from cImage import *

def scaleDown(oldImage,xscale,yscale):
    '''Returns a new image scaled down (by integer ratios) from the oldImage'''
    oldW = oldImage.getWidth()
    oldH = oldImage.getHeight()
    newW = oldW//xscale
    newH = oldH//yscale
    newImage = EmptyImage(newW,newH)
    for newRow in range(newH):
        for newCol in range(newW):
            oldPixels = [oldImage.getPixel(xscale*newCol+dx,yscale*newRow+dy) for dx in range(xscale) for dy in range(yscale)]
            newImage.setPixel(newCol,newRow,
                              averagePixel(oldPixels))
    return newImage

def mean(values):
    return sum(values)/len(values)

def averagePixel(pixels):
    return Pixel(mean([pixel.getRed() for pixel in pixels]),
                 mean([pixel.getGreen() for pixel in pixels]),
                 mean([pixel.getBlue() for pixel in pixels]))
    
def show(image):
    win = ImageWin('Image', image.getWidth(), image.getHeight())
    image.draw(win)
    win.exitOnClick()