15.6. Chapter 15 Exercises

Below is a selection of images that you can use in the programs in this section.

beach.jpg	baby.jpg	vangogh.jpg	swan.jpg

puppy.jpg	kitten.jpg	girl.jpg	motorcycle.jpg

gal1.jpg	guy1.jpg	gal2.jpg

Note

Remember that it can take a bit of time to process all the pixels in a picture! Check for errors below the code if it is taking a long time, but if you don’t see any errors just wait.

1. Make changes to 10 lines in the code below so that it runs. It changes areas that look red in the original to green.

   from import * # CREATE AN IMAGE FROM A FILE img = Image("gal2.jpg") # LOOP THROUGH ALL PIXELS for x in range(img.getWidth()): for y in range(img.getHeight()) p = img.getPixel(x, y) r = p.getRed() g = p.getGreen() b = p.getBlue() # VALUES FOR THE NEW COLOR if r > 200 and g < 100 and b < 100: # CREATE THE COLOR newPixel = Pixel(0, g, b) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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2. Fix the code below so that the red in the picture gets changed to blue.

   from image import * # CREATE AN IMAGE FROM A FILE img = Image("girl.jpg") # LOOP THROUGH ALL PIXELS for x in range(img.getWidth()): for y in range(img.getHeight()): p = img.getPixel(x, y) r = p.getRed() g = p.getGreen() b = p.getBlue() # VALUES FOR THE NEW COLOR if r < 150 and g > 100 and b > 100: # CREATE THE COLOR newPixel = Pixel(0, 0, 0) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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3. Fix the indention in the code below so that it runs correctly. It does a primitive form of edge detection by getting all of the pixels (except for the last row) and all the pixels to the right of those and determining if the difference between the average of the rgb values for the pixel and the pixel to the right are substantially different.

   from image import * # CREATE AN IMAGE FROM A FILE img = Image("swan.jpg") # LOOP THROUGH ALL BUT LAST COLUMN for x in range(img.getWidth() - 1): for y in range(img.getHeight()): p = img.getPixel(x, y) p2 = img.getPixel(x + 1, y) r1 = p.getRed() g1 = p.getGreen() b1 = p.getBlue() average1 = (r1 + g1 + b1) / 3 r2 = p2.getRed() g2 = p2.getGreen() b2 = p2.getBlue() average2 = (r2 + g2 + b2) / 3 # VALUES FOR THE NEW COLOR if abs(average2 - average1) > 10: newPixel = Pixel(0, 0, 0) else: newPixel = Pixel(255, 255, 255) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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4. Fix and change the code to change just the background color from white to gray.

   # CREATE AN IMAGE FROM A FILE img = Image("gal2.jpg") # LOOP THROUGH ALL PIXELS for x in range(img.getWidth()): for y in range(img.getHeight()): p = img.getPixel(x, y) r = p.getRed() g = p.getGreen() b = p.getBlue() # VALUES FOR THE NEW COLOR if r > 0 and g > 0 and b > 0: # CREATE THE COLOR newPixel = Pixel(100, 100, 100) # CHANGE THE IMAGE img.setPixel(x, y, p) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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5. Fix the indention in the code below so that it runs correctly. It posterizes a picture which means that it reduces all the colors in a picture to a small number of colors – like the ones you might use if you were making a poster..

   from image import * # CREATE AN IMAGE FROM A FILE img = Image("beach.jpg") # LOOP THROUGH ALL PIXELS for x in range(img.getWidth()): for y in range(img.getHeight()): p = img.getPixel(x, y) r = p.getRed() g = p.getGreen() b = p.getBlue() # VALUES FOR THE NEW COLOR if r < 120: r = 0 if r >= 120: r = 120 if g < 120: g = 0 if g >= 120: g = 120 if b < 120: b = 0 if b >= 120: b = 120 # CREATE THE COLOR newPixel = Pixel(r,g,b) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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6. Fix the indentation so that the code puts the motorcycle on the beach. The code checks if the pixel isn’t white in the first image, and if it’s not, it places that pixel in the same location on the second image.

   from image import * # CREATE THE IMAGES img1 = Image("motorcycle.jpg") img2 = Image("beach.jpg") width1 = img1.getWidth() height1 = img1.getHeight() width2= img2.getWidth() height2 = img2.getHeight() maxWidth = min(width1,width2) maxHeight = min(height1,height2) # LOOP THROUGH THE PIXELS for x in range(maxWidth): for y in range(maxHeight): p1 = img1.getPixel(x, y) r1 = p1.getRed() g1 = p1.getGreen() b1 = p1.getBlue() # CHECK IF THE PIXEL ISN'T WHITE if r1 < 250 and g1 < 250 and b1 < 250: # COPY THE COLOR TO IMG2 img2.setPixel(x, y, p1) # SHOW THE CHANGED IMAGE win = ImageWin(img2.getWidth(),img2.getHeight()) img2.draw(win)

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7. Fix 5 errors in the code below. It will copy the non-white pixels from gal1.jpg to guy1.jpg.

   from image import * # CREATE THE IMAGES img1 = Image("gal1.jpg") img2 = Image(guy1.jpg") # LOOP THROUGH ALL THE PIXELS IN IMG1 for x in range(img1.getWidth(): for y in range(img1.getHeight()) p1 = img1.getPixel(x, ) r1 = p1.getRed() g1 = p1.getGreen() b1 = p1.getBlue() # CHECK IF THE PIXEL ISN'T WHITE if r1 < 250 and g1 < 250 b1 < 250: # COPY THE COLOR TO IMG2 img2.setPixel(x, y, p1) # SHOW THE CHANGED IMAGE win = ImageWin(img2.getWidth(),img2.getHeight()) img2.draw(win)

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8. Fix the 5 errors so that a swan in shown on a beach.

   from image import * # CREATE THE IMAGES img1 = Image(swan.jpg) img2 = Image("beach.jpg") width1 = img1.getWidth() height1 = img1.getHeight() width2= img2.getWidth() height2 = img2.getHeight() maxWidth = min(width1,width2) maxHeight = min(height1,height2) # LOOP THROUGH THE PIXELS for x in range(maxWidth): for y in range(maxHeight): p1 = img1.getPixel() r1 = p1.getRed g1 = p1.getGreen() b1 = p1.getBlue() # CHECK IF THE PIXEL ISN'T WHITE if r1 > 100 and g1 > 100 and b1 > 100 # COPY THE COLOR TO IMG2 img2.setPixel(x, y, pixel) # SHOW THE CHANGED IMAGE win = ImageWin(img2.getWidth(),img2.getHeight()) img2.draw(win)

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9. Change the code below to use if and else rather than two if statements per color. It posterizes an image.

   from image import * # CREATE AN IMAGE FROM A FILE img = Image("beach.jpg") # LOOP THROUGH ALL PIXELS for x in range(img.getWidth()): for y in range(img.getHeight()): p = img.getPixel(x, y) r = p.getRed() g = p.getGreen() b = p.getBlue() # VALUES FOR THE NEW COLOR if r < 120: r = 0 if r >= 120: r = 120 if g < 120: g = 0 if g >= 120: g = 120 if b < 120: b = 0 if b >= 120: b = 120 # CREATE THE COLOR newPixel = Pixel(r,g,b) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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10. Fix the indentation in the code and change it so that it edges the motorcycle but the background is black and the motorcycle edging will be white.

    from image import * # CREATE AN IMAGE FROM A FILE img = Image("motorcycle.jpg") # LOOP THROUGH ALL BUT LAST COLUMN for x in range(img.getWidth() - 1): for y in range(img.getHeight()): p = img.getPixel(x, y) p2 = img.getPixel(x + 1, y) r1 = p.getRed() g1 = p.getGreen() b1 = p.getBlue() average1 = (r1 + g1 + b1) / 3 r2 = p2.getRed() g2 = p2.getGreen() b2 = p2.getBlue() average2 = (r2 + g2 + b2) / 3 # VALUES FOR THE NEW COLOR if abs(average2 - average1) > 10: newPixel = Pixel(0, 0, 0) else: newPixel = Pixel(255, 255, 255) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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11. Change the following code into a procedure. It posterizes an image. Be sure to call it to test it.

    from image import * # CREATE AN IMAGE FROM A FILE img = Image("beach.jpg") # LOOP THROUGH ALL PIXELS for x in range(img.getWidth()): for y in range(img.getHeight()): p = img.getPixel(x, y) r = p.getRed() g = p.getGreen() b = p.getBlue() # VALUES FOR THE NEW COLOR if r < 120: r = 0 if r >= 120: r = 120 if g < 120: g = 0 if g >= 120: g = 120 if b < 120: b = 0 if b >= 120: b = 120 # CREATE THE COLOR newPixel = Pixel(r,g,b) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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12. Fix the 5 errors in the procedure so that it edges the motorcycle which means the image should only have 2 colors. The motorcycle should be one color, everything else should be the other color.

    def edger(img): # LOOP THROUGH ALL BUT LAST COLUMN for x in range(img.getWidth() ): for y in range(img.getHeight()): p = img.getPixel(x, y) p2 = img.getPixel(x + 1, y) r1 = p.getRed() g1 = p.getGreen() b1 = p.getBlue() average1 = (r1 + g1 + b1) / 3 r2 = p2.getRed() g2 = p2.getGreen() b2 = p2.getBlue() average2 = (r2 + g2 + b2) / 3 # VALUES FOR THE NEW COLOR if abs(average2 - average1) > 10 newPixel = Pixel(0, 0, 0) else: newPixel = Pixel(255, 255, 255) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win) from image import * # CREATE AN IMAGE FROM A FILE img = Image(motorcycle.jpg) edger(img)

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13. Change the following into a procedure. It changes areas that are mostly red looking to green. Be sure to call it to test it.

    from image import * # CREATE AN IMAGE FROM A FILE img = Image("gal2.jpg") # LOOP THROUGH ALL PIXELS for x in range(img.getWidth()): for y in range(img.getHeight()): p = img.getPixel(x, y) r = p.getRed() g = p.getGreen() b = p.getBlue() # VALUES FOR THE NEW COLOR if r > 200 and g < 100 and b < 100: # CREATE THE COLOR newPixel = Pixel(0, g, b) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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14. The code below currently makes the picture gray. Change it so that it posterizes (reduce the number of colors) the image instead.

    from image import * # CREATE AN IMAGE FROM A FILE img = Image("kitten.jpg") # LOOP THROUGH ALL PIXELS for x in range(img.getWidth()): for y in range(img.getHeight()): p = img.getPixel(x, y) r = p.getRed() g = p.getGreen() b = p.getBlue() # VALUES FOR THE NEW COLOR if r < 120: r = 150 if r >= 120: r = 200 if g < 120: g = 150 if g >= 120: g = 200 if b < 120: b = 150 if b >= 120: b = 200 # CREATE THE COLOR newPixel = Pixel(r,g,b) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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15. Write the code to posterize a picture but use 3 values for each color instead of 2. Use 0 if the current value is less than 85, use 85 if the value is less than 170, else use 170.

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16. Fix the errors in the code and change the code to use if’s and else’s instead of just if’s.

    from image import * # CREATE AN IMAGE FROM A FILE img = Image("arch.jpg") # LOOP THROUGH ALL PIXELS for x in range(img.getWidth() for y in range(img.getHeight()): p = img.getPixels(x, y) r = p.getRed() g = p.getGreen() b = p.getBlue() # VALUES FOR THE NEW COLOR if r < 120: r = 0 if r >= 120: r = 120 if g < 120: g = 0 if g >= 120: g = 120 if b < 120: b = 0 if b >= 120: b = 120 # CREATE THE COLOR newPixel = Pixel(r,g,b) # CHANGE THE IMAGE img.setPixel(x, y, newPixel) # SHOW THE CHANGED IMAGE win = ImageWin(img.getWidth(),img.getHeight()) img.draw(win)

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17. Write the code to do edge detection on a picture, but compare the curent pixel with the one below it rather than the one to the right.

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18. Write a procedure that takes an image as a parameter and edges it using the colors blue and white.

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19. Write a procedure to remove the red on very red pixels (pixels that have a red value greater than 200 and a green and blue value of less than 100).

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20. Write a procedure that takes a picture as a parameter and converts all the red to grayscale.

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