Initial commit of file.

bmpencode.rb

+#!/usr/bin/env ruby
+require 'optparse'
+
+# Option parsing
+inputfile  = ''
+outputfile = ''
+width      = 0
+height     = 0
+padding    = 0
+decode     = false
+  
+ARGV.options do |opts|
+  opts.separator 'When no filenames are provided STDIO is used'
+  opts.separator 'When no width is provided a the square root of the input size is used.'
+  opts.on('-i', '--input=filename',  'Read input from file')             { |val| inputfile  = val }
+  opts.on('-o', '--output=filename', 'Write output to file')             { |val| outputfile = val }
+  opts.on('-w', '--width=value',     'Make image "value" pixels wide')   { |val| width = val.to_i }
+  opts.on('-p', '--padding',         'Pad pixel rows with 0-bytes to ensure all data is in pixel values') { padding = 1 }
+  opts.on('-d', '--decode',          'Decode bmp back to original file') { decode = true }
+  opts.parse!
+end
+
+# Start reading input
+data   = ''
+output = ''
+if(inputfile == '')
+  data = ARGF.read
+else
+  data = IO.binread(inputfile)
+end
+
+if(decode)
+  # Decoding
+
+  # Read headers we care about
+  data    = data.bytes
+  padsize = data[6..7].pack('C*').unpack('S_')[0]
+  padding = data[8..9].pack('C*').unpack('S_')[0]
+  width   = data[18..21].pack('C*').unpack('I')[0]
+
+  # Calculate end of data
+  dend   = data.size - padsize - 1
+
+  # Calculate row padding
+  rowpadsize = (width * 3) % 4
+  if(rowpadsize > 0)
+    rowpadsize = 4 - rowpadsize
+  end
+
+  # Decode
+  if(padding == 1 && rowpadsize != 0)
+
+    pc = 0
+    data[54..-1].pack('C*').each_byte { |b|
+      pc +=1
+      if(pc > width * 3)
+        if(pc == (width * 3) + rowpadsize)
+          pc = 0
+        end
+        
+        next
+      else
+        output.concat([b].pack('C*'))
+      end
+
+    }
+    dend   = -1 - padsize
+    output = output.bytes[0..dend].pack('C*')
+  else
+    output = data[54..dend].pack('C*')
+  end
+else
+  # Encoding
+
+  # Add padding if needed
+  padsize = data.bytesize % 4
+  if(padsize > 0)
+    padsize = 4 - padsize
+  end
+  data = data.concat([0x00].pack('C*') * padsize)
+
+  # Calculate image dimensions
+  if(width == 0)
+    width  = Math.sqrt(data.bytesize / 3).ceil()
+    height = width
+  else
+    height = ((data.bytesize / 3) / width.to_f).ceil()
+  end
+
+  # Calculate extra bytes required for row padding
+  rowpadsize = (width * 3) % 4
+  if(rowpadsize > 0)
+    rowpadsize = 4 - rowpadsize
+  end
+  totalrowpad = 0
+  if(padding == 1)
+    totalrowpad = rowpadsize * height
+  end
+
+  # Construct BMP header
+  bfType      = [0x42, 0x4D]                  # BMP specification type
+  bfSize      = [54 + data.bytesize + totalrowpad] # File size
+  bfReserved1 = [padsize]                     # Reserved, always 0 [abused to store number of padding bytes added for alignment]
+  bfReserved2 = [padding]                     # Reserved, always 0 [abused to store if extra row padding was used]
+  bfOffBits   = [0x36, 0x00, 0x00, 0x00]      # Offset to start of image data
+
+  # Construct image header
+  biSize          = [0x28, 0x00, 0x00, 0x00] # Image header size [always 40 bytes here]
+  biWidth         = [width]                  # Image width in px
+  biHeight        = [height]                 # Image height in px
+  biPlanes        = [0x01, 0x00]             # BMP planes [Always 1]
+  biBitCount      = [0x18, 0x00]             # Bits per pixel [Always 24 here]
+  biCompression   = [0x00, 0x00, 0x00, 0x00] # Compression [Always no compression here]
+  biSizeImage     = [0x00, 0x00, 0x00, 0x00] # Image size [May be 0 because no compression is used]
+  biXPelsPerMeter = [0x13, 0x0B, 0x00, 0x00] # Preferred resolution in pixels per meter
+  biYPelsPerMeter = [0x13, 0x0B, 0x00, 0x00] # Preferred resolution in pixels per meter
+  biClrUsed       = [0x00, 0x00, 0x00, 0x00] # Number of Color Map entities used [unused here]
+  biClrImportant  = [0x00, 0x00, 0x00, 0x00] # Number of signifcant colors [unused here]
+
+  # Print headers
+  output.concat(bfType.pack('C*'))
+  output.concat(bfSize.pack('I'))
+  output.concat(bfReserved1.pack('S_'))
+  output.concat(bfReserved2.pack('S_'))
+  output.concat(bfOffBits.pack('C*'))
+
+  output.concat(biSize.pack('C*'))
+  output.concat(biWidth.pack('I'))
+  output.concat(biHeight.pack('I'))
+  output.concat(biPlanes.pack('C*'))
+  output.concat(biBitCount.pack('C*'))
+  output.concat(biCompression.pack('C*'))
+  output.concat(biSizeImage.pack('I'))
+  output.concat(biXPelsPerMeter.pack('C*'))
+  output.concat(biYPelsPerMeter.pack('C*'))
+  output.concat(biClrUsed.pack('C*'))
+  output.concat(biClrImportant.pack('C*'))
+
+  # Print content
+  if(padding == 1)
+    pc = 0
+    data.each_byte { |b|
+      pc += 1
+      output.concat([b].pack('C*'))
+
+      if(pc == width * 3)
+        output.concat([0x00].pack('C*') * rowpadsize)
+        pc = 0
+      end
+    }
+  else
+    output.concat(data)
+  end
+end
+
+# Write out results
+if(outputfile == '')
+  print output
+else
+  IO.binwrite(outputfile, output)
+end
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