Class: ZPNG::ScanLine

Inherits:
Object
  • Object
show all
Defined in:
lib/zpng/scan_line.rb,
lib/zpng/scan_line/mixins.rb

Defined Under Namespace

Modules: Mixins

Constant Summary collapse

FILTER_NONE = 
0
FILTER_SUB = 
1
FILTER_UP = 
2
FILTER_AVERAGE = 
3
FILTER_PAETH = 
4

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(image, idx, params = {}) ⇒ ScanLine

Returns a new instance of ScanLine.



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# File 'lib/zpng/scan_line.rb', line 13

def initialize image, idx, params={}
  @image,@idx = image,idx
  @bpp = image.hdr.bpp
  raise "[!] zero bpp" if @bpp == 0

  # Bytes Per Pixel, if bpp = 8, 16, 24, 32
  # NULL otherwise
  @BPP = (@bpp%8 == 0) && (@bpp>>3)

  if @image.new?
    @size = params[:size]
    @decoded_bytes = params[:decoded_bytes] || "\x00" * (size-1)
    @filter = FILTER_NONE
    @offset = params[:offset] || idx*size
  else
    @offset =
      if image.interlaced?
        image.adam7.scanline_offset(idx)
      else
        idx*size
      end
    if @filter = image.imagedata[@offset]
      @filter = @filter.ord
    else
      STDERR.puts "[!] #{self.class}: ##@idx: no data at pos 0, scanline dropped".red
    end
  end
end

Instance Attribute Details

#bpp ⇒ Object

Returns the value of attribute bpp.



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# File 'lib/zpng/scan_line.rb', line 10

def bpp
  @bpp
end

#decoded_bytes ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 237

def decoded_bytes
  #raise if caller.size > 50
  @decoded_bytes ||=
    begin
      imagedata = @image.imagedata

      # number of bytes per complete pixel, rounding up to one
      bpp1 = (@bpp/8.0).ceil

      case @filter

      when FILTER_NONE    # 0
        s = imagedata[@offset+1, size-1]

      when FILTER_SUB     # 1
        s = "\x00" * (size-1)
        s[0,bpp1] = imagedata[@offset+1,bpp1]
        bpp1.upto(size-2) do |i|
          s.setbyte(i, imagedata.getbyte(@offset+i+1) + s.getbyte(i-bpp1))
        end

      when FILTER_UP      # 2
        s = "\x00" * (size-1)
        0.upto(size-2) do |i|
          s.setbyte(i, imagedata.getbyte(@offset+i+1) + prev_scanline_byte(i))
        end

      when FILTER_AVERAGE # 3
        s = "\x00" * (size-1)
        0.upto(bpp1-1) do |i|
          s.setbyte(i, imagedata.getbyte(@offset+i+1) + prev_scanline_byte(i)/2)
        end
        bpp1.upto(size-2) do |i|
          s.setbyte(i,
            imagedata.getbyte(@offset+i+1) + (s.getbyte(i-bpp1) + prev_scanline_byte(i))/2
          )
        end

      when FILTER_PAETH   # 4
        s = "\x00" * (size-1)
        0.upto(bpp1-1) do |i|
          s.setbyte(i, imagedata.getbyte(@offset+i+1) + prev_scanline_byte(i))
        end
        bpp1.upto(size-2) do |i|
          s.setbyte(i,
            imagedata.getbyte(@offset+i+1) +
            paeth_predictor(s.getbyte(i-bpp1), prev_scanline_byte(i), prev_scanline_byte(i-bpp1))
          )
        end

      else raise "invalid ScanLine filter #{@filter}"
      end

      s
    end
end

#filter ⇒ Object

Returns the value of attribute filter.



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# File 'lib/zpng/scan_line.rb', line 10

def filter
  @filter
end

#idx ⇒ Object

Returns the value of attribute idx.



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# File 'lib/zpng/scan_line.rb', line 10

def idx
  @idx
end

#image ⇒ Object

Returns the value of attribute image.



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# File 'lib/zpng/scan_line.rb', line 10

def image
  @image
end

#offset ⇒ Object

Returns the value of attribute offset.



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# File 'lib/zpng/scan_line.rb', line 10

def offset
  @offset
end

Instance Method Details

#[](x) ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 143

def [] x
  raw =
    if @BPP
      # 8, 16, 24, 32, 48 bits per pixel
      decoded_bytes[x*@BPP, @BPP]
    else
      # 1, 2 or 4 bits per pixel
      decoded_bytes[x*@bpp/8]
    end

  case image.hdr.color
  when COLOR_INDEXED                # ALLOWED_DEPTHS: 1, 2, 4, 8
    mask  = 2**@bpp-1
    shift = 8-(x%(8/@bpp)+1)*@bpp
    raise "invalid shift #{shift}" if shift < 0 || shift > 7
    idx = (raw.ord >> shift) & mask
    if image.trns
      # transparency from tRNS chunk
      # For color type 3 (indexed color), the tRNS chunk contains a series of one-byte alpha values,
      # corresponding to entries in the PLTE chunk:
      #
      #   Alpha for palette index 0:  1 byte
      #   Alpha for palette index 1:  1 byte
      #   ...
      #
      color = image.palette[idx].dup
      if color.alpha = image.trns.data[idx]
        # if it's not NULL - convert it from char to int,
        # otherwise it means fully opaque color, as well as NULL alpha in ZPNG::Color
        color.alpha = color.alpha.ord
      end
      return color
    else
      # no transparency
      return image.palette[idx]
    end

  when COLOR_GRAYSCALE              # ALLOWED_DEPTHS: 1, 2, 4, 8, 16
    c = if @bpp == 16
          raw.unpack('n')[0]
        else
          mask  = 2**@bpp-1
          shift = 8-(x%(8/@bpp)+1)*@bpp
          raise "invalid shift #{shift}" if shift < 0 || shift > 7
          (raw.ord >> shift) & mask
        end

    color = Color.from_grayscale(c, :depth => @bpp) # only in this color mode depth == bpp
    color.alpha = image._alpha_color(color)
    return color

  when COLOR_RGB                    # ALLOWED_DEPTHS: 8, 16
    color =
      case @bpp
      when 24                     # RGB  8 bits per sample = 24bpp
        if image.trns
          extend Mixins::RGB24_TRNS
        else
          extend Mixins::RGB24
        end
        return self[x]
      when 48                     # RGB 16 bits per sample = 48bpp
        Color.new(*raw.unpack('n3'), :depth => 16)
      else raise "COLOR_RGB unexpected bpp #@bpp"
      end

    color.alpha = image._alpha_color(color)
    return color

  when COLOR_GRAY_ALPHA             # ALLOWED_DEPTHS: 8, 16
    case @bpp
    when 16                         #  8-bit grayscale +  8-bit alpha
      return Color.from_grayscale(*raw.unpack('C2'))
    when 32                         # 16-bit grayscale + 16-bit alpha
      return Color.from_grayscale(*raw.unpack('n2'), :depth => 16)
    else raise "COLOR_GRAY_ALPHA unexpected bpp #@bpp"
    end

  when COLOR_RGBA                   # ALLOWED_DEPTHS: 8, 16
    case @bpp
    when 32                         # RGBA  8-bit/sample
      extend Mixins::RGBA32
      return self[x]
    when 64                         # RGBA 16-bit/sample
      return Color.new(*raw.unpack('n4'), :depth => 16 )
    else raise "COLOR_RGBA unexpected bpp #@bpp"
    end

  else
    raise "unexpected color mode #{image.hdr.color}"

  end # case img.hdr.color
end

#[]=(x, color) ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 84

def []= x, color
  case image.hdr.color
  when COLOR_INDEXED                # ALLOWED_DEPTHS: 1, 2, 4, 8
    color_idx = image.palette.find_or_add(color)
    raise "no color #{color.inspect} in palette" unless color_idx

    mask  = 2**@bpp-1
    shift = 8-(x%(8/@bpp)+1)*@bpp
    raise "invalid shift #{shift}" if shift < 0 || shift > 7

    pos = x*@bpp/8
    b = decoded_bytes.getbyte(pos)
    b = (b & (0xff-(mask<<shift))) | ((color_idx & mask) << shift)
    decoded_bytes.setbyte(pos, b)
    # TODO: transparency in TRNS

  when COLOR_GRAYSCALE              # ALLOWED_DEPTHS: 1, 2, 4, 8, 16
    raw = color.to_depth(@bpp).to_grayscale
    pos = x*@bpp/8
    if @bpp == 16
      decoded_bytes[pos,2] = [raw].pack('n')
    else
      mask  = 2**@bpp-1
      shift = 8-(x%(8/@bpp)+1)*@bpp
      raise "invalid shift #{shift}" if shift < 0 || shift > 7
      b = decoded_bytes[pos].ord
      b = (b & (0xff-(mask<<shift))) | ((raw & mask) << shift)
      decoded_bytes[pos] = b.chr
    end
    # TODO: transparency in TRNS

  when COLOR_RGB                    # ALLOWED_DEPTHS: 8, 16
    case @bpp
    when 24; decoded_bytes[x*3,3] = color.to_depth(8).to_a.pack('C3')
    when 48; decoded_bytes[x*6,6] = color.to_depth(16).to_a.pack('n3')
    else raise "unexpected bpp #@bpp"
    end
    # TODO: transparency in TRNS

  when COLOR_GRAY_ALPHA             # ALLOWED_DEPTHS: 8, 16
    case @bpp
    when 16; decoded_bytes[x*2,2] = color.to_depth(8).to_gray_alpha.pack('C2')
    when 32; decoded_bytes[x*4,4] = color.to_depth(16).to_gray_alpha.pack('n2')
    else raise "unexpected bpp #@bpp"
    end

  when COLOR_RGBA                   # ALLOWED_DEPTHS: 8, 16
    case @bpp
    when 32; decoded_bytes[x*4,4] = color.to_depth(8).to_a.pack('C4')
    when 64; decoded_bytes[x*8,8] = color.to_depth(16).to_a.pack('n4')
    else raise "unexpected bpp #@bpp"
    end

  else
    raise "unexpected color mode #{image.hdr.color}"

  end # case image.hdr.color
end

#bad? ⇒ Boolean

ScanLine is BAD if it has no filter

Returns:

  • (Boolean) 


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# File 'lib/zpng/scan_line.rb', line 43

def bad?
  !@filter
end

#crop!(x, w) ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 327

def crop! x, w
  @size = nil # unmemoize self size b/c it's changed after crop
  if @BPP
    # great, crop is byte-aligned! :)
    decoded_bytes[0,x*@BPP]   = ''
    decoded_bytes[w*@BPP..-1] = ''
  else
    # oh, no we have to shift bits in a whole line :(
    case @bpp
    when 1,2,4
      cut_bits_head = @bpp*x
      if cut_bits_head > 8
        # cut whole head bytes
        decoded_bytes[0,cut_bits_head/8] = ''
      end
      cut_bits_head %= 8
      if cut_bits_head > 0
        # bit-shift all remaining bytes
        (w*@bpp/8.0).ceil.times do |i|
          decoded_bytes[i] = ((
            (decoded_bytes[i].ord<<cut_bits_head) |
            (decoded_bytes[i+1].ord>>(8-cut_bits_head))
          ) & 0xff).chr
        end
      end

      new_width_bits = w*@bpp
      diff = decoded_bytes.size*8 - new_width_bits
      raise if diff < 0
      if diff > 8
        # cut whole tail bytes
        decoded_bytes[(new_width_bits/8.0).ceil..-1] = ''
      end
      diff %= 8
      if diff > 0
        # zero tail bits of last byte
        decoded_bytes[-1] = (decoded_bytes[-1].ord & (0xff-(2**diff)+1)).chr
      end

    else
      raise "unexpected bpp=#@bpp"
    end
  end
end

#decode! ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 294

def decode!
  decoded_bytes
  true
end

#each_pixel ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 377

def each_pixel
  width.times do |i|
    yield self[i], i
  end
end

#export ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 372

def export
  # we export in FILTER_NONE mode
  FILTER_NONE.chr + decoded_bytes
end

#inspect ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 68

def inspect
  if image.interlaced?
    "#<ZPNG::ScanLine idx=%-2d offset=%-3d width=%-2d size=%-2d bpp=%d filter=%d>" %
      [idx, offset, width, size, bpp, filter]
  else
    "#<ZPNG::ScanLine idx=%-2d offset=%-3d size=%-2d bpp=%d filter=%d>" %
      [idx, offset, size, bpp, filter]
  end
end

#pixels ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 383

def pixels
  Pixels.new(self)
end

#raw_data ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 299

def raw_data
  @offset ? @image.imagedata[@offset, size] : ''
end

#size ⇒ Object

total scanline size in bytes, INCLUDING leading ‘filter’ byte



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# File 'lib/zpng/scan_line.rb', line 48

def size
  @size ||=
    begin
      if @BPP
        width*@BPP+1
      else
        (width*@bpp/8.0+1).ceil
      end
    end
end

#to_ascii(*args) ⇒ Object 



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# File 'lib/zpng/scan_line.rb', line 78

def to_ascii *args
  @image.width.times.map do |i|
    self[i].to_ascii(*args)
  end.join
end

#width ⇒ Object

scanline width in pixels



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# File 'lib/zpng/scan_line.rb', line 60

def width
  if image.interlaced?
    image.adam7.scanline_width(idx)
  else
    image.width
  end
end