CS 140 - Quiz 5 Review Questions

1. Write a function named totalRed that takes a parameter pic and computes and returns the total of the red values that are even in pic. Run your function on the image bug.jpg and print that total to the terminal (use a print statement).

   import pygame
   
   # Compute the total amount of redness in an image
   # for the red values that are even
   def totalRed(pic):
       total = 0
       for y in range(pic.get_height()):
           for x in range(pic.get_width()):
               color = pic.get_at((x,y))
               if color.r % 2 == 0:
                   total = total + color.r
                   
       return total
                  
   # m a i n   p r o g r a m
   pygame.init()
   win = pygame.display.set_mode((1,1))
   basedir = "/home/ehar/t/Harcourt/gallery/"
   file = basedir + "bug.jpg"
   pic = pygame.image.load(file).convert()
   print "Total red is", totalRed(pic)
   pygame.quit()
       

2. The luminosity of an image is the total sum of its red, green, and blue components in all of the pixels. The average luminosity is the luminosity divided by the number of pixels in the image. Write a python program that computes the average luminosity of an image. Compare the luminosity of the image skulls.jpg and wave.jpg.

   import pygame
   
   # Compute the average luminosity of an image
   def avg_luminosity(pic):
       total = 0
       for y in range(pic.get_height()):
           for x in range(pic.get_width()):
               color = pic.get_at((x,y))
               total = total + color.r + color.g + color.b
                   
       return float(total)/(pic.get_width() * pic.get_height())
                  
   # m a i n   p r o g r a m
   pygame.init()
   win = pygame.display.set_mode((1,1))
   basedir = "/home/stlawu/ehar/t/Harcourt/gallery/"
   
   # compare the luminosity of the two images below
   file1 = basedir + "skulls.jpg"
   file2 = basedir + "wave.jpg"
   pic1 = pygame.image.load(file1)
   pic2 = pygame.image.load(file2)
   
   print "----------------------------------------------------------------"
   print
   print "The luminosity of", file1, "is", round(avg_luminosity(pic1),1)
   print
   print "The luminosity of", file2, "is", round(avg_luminosity(pic2), 1)
   print
   print "----------------------------------------------------------------"
   pygame.quit()
   

3. Assume we have two files image1.jpg and image2.jpg and that image1.jpg is smaller in both width and height than image2.jpg. Write a python program that creates a new image by centering image1.jpg inside of image2.jpg. For example, in the image below comic.jpg is centered in bug.jpg.
   
   Hint: This program does not need any loops or if-statements, just use the blit function.

   import pygame
   
   # This program centers one image inside
   # another.
   base = "/home/ehar/t/Harcourt/gallery/"
   image1 = base + "comic.jpg"
   image2 = base + "bug.jpg"
   pic1 = pygame.image.load(image1)
   pic2 = pygame.image.load(image2)
   
   # get the width and height of the images
   wpic1 = pic1.get_width()
   hpic1 = pic1.get_height()
   wpic2 = pic2.get_width()
   hpic2 = pic2.get_height()
   
   win=pygame.display.set_mode((wpic2,hpic2))
   
   # blit the first image in the second
   pic2.blit(pic1, ((wpic2-wpic1)/2, (hpic2-hpic1)/2))
   
   # now put the result on the display window
   win.blit(pic2, (0,0))
   pygame.display.update()
   raw_input("hit enter")
   pygame.quit()
   

4. The programming language in the comic above is called C. Based on the Python you know what do you think the program on the blackboard does?

   Prints I will not throw paper airlpanes in class 500 times.