在图像上绘制多个透明蒙版

Question

我有一个图像和一些二进制蒙版我想应用于图像以突出显示某些区域。我能够绘制一个蒙版，但每个后续应用的蒙版都会越来越多地使前一个蒙版和原始图像变亮。

如何在保持每个蒙版和图像亮度不变的情况下应用多个蒙版？

import numpy as np
import matplotlib
from matplotlib.pyplot import imshow
from PIL import Image, ImageDraw, ImageFont
import requests

matplotlib.rcParams['figure.figsize'] = (20.0, 10.0)

url = 'https://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Grumpy_Cat_by_Gage_Skidmore.jpg/480px-Grumpy_Cat_by_Gage_Skidmore.jpg'
image = (Image.open(requests.get(url, stream=True).raw)).convert('RGBA')

annotation1 = (np.ones((image.size[1], image.size[0], 3))*255).astype(np.uint8)
annotation1[350:400, 50:450] = (255, 0, 0)
mask1 = (np.zeros((image.size[1], image.size[0])))
mask1[350:400, 50:450] = 1
mask1 = Image.fromarray(mask1, mode='1')

annotation2 = (np.ones((image.size[1], image.size[0], 3))*255).astype(np.uint8)
annotation2[400:450, 50:450] = (255, 0, 0)
mask2 = (np.zeros((image.size[1], image.size[0])))
mask2[350:400, 50:450] = 1
mask2 = Image.fromarray(mask2, mode='1')

annotation1 = Image.fromarray(annotation1, mode='RGB').convert('RGBA')
annotation2 = Image.fromarray(annotation2, mode='RGB').convert('RGBA')
annotation1.putalpha(128)
annotation2.putalpha(128)

image = Image.alpha_composite(image, annotation1)
image = Image.alpha_composite(image, annotation2)
imshow(image)

我也尝试使用Image.composite()，但它只显示了蒙版和白色图像的其余部分。

image = Image.composite(image, annotation1, mask1)

Answer 1

您可以使用ImageDraw.bitmap(xy, bitmap, fill=None)从位图中绘制遮罩。每个蒙版可以有多个阴影，但只有一种颜色。

url = 'https://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Grumpy_Cat_by_Gage_Skidmore.jpg/480px-Grumpy_Cat_by_Gage_Skidmore.jpg'
image = (Image.open(requests.get(url, stream=True).raw)).convert('RGBA')
image.putalpha(128)

mask1 = (np.zeros((image.size[1], image.size[0]))).astype(np.uint8)
mask1[350:400, 50:450] = 255
mask1 = Image.fromarray(mask1, mode='L')

mask2 = (np.zeros((image.size[1], image.size[0]))).astype(np.uint8)
mask2[410:460, 50:450] = 255
mask2[415:455, 55:445] = 128
mask2 = Image.fromarray(mask2, mode='L')

overlay = Image.new('RGBA', image.size, (255,255,255,0))
drawing = ImageDraw.Draw(overlay)
drawing.bitmap((0, 0), mask1, fill=(255, 0, 0, 128))
drawing.bitmap((0, 0), mask2, fill=(255, 0, 0, 128))

image = Image.alpha_composite(image, overlay)

imshow(image)