118 lines
3.6 KiB
Ruby
118 lines
3.6 KiB
Ruby
class WatermarkService
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POINTSIZE = 20
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KERNING = 1.2
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ANGLE = 45
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FILL_COLOR = "rgba(0,0,0,0.4)"
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attr_reader :text
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attr_reader :text_length
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def initialize(text = Current.application_name)
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@text = " #{text} " # give more space around each occurence
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@text_length = @text.length
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end
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def process(file, output)
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metadata = image_metadata(file)
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return if metadata.blank?
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watermark_image(file, output, metadata)
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output
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end
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private
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def watermark_image(file, output, metadata)
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MiniMagick::Tool::Convert.new do |convert|
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setup_conversion_commands(convert, file)
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apply_watermark(convert, metadata)
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convert << output.to_path
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end
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end
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def setup_conversion_commands(convert, file)
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convert << file.to_path
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convert << "-pointsize"
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convert << POINTSIZE
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convert << "-kerning"
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convert << KERNING
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convert << "-fill"
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convert << FILL_COLOR
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convert << "-gravity"
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convert << "northwest"
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end
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# Parcourt l'image ligne par ligne et colonne par colonne en y apposant un filigrane
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# en alternant un décalage horizontal sur chaque ligne
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def apply_watermark(convert, metadata)
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stride_x, stride_y, initial_offsets_x, initial_offset_y = calculate_watermark_params
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0.step(by: stride_y, to: metadata[:height] + stride_y * 2).with_index do |offset_y, index|
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initial_offset_x = initial_offsets_x[index % 2]
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0.step(by: stride_x, to: metadata[:width] + stride_x * 2) do |offset_x|
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x = initial_offset_x + offset_x
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y = initial_offset_y + offset_y
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draw_text(convert, x, y)
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end
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end
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end
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def calculate_watermark_params
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# Approximation de la longueur du texte, qui marche bien pour les constantes par défaut
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char_width_approx = POINTSIZE / 2
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char_height_approx = POINTSIZE * 3 / 4
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# Dimensions du rectangle de texte
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text_width_approx = char_width_approx * text_length * Math.cos(ANGLE * (Math::PI / 180)).abs
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text_height_approx = char_width_approx * text_length * Math.sin(ANGLE * (Math::PI / 180)).abs + char_height_approx
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diagonal_length = Math.sqrt(text_width_approx**2 + text_height_approx**2)
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# Calcul des décalages entre chaque colonne et ligne
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# afin que chaque occurence "suive" la précédente
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stride_x = ((diagonal_length + char_width_approx) / Math.cos(ANGLE * (Math::PI / 180)))
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stride_y = text_height_approx
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initial_offsets_x = [0, (0 - stride_x / 2).round] # Motif de damier en alternant le décalage horizontal
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initial_offset_y = 0 - stride_y # Offset négatif pour mieux couvrir le nord ouest
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[stride_x.round, stride_y.round, initial_offsets_x, initial_offset_y.round]
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end
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def draw_text(convert, x, y)
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# A chaque insertion de texte, positionne le curseur, définit la rotation, puis réinitialise ces paramètres pour la prochaine occurence
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# Note: x and y can be negative value
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convert << "-draw"
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convert << "translate #{x},#{y} rotate #{-ANGLE} text 0,0 '#{text}' rotate #{ANGLE} translate #{-x},#{-y}"
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end
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def image_metadata(file)
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read_image(file) do |image|
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width = image.width
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height = image.height
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if rotated_image?(image)
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width, height = height, width
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end
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{ width: width, height: height }
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end
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end
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def read_image(file)
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image = MiniMagick::Image.new(file.to_path)
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if image.valid?
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yield image
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else
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Rails.logger.info "Skipping image analysis because ImageMagick doesn't support the file #{file}"
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nil
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end
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end
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def rotated_image?(image)
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['RightTop', 'LeftBottom'].include?(image["%[orientation]"])
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end
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end
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