RMagick Help

ruby-talk
1

Hello,

I finally got RMagick working on my OS X machine and I'm trying to use it to accomplish some things that I was previously doing with ImageMagick through the %x mechanism. Specifically, I want to read in an image and spit out a list of individual rgb values. This seems easy enough:

@sourceimage=Image::read(@filename).first
@sourceimage.get_pixels(0, 0, @sourceimage.columns, @sourceimage.rows)

What I really want, though, is 8-bit color values (0-255) rather than the 16-bit values (0-65535) that get spit out. Does anyone know how to go about this? I feel like it must be possible, but I've been back and forth through the documentation and can't figure it out. Any help would be greatly appreciated.

Thanks,

miek

2

I happen to be doing something similar right now. Here's some code that
should show one way to do it... This prints out the 8-bit pixel values
for any image(s) passed on the command-line. (Just chopping off the low
order byte...)

Example: ruby foo.rb images/*.png

- --------------------------------

require 'RMagick'

imageList = Magick::ImageList.new(*ARGV)

imageList.each do |image|
  puts "Bits Per Pixel: #{image.depth}"

  view = image.view(0, 0, image.columns, image.rows)

  0.upto(view.width) do |x|
    0.upto(view.height) do |y|
      red = view[y].red >> 8
      green = view[y].green >> 8
      blue = view[y].blue >> 8

      puts "(#{red}, #{green}, #{blue})"
    end
  end

end

- -------------------------------

Peace,
Jeff

Michael Leonard wrote:

ยทยทยท

Hello,

I finally got RMagick working on my OS X machine and I'm trying to use
it to accomplish some things that I was previously doing with
ImageMagick through the %x mechanism. Specifically, I want to read in an
image and spit out a list of individual rgb values. This seems easy enough:

@sourceimage=Image::read(@filename).first
@sourceimage.get_pixels(0, 0, @sourceimage.columns, @sourceimage.rows)

What I really want, though, is 8-bit color values (0-255) rather than
the 16-bit values (0-65535) that get spit out. Does anyone know how to
go about this? I feel like it must be possible, but I've been back and
forth through the documentation and can't figure it out. Any help would
be greatly appreciated.

Thanks,

miek

3

For what it's worth:

If you don't mind recompiling ImageMagick, you can set the option
--with-quantum-depth=8. It's recommended to just use the 8 bit
processing if you're not doing work that needs the extra depth. It
has the added benefit of making your processing faster.

- Dimitri

4

That worked perfectly. Thank you very much. I was unaware of the ">>"
operator.