Class: EXIFR::TIFF::Field

Inherits:
Object
  • Object
show all
Defined in:
lib/exifr/tiff.rb

Overview

:nodoc:

Instance Attribute Summary (collapse)

Instance Method Summary (collapse)

Constructor Details

- (Field) initialize(data, pos)



526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
# File 'lib/exifr/tiff.rb', line 526

def initialize(data, pos)
  @tag, count, @offset = data.readshort(pos), data.readlong(pos + 4), data.readlong(pos + 8)
  @type = data.readshort(pos + 2)

  case @type
  when 1 # byte
    len, pack = count, proc { |d| d }
  when 6 # signed byte
    len, pack = count, proc { |d| sign_byte(d) }
  when 2 # ascii
    len, pack = count, proc { |d| d.unpack("A*") }
  when 3 # short
    len, pack = count * 2, proc { |d| d.unpack(data.short + '*') }
  when 8 # signed short
    len, pack = count * 2, proc { |d| d.unpack(data.short + '*').map{|n| sign_short(n)} }
  when 4 # long
    len, pack = count * 4, proc { |d| d.unpack(data.long + '*') }
  when 9 # signed long
    len, pack = count * 4, proc { |d| d.unpack(data.long + '*').map{|n| sign_long(n)} }
  when 7 # undefined
    # UserComment
    if @tag == 0x9286
      len, pack = count, proc { |d| d.strip }
      len -= 8 # reduce to account for first 8 bytes
      start = len > 4 ? @offset + 8 : (pos + 8) # UserComment first 8-bytes is char code
      @value = [pack[data[start..(start + len - 1)]]].flatten
    end
  when 5 # unsigned rational
    len, pack = count * 8, proc do |d|
      rationals = []
      d.unpack(data.long + '*').each_slice(2) do |f|
        rationals << rational(*f)
      end
      rationals
    end
  when 10 # signed rational
    len, pack = count * 8, proc do |d|
      rationals = []
      d.unpack(data.long + '*').map{|n| sign_long(n)}.each_slice(2) do |f|
        rationals << rational(*f)
      end
      rationals
    end
  end

  if len && pack && @type != 7
    start = len > 4 ? @offset : (pos + 8)
    d = data[start..(start + len - 1)]
    @value = d && [pack[d]].flatten
  end
end

Instance Attribute Details

- (Object) offset (readonly)

Returns the value of attribute offset



524
525
526
# File 'lib/exifr/tiff.rb', line 524

def offset
  @offset
end

- (Object) tag (readonly)

Returns the value of attribute tag



524
525
526
# File 'lib/exifr/tiff.rb', line 524

def tag
  @tag
end

- (Object) value (readonly)

Returns the value of attribute value



524
525
526
# File 'lib/exifr/tiff.rb', line 524

def value
  @value
end