Python像素操作返回灰色图像而不是倒置图像

Question

我正在为项目做一些原型代码。我正在使用枕头打开图像和其他一些小东西，但是我想使用像素值手动反转图像。我使用了二进制补码，希望将其取反。但是，当我显示最终图像时，它是一个纯灰色的正方形，而不是反转的颜色。我只使用了275像素乘以183像素的负鼠图片。知道为什么它显示灰色块而不显示反转图像吗？

#importing Image module

from PIL import Image
import numpy
#sets numpy to print out full array
numpy.set_printoptions(threshold=numpy.inf)


def twos_comp(val, bits):
    """compute the 2's complement of int value val"""
    if (val & (1 << (bits - 1))) != 0: # if sign bit is set e.g., 8bit: 128-255
    val = val - (1 << bits)        # compute negative value
return val


im = Image.open('possum.jpg')
#im.show()

data = numpy.asarray(im)
#print(data)
#print("FINISHED PRINTING")

#print('NOW PRINTING BINARY')
data_binary = numpy.unpackbits(data)
data_binary.ravel()

#print(data_binary)

#print('FINISHED PRINTING')

#getting string of binary array
binaryString = numpy.array2string(data_binary)
binaryString = ''.join(binaryString.split())
binaryString = binaryString[:-1]
binaryString = binaryString[1:]

#print("Binary String: " + binaryString)

out = twos_comp(int(binaryString,2), len(binaryString))

#print('Now printing twos:')
#print(out)


#formatting non-binary two's comp as binary
outBinary = "{0:b}".format(out)
#print('Now printing binary twos: ' + outBinary)


outBinary = outBinary.encode('utf-8')

a_pil_image = Image.frombytes('RGB', (275, 183), outBinary)

a_pil_image.show()

Answer 1

您可以使用PIL / Pillow轻松地反转：

from PIL import Image, ImageChops

# Load image from disk and ensure RGB
im = Image.open('lena.png').convert('RGB')

# Invert image and save to disk
res = ImageChops.invert(im)
res.save('result.png')

将莉娜变成否定莉娜：

---

或者，如果您想对此进行更多的数学计算：

from PIL import Image                                                                       
import numpy as np                                                                          

im = Image.open('lena.png').convert('RGB')                                                    

# Make Numpy array
imnp = np.array(im)                                                                         
# Invert
imnp = 255 - imnp                                                                           
# Save
Image.fromarray(imnp).save('result.png') 

如果您想象黑色图像由（0,0,0）表示而白色图像由（255,255,255）表示，则不难发现通过从255中减去而不是使用二进制补码来实现颜色反转