Class: FastImage::Gif
- Inherits:
-
Object
- Object
- FastImage::Gif
- Defined in:
- lib/fastimage.rb
Overview
:nodoc:
Instance Method Summary collapse
-
#animated? ⇒ Boolean
Checks if a delay between frames exists and if it does, then the GIFs is animated.
-
#initialize(stream) ⇒ Gif
constructor
A new instance of Gif.
- #width_and_height ⇒ Object
Constructor Details
#initialize(stream) ⇒ Gif
Returns a new instance of Gif.
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# File 'lib/fastimage.rb', line 570 def initialize(stream) @stream = stream end |
Instance Method Details
#animated? ⇒ Boolean
Checks if a delay between frames exists and if it does, then the GIFs is animated
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# File 'lib/fastimage.rb', line 580 def animated? frames = 0 # "GIF" + version (3) + width (2) + height (2) @stream.skip(10) # fields (1) + bg color (1) + pixel ratio (1) fields = @stream.read(3).unpack("CCC")[0] if fields & 0x80 # Global Color Table # 2 * (depth + 1) colors, each occupying 3 bytes (RGB) @stream.skip(3 * 2 ** ((fields & 0x7) + 1)) end loop do block_type = @stream.read(1).unpack("C")[0] if block_type == 0x21 # Graphic Control Extension # extension type (1) + size (1) size = @stream.read(2).unpack("CC")[1] @stream.skip(size) skip_sub_blocks elsif block_type == 0x2C # Image Descriptor frames += 1 return true if frames > 1 # left position (2) + top position (2) + width (2) + height (2) + fields (1) fields = @stream.read(9).unpack("SSSSC")[4] if fields & 0x80 != 0 # Local Color Table # 2 * (depth + 1) colors, each occupying 3 bytes (RGB) @stream.skip(3 * 2 ** ((fields & 0x7) + 1)) end @stream.skip(1) # LZW min code size (1) skip_sub_blocks else break # unrecognized block end end false end |
#width_and_height ⇒ Object
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# File 'lib/fastimage.rb', line 574 def width_and_height @stream.read(11)[6..10].unpack('SS') end |