PixQL: SQL for image processing(github.com)

  # Join image to itself but offset by one pixel and report the average of the RGB values
  SELECT (img1_pixel.red+img2_pixel.red)/2
         (img1_pixel.green+img2_pixel.green/2
         (img1_pixel.blue+img2_pixel.blue)/2
  FROM   img1 img1_pixel INNER JOIN img1 img2_pixel
         ON img1_pixel.column = img2_pixel.column
         AND img1_pixel.row = img2_pixel.row+1;

  # Superimpose one image over another, offset by 100 pixels width/height
  UPDATE img1, img2
  SET    img1.rgb = img2.rgb
  WHERE  img1.row = img2.row+100
         AND img1.column = img2.column;

    # turn all red pixels green
    # omitting column name assumes COLOR
    pixql -i in.bmp -o out.bmp -q "SELECT #00FF00FF WHERE COLOR = #FF0000FF;"
    
    # copy red channel into green channel
    pixql -i in.bmp -o out.bmp -q "SELECT R AS G;"
    
    # add white 1px 100x100 grid
    pixql -i in.bmp -o out.bmp -q "SELECT WHITE AS COLOR WHERE ROW % 100 = 0 OR COL % 100 = 0;"

    SELECT 255-R AS R, 255-G AS G, 255-B AS B
    FROM (SELECT WHITE WHERE ROW % 20 < 10 FROM BLACK(100,100))
    WHERE COL % 20 < 10;