from PIL import Image
from PIL import ImageDraw
from io import BytesIO
from urllib.request import urlopen
url = "https://i.ytimg.com/vi/W4qijIdAPZA/maxresdefault.jpg"
file = BytesIO(urlopen(url).read())
img = Image.open(file)
img = img.convert("RGBA")
draw = ImageDraw.Draw(img, "RGBA")
draw.rectangle(((0, 00), (img.size[0], img.size[1])), fill=(0,0,0,127))
img.save('dark-cat.jpg')
这给了我一个巨大的黑色正方形.我希望它是一个半透明的黑色正方形，上面有一只cat .有什么 idea 吗？
抱歉，我关于它是一个bug的 comments 是不正确的，所以...
您可以通过创建一个临时图像并使用Image.alpha_composite()来实现，如下面的代码所示.请注意，它支持除黑色以外的半透明正方形.
from PIL import Image, ImageDraw
from io import BytesIO
from urllib.request import urlopen
TINT_COLOR = (0, 0, 0) # Black
TRANSPARENCY = .25 # Degree of transparency, 0-100%
OPACITY = int(255 * TRANSPARENCY)
url = "https://i.ytimg.com/vi/W4qijIdAPZA/maxresdefault.jpg"
with BytesIO(urlopen(url).read()) as file:
img = Image.open(file)
img = img.convert("RGBA")
# Determine extent of the largest possible square centered on the image.
# and the image's shorter dimension.
if img.size[0] > img.size[1]:
shorter = img.size[1]
llx, lly = (img.size[0]-img.size[1]) // 2 , 0
else:
shorter = img.size[0]
llx, lly = 0, (img.size[1]-img.size[0]) // 2
# Calculate upper point + 1 because second point needs to be just outside the
# drawn rectangle when drawing rectangles.
urx, ury = llx+shorter+1, lly+shorter+1
# Make a blank image the same size as the image for the rectangle, initialized
# to a fully transparent (0% opaque) version of the tint color, then draw a
# semi-transparent version of the square on it.
overlay = Image.new('RGBA', img.size, TINT_COLOR+(0,))
draw = ImageDraw.Draw(overlay) # Create a context for drawing things on it.
draw.rectangle(((llx, lly), (urx, ury)), fill=TINT_COLOR+(OPACITY,))
# Alpha composite these two images together to obtain the desired result.
img = Image.alpha_composite(img, overlay)
img = img.convert("RGB") # Remove alpha for saving in jpg format.
img.save('dark-cat.jpg')
img.show()
以下是将其应用于测试图像的结果:
