Mr Baumgarten

Computer Science teacher and self confessed geek

Python Pillow

Pillow is the Python library for image manipulation.

Install

sudo pip3 install pillow

Example code snippets

Resizing an image

from PIL import Image

def resize(source_filename, dest_filename, new_height):
    im = Image.open(source_filename)
    new_width = round(im.width * new_height / im.height)
    out = im.resize((new_width, new_height))
    out.save(dest_filename)

Background colour removal

from PIL import Image
from PIL import ImageFilter

def hex_to_rgb(value):
    """ Converts `#ffffff` to (255,255,255) """
    value = value.lstrip('#')
    r = int(value[:2], 16)
    g = int(value[2:4], 16)
    b = int(value[4:], 16)
    return (r,g,b)

def image_remove_background( source_filename, target_filename, background_color="#ffffff", sensitivity=25):
    """ sensitivity is out of 256 """
    img = Image.open(source_filename)  
    img = img.convert("RGBA")  
    remove_color = hex_to_rgb(background_color)
    pixdata = img.load()  
    for y in range(img.size[1]):  
        for x in range(img.size[0]):  
                r, g, b, a = img.getpixel((x, y))  
                if abs(remove_color[0]-r)<sensitivity and 
                    abs(remove_color[1]-g)<sensitivity and 
                    abs(remove_color[2]-b)<sensitivity:
                    pixdata[x, y] = (0, 0, 0, 0)  # make it transparent
    img2 = img.filter(ImageFilter.GaussianBlur(radius=1))  
    if target_filename[-4:].lower() in (".jpg", ".jpe"):
        target_filename = target_filename[:-4] + ".png"
    img2.save(target_filename, "PNG")  

Note: For a more accurate green screen style effect, look at this post on reddit. https://www.reddit.com/r/Python/comments/m68js/trying_to_write_a_very_simple_green_screen_code/c2yk6wx?utm_source=share&utm_medium=web2x

Conversions

def convert_pil_to_numpy( pil_image ):
    from PIL import Image
    import numpy as np
    im2arr = np.array(im)     # note: im2arr.shape will return height x width x channel
    return im2arr

def convert_numpy_to_pil( np_image ):
    from PIL import Image
    import numpy as np
    arr2im = Image.fromarray(im2arr)
    return arr2im

def convert_cv2_to_pil( cv2_image ):
    import cv2
    from PIL import Image
    cv2_image_rgb = cv2.cvtColor(cv2_image, cv2.COLOR_BGR2RGB)
    pil_image = Image.fromarray(cv2_image_rgb)
    return pil_image

def convert_pil_to_cv2( pil_image ):
    import cv2
    import numpy as np
    from PIL import Image
    cv2_image = cv2.cvtColor(np.array(pil_image), cv2.COLOR_RGB2BGR)
    return cv2_image

Reference