color = p}
>> =>   200x200 DirectClass 8-bit
>> irb(main):003:0> img.display
>> =>   200x200 DirectClass 8-bit
> 
> Tim,
> Full source code is below:
> 
>   require 'rubygems'
>   require 'rvg/rvg'
>   include Magick
> 
> class MyImage
> def initialize (job_id, width, height)
> 
> @job_id = job_id.to_s;
> @width = width.to_i;
> @height = height.to_i;
> @canvas = Magick::Image.new(@width, @height)
> #@canvas.colorspace = HSLColorspace
> @canvas.background_color = Magick::Pixel.from_hsla(80, 100, 50, 1)
> #it will make the pixel but it will not make it the right color
> end
> def draw ()
> # choose random color and put it in a pixel
> #@canvas.each_pixel {|pixel, c, r|
>   #ind = rand(5)
>   #pixel = $colors[ind]
> #}
> #@canvas.pixel_color(x, y[, new_color]) -> pixel
> 
> end
> def finalize (type="gif")
> @canvas.write("#{@job_id}.#{type}")
> end
> end
> 
> x = 500
> y = 500
> increm = 360/5
> 
> $colors = Array.new
> $colors = [
> [0,100,50,1],
> [72,100,50,1],
> [144,100,50,1],
> [216,100,50,1],
> [288,100,50,1]
> ]
> # initial array is just the h s l a values
> $colors = $colors.map { |xx| Magick::Pixel.from_hsla(xx[0], xx[1], 
> xx[2], x[3]) }
> # convert it to array of pixels
> puts $colors[0].class
> 
> img = MyImage.new("hsl_test", x, y)
> img.draw()
> img.finalize('png')

The color of a new image is set when the image is created. Do this:

@canvas = Magick::Image.new(@width, @height) do
    self.background_color = Magick::Pixel.from_hsla(80, 100, 50, 1)
end

Setting the background_color attribute *after* creating the image only 
changes the value of the background_color attribute. It doesn't actually 
change the color of the image.


-- 
MagickWand for Ruby - http://magickwand.rubyforge.org/