ImageX.rb

# encoding: ascii-8bit
require 'zlib'

class Image

  RGB = 2
  RGBA = 6

  #-----------------------------------------------
  # Header BMP
  #-----------------------------------------------

  def self.header_bmp(width, height)
    # BMP header
    [19778, (((24 * width + 31) >> 5) * height << 2) + 54, 54,
    # DIB header
    40, width, height, 1, 24].pack('slx4l4s2x24')
  end

  #-----------------------------------------------
  # Load BMP
  #-----------------------------------------------

  def self.load_bmp(filename)
    width, height, data = File.binread(filename).unpack('x18l2x28a*')
    image = new(width, height)
    padding = width & 3
    w3 = width << 3
    index = -3
    index_image = (width * height.pred).pred << 2
    height.times {
      width.times {image.write(index_image += 4, 0, data.byteslice(index += 3, 3) << 255, 4)}
      index_image -= w3
      index += padding
    }
    image
  end

  #-----------------------------------------------
  # Save BMP
  #-----------------------------------------------

  def save_bmp(filename)
    File.open(filename,'wb') {|file|
      file << Image.header_bmp(width, height)
      size = width * height << 2
      data = ' ' * size
      read(0, 0, data, size)
      padding = ' ' * (width & 3)
      index = size - (width.succ << 2)
      w = width << 3
      height.times {
        width.times {file << data.byteslice(index += 4, 3)}
        file << padding
        index -= w
      }
    }
  end

  #-----------------------------------------------
  # Load PNG
  #-----------------------------------------------

  def self.load_png(filename)
    image = nil
    File.open(filename,'rb') {|file|
      width = height = color_type = 0
      # Signature
      file.pos = 8
      loop {
        size, type = file.read(8).unpack('NA4')
        case type
        when 'IHDR'
          width, height, color_type = file.read(13).unpack('N2xC')
        when 'IDAT' # Support only single IDAT chunk
          image = new(width, height)
          data = Zlib::Inflate.inflate(file.read(size)).reverse!
          index_image = -4
          index = data.size
          if color_type == RGB
            height.times {
              index -= 1
              width.times {image.write(index_image += 4, 0, data.byteslice(index -= 3, 3) << 255, 4)}
            }
          else
            height.times {
              index -= 1
              width.times {image.write(index_image += 4, 0, data.byteslice(index -= 3, 3) << data.getbyte(index -= 1), 4)}
            }
          end
        when 'IEND'
          break
        else file.pos += size
        end
        # CRC
        file.pos += 4
      }
    }
    image
  end

  #-----------------------------------------------
  # Save PNG
  #-----------------------------------------------

  def save_png(filename, color_type = RGB)
    size = width * height << 2
    data = ' ' * size
    read(0, 0, data, size)
    data.reverse!
    img_data = ''
    index = size.succ
    if color_type == RGB
      height.times {
        img_data << 0
        width.times {img_data << data.byteslice(index -= 4, 3)}
      }
    else
      height.times {
        img_data << 0
        width.times {img_data << data.byteslice(index -= 4, 3) << data.getbyte(index.pred)}
      }
    end
    Image.save_png_data(filename, img_data, width, height, color_type)
  end

  #-----------------------------------------------
  # Save PNG data
  #-----------------------------------------------

  def self.save_png_data(filename, data, width, height, color_type)
    File.binwrite(filename, "\x89PNG\r\n\x1a\n" <<
      chunk('IHDR', [width, height, 8, color_type].pack('N2C2x3')) <<
      chunk('IDAT', Zlib::Deflate.deflate(data, 9)) <<
      "\0\0\0\0IEND\xAEB`\x82")
  end

  #-----------------------------------------------
  # Chunk
  #-----------------------------------------------

  def self.chunk(type, data)
    [data.size, type << data, Zlib.crc32(type)].pack('NA*N')
  end

  #-----------------------------------------------
  # Save SVG
  #-----------------------------------------------

  def save_svg(filename, r = nil, g = nil, b = nil)
    size = width * height << 2
    data = ' ' * size
    read(0, 0, data, size)
    File.open(filename,'w') {|file|
      file << "<svg xmlns=\"http://www.w3.org/2000/svg\" width=\"#{width}\" height=\"#{height}\""
      if r and g and b
        file.printf(' style="background:#%02x%02x%02x"', r, g, b)
        background = [b, g, r].pack('C3')
      end
      file << '>'
      paths = Hash.new {|h,k| h[k] = ''}
      c = data.byteslice(index = 0, 3)
      height.times {|y|
        i = 0
        color = c
        width.times {|x|
          if color != c
            paths[color] << sprintf('M%d %dh%dv1H%d', i, y, x - i, i) if color != background
            i = x
            color = c
          end
          c = data.byteslice(index += 4, 3)
        }
        paths[color] << sprintf('M%d %dh%dv1H%d', i, y, width - i, i) if color != background
      }
      paths.each {|color,path| file.printf('<path d="%s" fill="#%02x%02x%02x"/>', path, *color.bytes.reverse!)}
      file << '</svg>'
    }
  end
end