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module FastImageParsing
class Webp < ImageBase # :nodoc:
def dimensions
vp8 = @stream.read(16)[12..15]
_len = @stream.read(4).unpack("V")
case vp8
when "VP8 "
parse_size_vp8
when "VP8L"
parse_size_vp8l
when "VP8X"
parse_size_vp8x
else
nil
end
end
def animated?
vp8 = @stream.read(16)[12..15]
_len = @stream.read(4).unpack("V")
case vp8
when "VP8 "
false
when "VP8L"
false
when "VP8X"
flags = @stream.read(4).unpack("C")[0]
flags & 2 > 0
else
nil
end
end
private
def parse_size_vp8
w, h = @stream.read(10).unpack("@6vv")
[w & 0x3fff, h & 0x3fff]
end
def parse_size_vp8l
@stream.skip(1) # 0x2f
b1, b2, b3, b4 = @stream.read(4).bytes.to_a
[1 + (((b2 & 0x3f) << 8) | b1), 1 + (((b4 & 0xF) << 10) | (b3 << 2) | ((b2 & 0xC0) >> 6))]
end
def parse_size_vp8x
flags = @stream.read(4).unpack("C")[0]
b1, b2, b3, b4, b5, b6 = @stream.read(6).unpack("CCCCCC")
width, height = 1 + b1 + (b2 << 8) + (b3 << 16), 1 + b4 + (b5 << 8) + (b6 << 16)
if flags & 8 > 0 # exif
# parse exif for orientation
# TODO: find or create test images for this
end
[width, height]
end
end
end
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