胡时刻程序适用于png而不适用于jpg

Question

我目前有两个代码。一个在黑色背景上生成50个彩色圆的随机图像，在黑色背景上生成一个彩色矩形的一个图像。大小和颜色各不相同。我当前正在使用Hu矩来查找包含矩形的图像。我遇到的问题是该程序出于某种原因仅适用于.png图片，而不适用于.jpg图片。 opencv读取这些文件的原因有什么区别？甚至可能是jpg图片，由于某些时刻等于零，它破坏了代码，所以当我尝试进行对数转换时，它不起作用。

 import glob
 import cv2
 import math
 import os
 pictures=(glob.glob("./*.png"))
 values=[]
 for i in pictures:   #goes through the pictures in the folder and calculates their hu moments
    img = cv2.imread(i, cv2.IMREAD_GRAYSCALE)
    z,img = cv2.threshold(img,128,255,cv2.THRESH_BINARY)
    moments = cv2.HuMoments(cv2.moments(img)).flatten()
    adjusted=[]
    print(moments)
    for j in moments: #log adjusts the moments so that they are easier to read
       try:
          adjusted.append(-1*math.copysign(1.0,j)*math.log10(abs(j)))
       except:
          print('')
    values.append(moments)
 average=[0,0,0,0,0,0,0]

 for i in values: #next two for loops find the average of the all of the hu moments
    for j in range(7):
       average[j]=average[j]+i[j]

 for i in range(7):
    average[i]=average[i]/51

 diff=[]
 for i in values: #finds the total difference for each hu moment and the average
    total=0
    for j in range(7):
       total=abs(i[j]-average[j])+total
       #print (total)
    diff.append(total)
 print (diff)
 candidate=diff.index(max(diff)) #finds which picture had the highest difference from average
 print(diff.index(max(diff)))
 print(pictures[candidate])
 img = cv2.imread(pictures[candidate]) #opens the image to show the sqaure image
 cv2.imshow("sqaure image", img)
 cv2.waitKey(0)

因此，如前所述，此代码仅适用于png图片，而不适用于jpg。有人知道为什么是这样吗？另外，如果您想要创建图像的程序，我也可以上传它。