Draw a rectangle covering

# Draw a collection of rectangles.
from PIL import Image, ImageDraw

GRID_SIZE = 15
LINE_WIDTH = 2
OUT_FILE = "out.png"

def main():
    rects = map(lambda x: x if len(x) == 4 else x + (1,1), input())
    min_x, max_x, min_y, max_y = 0, 0, 0, 0
    for (x, y, w, h) in rects:
        min_x = min(min_x, x)
        max_x = max(max_x, x+w)
        min_y = min(min_y, y)
        max_y = max(max_y, y+h)
    width = max_x - min_x + 2
    height = max_y - min_y + 2
    im = Image.new("RGB", (GRID_SIZE*width, GRID_SIZE*height), "white")
    draw = ImageDraw.Draw(im)
    for x in range(1,width):
        for i in range(LINE_WIDTH):
            draw.line([GRID_SIZE*x+i,0,GRID_SIZE*x+i,im.size[1]], fill=(0,0,0))
    for y in range(1,height):
        for j in range(LINE_WIDTH):
            draw.line([0,GRID_SIZE*y+j,im.size[0],GRID_SIZE*y+j], fill=(0,0,0))
    for (x, y, w, h) in rects:
        draw.rectangle([(x-min_x+1)*GRID_SIZE+LINE_WIDTH,
                        (y-min_y+1)*GRID_SIZE+LINE_WIDTH,
                        (x+w-min_x+1)*GRID_SIZE-1,
                        (y+h-min_y+1)*GRID_SIZE-1], fill=(255,0,0))
    im = im.transpose(Image.FLIP_TOP_BOTTOM)
    im.save(OUT_FILE)

if __name__ == "__main__":
    main()