itsme213 wrote:
> I am using RMagick to do multi-stage processing of some images.
> 
> Can I have two different rules to process .PNG files in two different
> directories?
> 
> rule stage_0/*.png => source/*.png do |t|
>    make_0 t.source, t.name
> end
> 
> rule stage_1/*.png => stage_0/*.png do |t|
>    make_1 t.source, t.name
> end
> 
> 
> I can't seem to get this to work, and don't know if it is supposed to.

It will work.  The attached Rakefile will demonstrate the principle. 
Basically, if you want your rules to trigger on something other than 
simple file extenstions, you need to write them in this format:

   rule(REGEX => LAMBDA_TRANSFORMER) do
     ACTIONS
   end

The REGEX should match the thing your are trying to build.  The 
LAMBDA_TRANSFORMER is just a lambda expression with a single input that 
transforms the name of the target (i.e. whatever was matched by the 
REGEX) into the target of the task (i.e. the thing the rule is to 
produce).

For example, your regex might be %r{stage1/.*\.png$} to match a file 
that should be in stage 1.  Your lambda could be

  lambda { |fn| fn.sub(/^stage1/, 'source') }

Make appropriate changes for the stage1 to stage2 work.

If you find rules confusing, an alternative is dynamically generate the 
tasks in a list.  For example:

    SRC_FILES = FileList['source/*.png']

    SRC_FILES.each do |fn|
      stage1 = fn.sub(/^source/, 'stage1')
      stage2 = fn.sub(/^source/, 'stage2')
      task stage1 => stage2 do
        do_stage_one_transform(fn, stage1)
      end
      task stage2 => stage1 do
        do_stage_two_transform(stage2, stage1)
      end
    end

In many ways this is easier than rules and just as flexible.

Anyways, here is the example Rakefile using rules:

----------------------------------------------------------------
#!/usr/bin/env ruby

require 'rake/clean'

CLOBBER.include 'stage1', 'stage2'

task :default => %w(stage1 stage2 stage2/a.png)

directory 'stage1'
directory 'stage2'
----------------------------------------------------------------

rule(%r{^stage1/.*\.png$} => lambda { |fn| fn.sub(/^stage1/, 'source') 
}) do |t|
  File.open(t.source) do |ins|
    File.open(t.name, "w") do |outs|
      outs.write ins.read
      outs.puts "Added to stage one"
    end
  end
end

rule(%r{^stage2/.*\.png$} => lambda { |fn| fn.sub(/^stage2/, 'stage1') 
}) do |t|
  File.open(t.source) do |ins|
    File.open(t.name, "w") do |outs|
      outs.write ins.read
      outs.puts "Added to stage two"
    end
  end
end
----------------------------------------------------------------

# Other tasks --------------------------------------------------------

task :init => :clobber do
  File.open("source/a.png", "w") do |outs|
    outs.puts "A PNG FILE"
  end
end

task :see do
  puts "-- Contents of source/a.png -------------------------------"
  puts File.read("source/a.png")
  puts "-- Contents of stage2/a.png -------------------------------"
  puts File.read("stage1/a.png")
  puts "-- Contents of stage2/a.png -------------------------------"
  puts File.read("stage2/a.png")
end
----------------------------------------------------------------

--
-- Jim Weirich

-- 
Posted via http://www.ruby-forum.com/.