#----------------------------------------------------------------------
# Program to illustrate simple image processing
#
# Copyright (C) February 10, 2017 -- Dr. William T. Verts
#----------------------------------------------------------------------

def Main():
    Filename = pickAFile()
    Canvas = makePicture(Filename)
    show(Canvas)
    
    for Y in range(getHeight(Canvas)):        # Scan every line of the image
        for X in range(getWidth(Canvas)):     # Scan every pixel within a line
            PX = getPixel(Canvas, X, Y)       # Pick up a pointer to pixel at <X,Y>
            
            # Pick up the values of the current pixel
            R = getRed(PX)
            G = getGreen(PX)
            B = getBlue(PX)
            
            # Modify the current values (uncomment the
            # section for the desired effect). 
            
            # Brighten the Pixel
            # R = R + 20
            # G = G + 20
            # B = B + 20
            
            # Darken the Pixel
            # R = R - 20
            # G = G - 20
            # B = B - 20

            # Negate the Pixel
            # R = 255 - R
            # G = 255 - G
            # B = 255 - B

            # Convert to Gray Scale
            # Brightness = (R + G + B) / 3
            # R = Brightness
            # G = Brightness
            # B = Brightness
            
            # Convert to Black & White
            # Brightness = (R + G + B) / 3
            # if (Brightness > 128):
            #     R = 255
            #     G = 255
            #     B = 255
            # else:
            #     R = 0
            #     G = 0
            #     B = 0
                
            # Convert to 8-color RGB            
            # if (R > 128):
            #     R = 255
            # else:
            #     R = 0
            #
            # if (G > 92):
            #     G = 255
            # else:
            #     G = 0
            #
            # if (B > 128):
            #     B = 255
            # else:
            #     B = 0
                
            # Update the pixel with the new values
            setRed(PX,R)
            setGreen(PX,G)
            setBlue(PX,B)
            
        # Show the changes on screen after each line
        repaint(Canvas)
    return