Convert SEGA Dreamcast PVR images to PNG ones (of an entire directory, recursively), using Pvr2Png.exe and and the Ruby gem chunky_png. [It has specifically been used to convert Shenmue's PVR files to PNGs.]

pvr2png.rb

require "chunky_png"

class Dir
  def self.each_valid_file(path = "**/*")
    glob(path) { |f|
      File.directory?(f) or f == File.basename(__FILE__) or yield f
    }
  end
  def self.exist_or_make(name)
    File.exist?(name) or mkdir(name)
  end
end

class File
  def self.pvrDissect(f)
    string = IO.binread(f); stringSize = string.size; curOffset = 0
    while curOffset < stringSize
      curOffset = string.index("PVRT", curOffset) or break; curOffset += 4
      pvrSize = string[ curOffset...(curOffset + 4) ].unpack("H*")[0].split(/(\d{2})/).reject(&:empty?).reverse.join.hex
      pvrSize > stringSize and break
      yield string[ (curOffset - 16)...curOffset + 4 ] + string[curOffset + 4, pvrSize]
    end
  end
end

inputPath = Dir.pwd
outputRootDir = "EXTRACTS"; outputRootPath = "#{inputPath}/#{outputRootDir}"
outputPathPNGs = "#{outputRootPath}/PNGs"
outputPathPVRs = "#{outputRootPath}/PVRs"

# "If the output directories don't exist, then they're created [in the right order, from the outside to the inside]"
[outputRootPath, outputPathPNGs, outputPathPVRs].each { |path| Dir.exist_or_make(path) }

# "Start accessing the whole of the sub-tree."
Dir.glob("#{inputPath}/**/*") { |element| # "For each element found:"
  element[0, outputRootPath.size] == outputRootPath and next # "if it's found in the root directory, it's ignored, else"
  
  elementFilename = File.basename(element)
  elementPath = File.dirname(element)

  outputPathPNG = elementPath.sub(inputPath, outputPathPNGs); cmdOutputPathPNG = outputPathPNG.gsub("/", "\\")
  outputPathPVR = elementPath.sub(inputPath, outputPathPVRs); cmdOutputPathPVR = outputPathPVR.gsub("/", "\\")

  if File.directory?(element) # "if it's a directory:"
  # "if they don't exist already, create in each of the output sub-directories a directory named as the element"
    Dir.exist_or_make("#{outputPathPNG}/#{elementFilename}")
    Dir.exist_or_make("#{outputPathPVR}/#{elementFilename}")
  else # "if it's not a directory (and thus it's a file):"
    element == File.basename(__FILE__) and next # "if it's the file __FILE__, it's ignored, else"
    id = 0

    File.pvrDissect(element) { |data| # "dissect it and"
    # "save the result in the matching (based on which directory it's found) directory of PVRs"
      suffixPNG = "#{elementFilename}_\##{id}.PNG"; suffixPVR = "#{elementFilename}_\##{id}.PVR"
      id += 1; IO.binwrite("#{outputPathPVR}/#{suffixPVR}", data)            
      %x{Pvr2Png.exe #{ "#{cmdOutputPathPVR}\\#{suffixPVR}" } #{ "#{cmdOutputPathPNG}\\#{suffixPNG}" } }
      begin
        outputPNG = "#{outputPathPNG}/#{suffixPNG}"
        ChunkyPNG::Image.from_file(outputPNG).flip.save(outputPNG)
      rescue
        next
      end
    }
  end
}