使用PIL使所有白色像素透明？

I'm trying to make all white pixels transparent using the Python Image Library. (I'm a C hacker trying to learn python so be gentle) I've got the conversion working (at least the pixel values look correct) but I can't figure out how to convert the list into a buffer to re-create the image. Here's the code

我正在尝试使用Python Image Library使所有白色像素透明。（我是一个C黑客，试图学习python，所以要温柔）我已经有转换工作（至少像素值看起来正确）但我无法弄清楚如何将列表转换为缓冲区重新创建图片。这是代码

img = Image.open('img.png')
imga = img.convert("RGBA")
datas = imga.getdata()

newData = list()
for item in datas:
    if item[0] == 255 and item[1] == 255 and item[2] == 255:
        newData.append([255, 255, 255, 0])
    else:
        newData.append(item)

imgb = Image.frombuffer("RGBA", imga.size, newData, "raw", "RGBA", 0, 1)
imgb.save("img2.png", "PNG")

3 个解决方案

#1

You need to make the following changes:

您需要进行以下更改：

append a tuple (255, 255, 255, 0) and not a list [255, 255, 255, 0]
追加元组（255,255,255,0）而不是列表[255,255,255,0]
use img.putdata(newData)
使用img.putdata（newData）

This is the working code:

这是工作代码：

from PIL import Image

img = Image.open('img.png')
img = img.convert("RGBA")
datas = img.getdata()

newData = []
for item in datas:
    if item[0] == 255 and item[1] == 255 and item[2] == 255:
        newData.append((255, 255, 255, 0))
    else:
        newData.append(item)

img.putdata(newData)
img.save("img2.png", "PNG")

#2

You can also use pixel access mode to modify the image in-place:

您还可以使用像素访问模式来就地修改图像：

from PIL import Image

img = Image.open('img.png')
img = img.convert("RGBA")

pixdata = img.load()

width, height = image.size
for y in xrange(height):
    for x in xrange(width):
        if pixdata[x, y] == (255, 255, 255, 255):
            pixdata[x, y] = (255, 255, 255, 0)

img.save("img2.png", "PNG")

#3

import Image
import ImageMath

def distance2(a, b):
    return (a[0] - b[0]) * (a[0] - b[0]) + (a[1] - b[1]) * (a[1] - b[1]) + (a[2] - b[2]) * (a[2] - b[2])

def makeColorTransparent(image, color, thresh2=0):
    image = image.convert("RGBA")
    red, green, blue, alpha = image.split()
    image.putalpha(ImageMath.eval("""convert(((((t - d(c, (r, g, b))) >> 31) + 1) ^ 1) * a, 'L')""",
        t=thresh2, d=distance2, c=color, r=red, g=green, b=blue, a=alpha))
    return image

if __name__ == '__main__':
    import sys
    makeColorTransparent(Image.open(sys.argv[1]), (255, 255, 255)).save(sys.argv[2]);

#1