将python中的PIL图像逐像素转换为灰度，仅留下一种颜色

Question

我正在尝试在python 3.4.2中将图像转换为灰度，但我想不理会所有“红色”像素

from numpy import *
from pylab import *
from PIL import Image
from PIL import ImageOps


def grayscale(picture):
    res = Image.new(picture.mode, picture.size)
    red = '150,45,45'                    # for now I'm just tyring
    x = red.split(",")                   # to change pixels with R value less than 150 
                                         #and G/B values greater than 45
    width, height = picture.size         #to greyscale 

   for i in range(0, width):
       for j in range(0, height):
           pixel = picture.getpixel((i, j))  #get a pixel
           pixelStr = str(pixel)
           pixelStr = pixelStr.replace('(', '').replace(')', '')
           pixelStr.split(",")                 #remove parentheses and split so we 
                                               #can convert the pixel into 3 integers


           #if its not specifically in the range of values we're trying to convert
           #we place the original pixel otherwise we convert the pixel to grayscale

           if not (int(pixelStr[0]) >= int(x[0]) and int(pixelStr[1]) <= int(x[1]) and int(pixelStr[2]) <= int(x[2])):
              avg = (pixel[0] + pixel[1] + pixel[2]) / 3
              res.putpixel((i, j), (int(avg), int(avg), int(avg)))
           else:
              res.putpixel(pixel)
return res

现在，这会将图像转换为灰度，但据我所知，它不会像我想的那样留下任何彩色像素，任何帮助/建议/替代方式来完成我的任务将不胜感激。

谢谢

Answer 1

因此，以防万一以后有人读到我的代码由于我的错误而无法正常工作

res.putpixel(pixel) 

应该一直抛出错误，因为我没有将像素放置在只显示颜色信息的位置。 因为它没有引发错误，所以我们实际上从未进入过else：语句。

向队友寻求帮助，我们将代码更改为：

from numpy import *
from PIL import Image

red_lower_threshold = 150
green_blue_diff_threshold = 50
def grayscale(picture):
   res = Image.new(picture.mode, picture.size)

   for i in range(0, picture.size[0]):
       for j in range(0, picture.size[1]):
           pixel = picture.getpixel((i, j))  #get a pixel
           red = pixel[0]
           green = pixel[1]
           blue = pixel[2]

           if (red > red_lower_threshold and abs(green - blue) < green_blue_diff_threshold):
               res.putpixel((i, j), pixel)
           else:
               avg = (pixel[0] + pixel[1] + pixel[2]) / 3
               res.putpixel((i, j), (int(avg), int(avg), int(avg)))

res.save('output.jpg')
return res

这不是完美的，但可行的解决方案