这只是一个正确掌握中心和尺寸的问题。
Determine the center of the spot where you want to crop
Determine the new size using the scale factor
Determine the bounding box of the cropped image
The following script should do the trick.
import os.path
from PIL import Image
def get_img_dir():
src_dir = os.path.dirname(__file__)
img_dir = os.path.join(src_dir, '..', 'img')
return img_dir
def open_img():
img_dir = get_img_dir()
img_name = 'amsterdam.jpg'
full_img_path = os.path.join(img_dir, img_name)
img = Image.open(full_img_path)
return img
def crop_image(img, xy, scale_factor):
'''Crop the image around the tuple xy
Inputs:
-------
img: Image opened with PIL.Image
xy: tuple with relative (x,y) position of the center of the cropped image
x and y shall be between 0 and 1
scale_factor: the ratio between the original image's size and the cropped image's size
center = (img.size[0] * xy[0], img.size[1] * xy[1])
new_size = (img.size[0] / scale_factor, img.size[1] / scale_factor)
left = max (0, (int) (center[0] - new_size[0] / 2))
right = min (img.size[0], (int) (center[0] + new_size[0] / 2))
upper = max (0, (int) (center[1] - new_size[1] / 2))
lower = min (img.size[1], (int) (center[1] + new_size[1] / 2))
cropped_img = img.crop((left, upper, right, lower))
return cropped_img
def save_img(img, img_name):
img_dir = get_img_dir()
full_img_path = os.path.join(img_dir, img_name)
img.save(full_img_path)
if __name__ == '__main__':
ams = open_img()
crop_ams = crop_image(ams, (0.50, 0.50), 0.95)
save_img(crop_ams, 'crop_amsterdam_01.jpg')
crop_ams = crop_image(ams, (0.25, 0.25), 2.5)
save_img(crop_ams, 'crop_amsterdam_02.jpg')
crop_ams = crop_image(ams, (0.75, 0.45), 3.5)
save_img(crop_ams, 'crop_amsterdam_03.jpg')
原始图像。
crop_amsterdam_01.jpg。
