CSC111 Lab 7 2014

--D. Thiebaut (talk) 12:45, 10 March 2014 (EDT)

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Page under construction!

Skeleton Program

# JES Picture processing
# D. Thiebaut
# A demo of some of the functions available in JES for manipulating 
# the pixels of an image.


# the image we are playing with
image = None

# changeColor( image ).
# Changes the amount of red, green and blue that is in an image
def changeColor( image ):
  for x in range(0,getWidth(image)):
    for y in range(0,getHeight(image)):
        pixel = getPixel (image, x, y)
        red   = getRed(pixel)
        green = getGreen(pixel)
        blue  = getBlue(pixel)
  
        # the line below replaces the pixel with its original color.  Change
        # the amount of red, green and blue to see some change in the colors
        newColor = makeColor( red, green, blue )
        setColor( pixel, newColor )
  return image

# ==================================================================  
#                             MAIN PROGRAM
# ==================================================================  
file = pickAFile()
image = makePicture( file ) 
show( image )
  
#image = changeColor( image )
#repaint( image )

Problem 1: random processing

Write a function (use the skeleton program for a skeleton function with nested for-loops) that modifies the red, green and blue components of each pixel.

Problem 2: black and white

• Make your image black and white by storing the same value in the green, red, and blue component of a pixel. In a first step, pick the amount of red of the pixel and store that number in the 3 components.

• Next take the average amount of red, green and blue and store that value (store it in a variable called grey for example), in all three components.

• Better: initial the grey variable as follows:

  grey  = int( 0.3 * red +0.6 * green +0.11 * blue )

Problem 3

Copy paste this function that contains a call to repaint( image ) inside the for x in range(...) loop. See how the program "sweeps" through the image.

• Modify the function so that the sweep goes from left to right.

• Modify the function so that the sweep goes from top to bottom

• Modify the function so that the sweep goes from bottom to top

Problem 4

Pick one of the functions you have written for the problems above and make a new copy of it under a different name.

Replace the nested for-loop with this loop:

    for x in range( getWidth( image ) ):
        for y in range( min( x, getHeight( image ) ):

Predict the way the image is going to be transformed by these nested for-loops. Then run it!

Problem 5: Border

Write a new function called addBorder( image, borderWidth ) that will put a red border around the image.

Modify the program and ask the user to pick a color first, then pass this color to the function addBorder( image, borderWidth, color ) which will put a border all around the image.

Problem 6: B&W image with Colored Border

Make your program output a version of your colored image that will be black and white with a colored border around it.

Problem 7: Diagonal

• Replace the nested for-loops by this single loop like this:

     for x in range(0,getWidth(image)): 
         y = min( x, getHeight( image )-1 )
         pixel = getPixel (image, x, y)
         ...

and set the color of that pixel to red. What do you get?

• Modify your function so that it puts a red diagonal cross over the image.