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77 lines
1.4 KiB
77 lines
1.4 KiB
class Base64ImageConverter
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BASE64_HEAD = 'data:image/jpeg;base64,'.freeze
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Error = Class.new(StandardError)
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OutLimit = Class.new(Error)
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InvalidData = Class.new(Error)
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InvalidFormat = Class.new(Error)
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attr_reader :opts
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def initialize(**opts)
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@opts = opts
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end
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def convert(data)
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raise InvalidData, '不合法的Base64数据' unless valid_base64?(data)
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io = StringIO.new(Base64.decode64(image_data data))
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raise OutLimit, '文件大小超过限制' if opts[:max_size].present? && io.size > opts[:max_size]
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raise InvalidFormat, '无效的格式' unless Image.new(io).image?
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io
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end
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private
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def valid_base64?(data)
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data&.start_with?(BASE64_HEAD)
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end
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def image_data(data)
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data[BASE64_HEAD.size..-1]
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end
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def size_limit
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EduSetting.find_by_name('upload_avatar_max_size')&.value
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end
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class Image
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attr_reader :io
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def initialize(io)
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raise ArgumentError unless io.respond_to?(:read)
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@io = io
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end
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def data
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@_data ||= begin
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data = io.read(9)
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io.rewind
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data
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end
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end
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def image?
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bitmap? || gif? || jpeg? || png?
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end
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def bitmap?
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data[0,2] == 66.chr + 77.chr
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end
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def gif?
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data[0,4] == 71.chr + 73.chr + 70.chr + 56.chr
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end
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def jpeg?
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data[0,3] == 0xff.chr + 0xd8.chr + 0xff.chr
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end
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def png?
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data[0,2] == 0x89.chr + 80.chr
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end
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end
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end |