OpenCV之图像像素&图像色彩通道

一次OpenCV相关作业，有一个助教小姐姐写的tutorial，很有用，链接如下：

链接:http://pan.baidu.com/s/1bZHsJk  密码:854s

1. 色彩空间：

将RGB图像转换成ycrcb和hsv图像并保存每种色彩空间每个通道的图像。

import cv2
import numpy as np

img=cv2.imread('/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/rice_grains.jpg',cv2.IMREAD_COLOR)
hsv=cv2.cvtColor(img,cv2.COLOR_BGR2HSV)
ycrcb=cv2.cvtColor(img,cv2.COLOR_BGR2YCrCb)


R, G, B = cv2.split(img)
cv2.imwrite("/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/Red.jpg", R)
cv2.imwrite("/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/Green.jpg",G)
cv2.imwrite("/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/Blue.jpg",B)


H,S,V=cv2.split(hsv)
cv2.imwrite("/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/Hue.jpg",H)
cv2.imwrite("/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/Saturation.jpg",S)
cv2.imwrite("/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/Value.jpg",V)


Y,Cb,Cr=cv2.split(ycrcb)
cv2.imwrite("/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/Y.jpg",Y)
cv2.imwrite("/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/Cb.jpg",Cb)
cv2.imwrite("/Users/wangmengxi/Documents/mercy/ec601/openCV/ex2/rice_grains/Cr.jpg",Cr)

输入：

输出：

Blue:

Red:

Green:

Cb:

Cr:

Y:

Hue:

Saturation:

Value:

 分离通道：

R, G, B = cv2.split(img)

2. 计算图像像素：

下面代码是用来计算图像在（20，25）处的像素（分别是RGB, ycrcb和hsv通道的图）

#!/usr/bin/env python    
# encoding: utf-8    
  
import numpy as np  
import cv2  
  
baboon = cv2.imread("/Users/wangmengxi/Documents/mercy/ec601/openCV/OpenCV_homework/Test_images/baboon.jpg")
hsv=cv2.cvtColor(baboon,cv2.COLOR_BGR2HSV)
ycrcb=cv2.cvtColor(baboon,cv2.COLOR_BGR2YCrCb)
(b,g,r) = baboon[20,25]
(Cr,Cb,Y)=ycrcb[20,25]
(v,s,h)=hsv[20,25]
#print("baboon.jpg:")
print("BGR:")

print(b,g,r)

print("ycrcb:")

print(Cr,Cb,Y)

print("hsv:")
print(v,s,h)

注意：要把imread中的路径换成自己的图片路径

python版本：python2.7

输入：

输出：

问题：

 What are the ranges of pixel values in each channel of each of the above mentioned colorspaces?

value range of R,G,B : 0~255
value range of Y,U,V : 16~235,16~240,16~240
value range of H,S,V : 0~180,0~255,0~255
value range of L,A,B : 0~100,-127~127,-127~127
value range of C,M,Y,K : 0~100