问题是，正如您所说，您的图像是 ，因此在此行上：
if pixels[i,j] == (225, 225, 225):
没有像素会等于RGB三元组，(255,255,255)因为白色像素将仅仅是灰度值，255而不是RGB三元组。
如果将循环更改为：
if pixels[i,j] == 29:
pixels[i,j] = 1
elif pixels[i,j] == 179:
pixels [i,j] = 2
else:
pixels[i,j] = 0
这是对比结果：
您可能要考虑使用 “ Look Up Table” 或LUT进行转换，因为大量的if语句可能很笨拙。基本上，图像中的每个像素都会替换为一个新像素，该像素可以通过在表中查找其当前索引来找到。我也这样做很numpy有趣：
#!/usr/local/bin/python3
import numpy as np
from PIL import Image
# Open the input image
PILimage=Image.open("classified.png")
# Use numpy to convert the PIL image into a numpy array
npImage=np.array(PILimage)
# Make a LUT (Look-Up Table) to translate image values. Default output value is zero.
LUT=np.zeros(256,dtype=np.uint8)
LUT[29]=1 # all pixels with value 29, will become 1
LUT[179]=2 # all pixels with value 179, will become 2
# Transform pixels according to LUT - this line does all the work
pixels=LUT[npImage];
# Save resulting image
result=Image.fromarray(pixels)
result.save('result.png')
结果-拉伸对比度后：
上面我可能有点冗长，所以如果您喜欢更简洁的代码：
import numpy as np
from PIL import Image
# Open the input image as numpy array
npImage=np.array(Image.open("classified.png"))
# Make a LUT (Look-Up Table) to translate image values
LUT=np.zeros(256,dtype=np.uint8)
LUT[29]=1 # all pixels with value 29, will become 1
LUT[179]=2 # all pixels with value 179, will become 2
# Apply LUT and save resulting image
Image.fromarray(LUT[npImage]).save('result.png')
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