marking_photo

marking_photo.rb

# Watermarking image with another image using Imagemagick 'composite', 'watermark' and 'dissolve'.
require "rmagick"

Dir.entries("./target").each_slice(7) do |group|
  group.each do |target_photo|
    next if target_photo == "." || target_photo == ".."

    # This is necessary to don't explode your memory
    GC.start
    GC.disable

    # Read the image in the memory with RMagick
    img = Magick::Image.read("./target/#{target_photo}").first

    # the original image was in jpg format
    # need to make the white background color transparent
    # also changed the format to png since JPG does not support transparency.
    # run the command below to create an image with transparent background using ImageMagick
    # convert cc.png -transparent white -fuzz 2% watermark.png

    mark = Magick::Image.read("./watermark.png").first

    # set the canvas to transparent
    # if we do not specify 'background_color' on 'mark' then on rotation the background color will be black.
    # we want it to be transparent.
    mark.background_color = "Transparent"

    # resize the watermark to 60% of the image we want to watermark

    watermark = mark.resize_to_fit(img.rows * 0.3, img.columns * 0.3)

    # rotate this mark by 45 degrees anticlockwise (optional)
    # watermark.rotate!(-45)

    # using composite
    # place the watermark in the center of the image
    # default 'compose over' overlays the watermark on the background image
    # SoftLightCompositeOp darkens or lightens the colors, dependent on the source color value.
    # If the source color is lighter than 0.5, the destination is lightened.
    # If the source color is darker than 0.5, the destination is darkened, as if it were burned in.
    # The degree of darkening or lightening is proportional to the difference between the source color and 0.5.
    # If it is equal to 0.5, the destination is unchanged.
    # Painting with pure black or white produces a distinctly darker or lighter area, but does not result in pure black or white.
    img1 = img.composite(watermark, Magick::SouthEastGravity, Magick::HardLightCompositeOp)
    # save the watermarked image
    img1.write("./new-photos/#{target_photo}")

    # using watermark
    # place the watermark in the center of the image with gravity
    # watermark the image with 20% brightness and 30% saturation
    # img2 = img.watermark(watermark, 0.2, 0.3, Magick::CenterGravity)
    # save the watermarked image
    # img2.write("/home/aditya/Pictures/wm_old_england_pic_image_watermark.jpg")

    # using dissolve
    # add watermark with 40% opacity for watermark, 100% opacity for image and position is center
    # img3 = img.dissolve(watermark, 0.4, 1, Magick::CenterGravity)
    # save the watermarked image
    # img3.write("/home/aditya/Pictures/wm_old_england_pic_image_dissolve.jpg")
  end
end