Python - compare two images

 
# PIL is a great python library for doing everything related to images 
 
# check out the other PIL and Image examples: 
#   Find and Label objects in Images l 
#   Find and outline the sun  
#   Replace or remove colors from an image  
#   Find the average RGB color for and image   
#   Determine an image's type (regardless of extension)  
 
 
# here is the zipped full source for this example  
from PIL import Image
import time
import sys
 
def compareTwoPics(picture_1, picture_2, step=20):
    step = int(step)
    if step < 1:
        step = 1
 
    percent_similar = 0.0
    percent_red = 0.0
    percent_green = 0.0
    percent_blue = 0.0
    percent_totalcolor = 0.0
 
 
    total_check_points = 0.0
    total_not_match = 0.0
    percent_similar = 0.0
 
    pic1_total_red = 0
    pic1_total_green = 0
    pic1_total_blue = 0
    pic1_total_color = 0
 
    pic2_total_red = 0
    pic2_total_green = 0
    pic2_total_blue = 0
    pic2_total_color = 0
 
    #print picture_1 
    #print picture_2 
 
    try:
        pic1 = Image.open(picture_1)
        pic2 = Image.open(picture_2)
    except:
        # tried to open an unsupported format!! 
        #print str(picture_1) + " is not a supported image format" 
        #print str(picture_2) + " is not a supported image format" 
        return -1.0, 0.0, 0.0, 0.0
 
    pic1_width = pic1.size[0]
    pic1_height = pic1.size[1]
 
    pic2_width = pic2.size[0]
    pic2_height = pic2.size[1]
 
 
    if pic1_width != pic2_width:
        print "\n widths must be the same \n" 
        sys.exit()
    if pic1_height != pic2_height:
        print "\n widths must be the same \n" 
        sys.exit()
 
 
    for x in range(0, pic1_width):
        for y in range(0, pic1_height):
 
            if x % step == 0:
                pic1_color = pic1.getpixel((x,y))
                pic2_color = pic2.getpixel((x,y))
 
                total_check_points += 3
 
                if pic1_color[0] != pic2_color[0]:
                    total_not_match += 1
                if pic1_color[1] != pic2_color[1]:
                    total_not_match += 1
                if pic1_color[2] != pic2_color[2]:
                    total_not_match += 1
 
                pic1_total_red += pic1_color[0]
                pic1_total_green += pic1_color[1]
                pic1_total_blue += pic1_color[2]
 
 
                pic2_total_red += pic2_color[0]
                pic2_total_green += pic2_color[1]
                pic2_total_blue += pic2_color[2]
 
                #print "     pic1 count: "+ str(pic1_total_red) 
                #print "     pic2 count: "+ str(pic2_total_red) 
 
 
 
    pic1_total_color = pic1_total_red + pic1_total_green + pic1_total_blue
    pic2_total_color = pic2_total_red + pic2_total_green + pic2_total_blue
 
 
    percent_similar = 1 - (total_not_match / total_check_points)
    percent_red = abs(float(pic2_total_red) / float(pic1_total_red))
    percent_green = abs(float(pic2_total_green) / float(pic1_total_green))
    percent_blue = abs(float(pic2_total_blue) / float(pic1_total_blue))
    percent_totalcolor = abs(float(pic2_total_color) / float(pic1_total_color))
 
    print '----' 
    print "total % comparible red:  " + str(percent_red)
    print "total % comparible green:" + str(percent_green)
    print "total % comparible blue: " + str(percent_blue)
    print "total % comparible:      " + str(percent_totalcolor)
    print "total pic1:              " + str(pic1_total_color)
    print "total pic2               " + str(pic2_total_color)
 
 
    return percent_similar, percent_totalcolor, pic1_total_color, pic2_total_color
 
 
 
if __name__ == '__main__':
    try:
        import psyco
        psyco.full()
    except ImportError:
        print "...installing psyco would provide additional performance" 
 
 
    thedetail = 20
    if len( sys.argv ) < 3:
        print "\n\n" 
        print "Usage: " + str(sys.argv[0]) + " <photo1.png> <photo2.png> [detail]" 
        print "" 
        print " - photo1.png and photo2.png are the photos you are comparing" 
        print " - detail is just a number.  The higher the number the faster" 
        print " and less detailed the comparison will be.  Default detail is 20" 
        print "" 
        print "example:" 
        print " # Highest quality comparison, slowest turn around" 
        print " " + str(sys.argv[0]) + " photo.png photo2.png 1" 
        print " " 
        print " # Low quality comparison, high turn around" 
        print " " + str(sys.argv[0]) + " photo.png photo2.png 100" 
        sys.exit()
    else:
        try:
            thedetail = sys.argv[3]
        except:
            thedetail = 20
 
        tt = time.time()
        print str(compareTwoPics(sys.argv[1], sys.argv[2], step=thedetail))
        print "execution seconds: " + str(time.time() - tt)