Flip horizontally an image in Python (JES)

Question

I need to make a function that will copy an image, but mirrored. I created the code to mirror the image, but it isn't working and I don't know why because I traced the code and it should be mirroring the image. Here's the code:

def invert(picture):
 width = getWidth(picture)
 height = getHeight(picture)

 for y in range(0, height):
   for x in range(0, width):
    sourcePixel = getPixel(picture, x, y)
    targetPixel = getPixel(picture, width - x - 1, height - y - 1)
    color = getColor(sourcePixel)
    setColor(sourcePixel, getColor(targetPixel))
    setColor(targetPixel, color)
 show(picture)
 return picture 

def main():
  file = pickAFile()
  picture = makePicture(file)
  newPicture = invert(picture)
  show(newPicture)

Can someone explain to me what is wrong? Thank you.

Answer 1

Try this :

def flip_vert(picture):
    width = getWidth(picture)
    height = getHeight(picture)

    for y in range(0, height/2):
        for x in range(0, width):
            sourcePixel = getPixel(picture, x, y)
            targetPixel = getPixel(picture, x, height - y - 1)
            color = getColor(sourcePixel)
            setColor(sourcePixel, getColor(targetPixel))
            setColor(targetPixel, color)

    return picture 


def flip_horiz(picture):
    width = getWidth(picture)
    height = getHeight(picture)

    for y in range(0, height):
        for x in range(0, width/2):
            sourcePixel = getPixel(picture, x, y)
            targetPixel = getPixel(picture, width - x - 1, y)
            color = getColor(sourcePixel)
            setColor(sourcePixel, getColor(targetPixel))
            setColor(targetPixel, color)

    return picture 

Answer 2

The problem is that you are looping across the whole image instead of only half of width. You mirror twice your image and get the same image as output as the one you input.

if you mirror across the Y axes the code should be

for y in range(0, height):
for x in range(0, int(width / 2)):