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)

Returns a new instance of Field



500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
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
# File 'lib/exifr/tiff.rb', line 500

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



498
499
500
# File 'lib/exifr/tiff.rb', line 498

def offset
  @offset
end

- (Object) tag (readonly)

Returns the value of attribute tag



498
499
500
# File 'lib/exifr/tiff.rb', line 498

def tag
  @tag
end

- (Object) value (readonly)

Returns the value of attribute value



498
499
500
# File 'lib/exifr/tiff.rb', line 498

def value
  @value
end