Rotating an Image 90 degrees

Question

def rotate_picture_90_left(img: Image) -> Image:
    """Return a NEW picture that is the given Image img rotated 90 degrees
    to the left.

    Hints:
    - create a new blank image that has reverse width and height
    - reverse the coordinates of each pixel in the original picture, img,
        and put it into the new picture
    """
    img_width, img_height = img.size
    pixels = img.load()  # create the pixel map
    rotated_img = Image.new('RGB', (img_height, img_width))
    pixelz = rotated_img.load()
    for i in range(img_width):
        for j in range(img_height):
            pixelz[i, j] = pixels[i, j]
    return rotated_img

I believe my code does not seem to work because of the new image I have created and the reverse width, length and reversing the coordinates in the original picture. How can I fix my code to rotate the image correctly?

Answer 1

You need to consider following logic when converting coordinates:

• y turning to x
• x turning to y but moving from end to start

Here is the code:

from PIL import Image

def rotate_picture_90_left(img: Image) -> Image:
    w, h = img.size
    pixels = img.load()
    img_new = Image.new('RGB', (h, w))
    pixels_new = img_new.load()
    for y in range(h):
        for x in range(w):
            pixels_new[y, w-x-1] = pixels[x, y]
    return img_new

Example:

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