opencv python统计及绘制直方图的方法

cv2.calcHist(images, channels, mask, histSize, ranges[, hist[, accumulate]])

hist,bins = np.histogram(img.ravel(),256,[0,256])

import cv2
import numpy as np
from matplotlib import pyplot as plt

img = cv2.imread('/home/yc/Pictures/cat.jpg',0)
plt.hist(img.ravel(),256,[0,256]);
plt.show()

import cv2
import numpy as np
from matplotlib import pyplot as plt
img = cv2.imread('/home/yc/Pictures/cat.jpg',1)
color = ('b','g','r')
for i,col in enumerate(color):
  histr = cv2.calcHist([img],[i],None,[256],[0,256])
  plt.plot(histr,color = col)
  plt.xlim([0,256])
plt.show()

import sys
import numpy as np
import cv2
import matplotlib.pyplot as plt

def main():
  img=cv2.imread('/home/yc/Pictures/cat.jpg',0)
  #得到计算灰度直方图的值
  xy=xygray(img)  

  #画出灰度直方图
  x_range=range(256)
  plt.plot(x_range,xy,"r",linewidth=2,c='black')
  #设置坐标轴的范围
  y_maxValue=np.max(xy)
  plt.axis([0,255,0,y_maxValue])
  #设置坐标轴的标签
  plt.xlabel('gray Level')
  plt.ylabel("number of pixels")
  plt.show()

def xygray(img):
  #得到高和宽
  rows,cols=img.shape
  #存储灰度直方图
  xy=np.zeros([256],np.uint64)
  for r in range(rows):
    for c in range(cols):
      xy[img[r][c]] += 1
  #返回一维ndarry
  return xy

main()