Python PIL：如何使PNG中的区域透明？
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Python PIL: how to make area transparent in PNG?
提问by Hoff
I've been using PIL to crop Images, now I also want to make certain rectangular areas transparent, say
我一直在使用 PIL 来裁剪图像，现在我也想让某些矩形区域透明，比如
from PIL import Image
im = Image.open("sample.png")
transparent_area = (50,80,100,200)
...
I'd really appreciate some code as I haven't been able to find it, thanks a lot in advance!
我真的很感激一些代码，因为我找不到它，非常感谢！
Cheers,
干杯，
Hoff
霍夫
采纳答案by unutbu
from PIL import Image
from PIL import ImageDraw
im = Image.open("image.png")
transparent_area = (50,80,100,200)
mask=Image.new('L', im.size, color=255)
draw=ImageDraw.Draw(mask)
draw.rectangle(transparent_area, fill=0)
im.putalpha(mask)
im.save('/tmp/output.png')
I learned how to do this here.
回答by kindall
No source code, but this is the general approach that should work: Create an alpha channel for the image in "L" (grayscale) mode as a separate image object. Fill the alpha channel with white (full opacity) and draw the rectangle on the alpha channel image in black (full transparency). Convert the image to which you want to apply the transparency to RGBA and use the image object putalpha()method to copy the alpha channel you created into the image's alpha channel. Save as PNG.
没有源代码，但这是应该起作用的一般方法：在“L”（灰度）模式下为图像创建一个 alpha 通道作为单独的图像对象。用白色（完全不透明）填充 Alpha 通道，并用黑色（完全透明）在 Alpha 通道图像上绘制矩形。将要应用透明度的图像转换为 RGBA，并使用图像对象putalpha()方法将您创建的 alpha 通道复制到图像的 alpha 通道中。另存为 PNG。
