Sha256: bbd0c4daaedbd12e5449171ac84298f539794740294ce5300c1f22f18e61fecf
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Contents
# encoding: ASCII-8BIT
# jpg.rb : Extracts the data from a JPG that is needed for embedding
#
# Copyright April 2008, James Healy. All Rights Reserved.
#
# This is free software. Please see the LICENSE and COPYING files for details.
require 'stringio'
module Prawn
module Images
# A convenience class that wraps the logic for extracting the parts
# of a JPG image that we need to embed them in a PDF
#
class JPG
attr_reader :width, :height, :bits, :channels
attr_accessor :scaled_width, :scaled_height
JPEG_SOF_BLOCKS = %W(\xc0 \xc1 \xc2 \xc3 \xc5 \xc6 \xc7 \xc9 \xca \xcb \xcd \xce \xcf)
JPEG_APP_BLOCKS = %W(\xe0 \xe1 \xe2 \xe3 \xe4 \xe5 \xe6 \xe7 \xe8 \xe9 \xea \xeb \xec \xed \xee \xef)
# Process a new JPG image
#
# <tt>:data</tt>:: A string containing a full PNG file
#
def initialize(data)
data = StringIO.new(data.dup)
c_marker = "\xff" # Section marker.
data.read(2) # Skip the first two bytes of JPEG identifier.
loop do
marker, code, length = data.read(4).unpack('aan')
raise "JPEG marker not found!" if marker != c_marker
if JPEG_SOF_BLOCKS.include?(code)
@bits, @height, @width, @channels = data.read(6).unpack("CnnC")
break
end
buffer = data.read(length - 2)
end
end
end
end
end
Version data entries
6 entries across 6 versions & 2 rubygems