Class: ZPNG::Image

Inherits:
Object
  • Object
show all
Defined in:
lib/zpng/image.rb

Constant Summary collapse

PNG_HDR = 
"\x89PNG\x0d\x0a\x1a\x0a"

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(x = nil) ⇒ Image

Returns a new instance of Image.



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# File 'lib/zpng/image.rb', line 8

def initialize x = nil
  if x
    if x[PNG_HDR]
      # raw image data
      @data = x
    else
      # filename
      @data = File.binread(x)
    end
  end

  d = data[0,PNG_HDR.size]
  if d != PNG_HDR
    puts "[!] first #{PNG_HDR.size} bytes must be #{PNG_HDR.inspect}, but got #{d.inspect}".red
  end

  io = StringIO.new(data)
  io.seek PNG_HDR.size
  @chunks = []
  while !io.eof?
    chunk = Chunk.from_stream(io)
    @chunks << chunk
    case chunk
    when Chunk::IHDR
      @header = chunk
    when Chunk::PLTE
      @palette = chunk
    when Chunk::IEND
      break
    end
  end
  unless io.eof?
    offset    = io.tell
    extradata = io.read
    puts "[?] #{extradata.size} bytes of extra data after image end (IEND), offset = 0x#{offset.to_s(16)}".red
  end
end

Instance Attribute Details

#chunks ⇒ Object

Returns the value of attribute chunks.



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# File 'lib/zpng/image.rb', line 3

def chunks
  @chunks
end

#data ⇒ Object

Returns the value of attribute data.



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# File 'lib/zpng/image.rb', line 3

def data
  @data
end

#header ⇒ Object Also known as: hdr

Returns the value of attribute header.



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# File 'lib/zpng/image.rb', line 3

def header
  @header
end

#imagedata ⇒ Object

Returns the value of attribute imagedata.



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# File 'lib/zpng/image.rb', line 3

def imagedata
  @imagedata
end

#palette ⇒ Object

Returns the value of attribute palette.



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# File 'lib/zpng/image.rb', line 3

def palette
  @palette
end

#scanlines ⇒ Object

Returns the value of attribute scanlines.



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# File 'lib/zpng/image.rb', line 3

def scanlines
  @scanlines
end

Instance Method Details

#[](x, y) ⇒ Object 



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# File 'lib/zpng/image.rb', line 69

def [] x, y
  scanlines[y][x]
end

#[]=(x, y, newpixel) ⇒ Object 



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# File 'lib/zpng/image.rb', line 73

def []= x, y, newpixel
  # we must decode all scanlines before doing any modifications
  # or scanlines decoded AFTER modification of UPPER ones will be decoded wrong
  _decode_all_scanlines unless @_all_scanlines_decoded
  scanlines[y][x] = newpixel
end

#_decode_all_scanlines ⇒ Object 



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# File 'lib/zpng/image.rb', line 80

def _decode_all_scanlines
  scanlines.each(&:decode!)
  @_all_scanlines_decoded = true
end

#dump ⇒ Object 



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# File 'lib/zpng/image.rb', line 46

def dump
  @chunks.each do |chunk|
    puts "[.] #{chunk.inspect} #{chunk.crc_ok? ? 'CRC OK'.green : 'CRC ERROR'.red}"
  end
end

#each_block(bw, bh, &block) ⇒ Object 



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# File 'lib/zpng/image.rb', line 108

def each_block bw,bh, &block
  0.upto(height/bh-1) do |by|
    0.upto(width/bw-1) do |bx|
      b = extract_block(bx*bw, by*bh, bw, bh)
      yield b
    end
  end
end

#export ⇒ Object 



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# File 'lib/zpng/image.rb', line 117

def export
  imagedata # fill @imagedata, if not already filled

  # delete redundant IDAT chunks
  first_idat = @chunks.find{ |c| c.type == 'IDAT' }
  @chunks.delete_if{ |c| c.type == 'IDAT' && c != first_idat }

  # fill first_idat @data with compressed imagedata
  first_idat.data = Zlib::Deflate.deflate(scanlines.map(&:export).join, 9)

  PNG_HDR + @chunks.map(&:export).join
end

#extract_block(x, y = nil, w = nil, h = nil) ⇒ Object 



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# File 'lib/zpng/image.rb', line 100

def extract_block x,y=nil,w=nil,h=nil
  if x.is_a?(Hash)
    Block.new(self,x[:x], x[:y], x[:width], x[:height])
  else
    Block.new(self,x,y,w,h)
  end
end

#height ⇒ Object 



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# File 'lib/zpng/image.rb', line 56

def height
  @header && @header.height
end

#to_s(h = {}) ⇒ Object 



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# File 'lib/zpng/image.rb', line 96

def to_s h={}
  scanlines.map{ |l| l.to_s(h) }.join("\n")
end

#width ⇒ Object 



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# File 'lib/zpng/image.rb', line 52

def width
  @header && @header.width
end