分離顏色分量

Question

我正在關注this發佈以查找圖像的顏色分量。我想我會從紅色組件開始，然後着手其他組件。我寫的代碼如下。我沒有使用Linux，我正在使用Windows。

#include <opencv\cv.h> 
#include <opencv2\imgproc\imgproc.hpp> 
#include <opencv2\highgui\highgui.hpp> 
#include <iostream> 
#include <stdio.h> 

using namespace std; 
using namespace cv; 

int main(int argc, char**argv) 
{ 
    IplImage* image=cvLoadImage("C:/Users/Administrator/Desktop/sample.png",1); 
    IplImage* red=cvCreateImage(cvSize(image->width, image->height), image->depth,image->nChannels); 
    uchar *pImg =(uchar*)image->imageData; 
    uchar *pRed=(uchar*)red->imageData; 
    for(int i=0;i<image->height;i++) 
    { 
     for(int j=0;j<image->width;j++) 
     { 
      red=pImg[i*image->widthStep + j*image->nChannels + 2]; 
      pRed[i*image->widthStep + j*image->nChannels + 2]=red; 
     } 
    } 
    namedWindow("Display",1); 
    cvShowImage("Display",red); 
    waitKey(0); 
    return 0; 
} 

線條

red=pImg[i*image->widthStep + j*image->nChannels + 2];

pRed[i*image->widthStep + j*image->nChannels + 2]=red;

都出現了這樣的錯誤：

A value of type uchar cannot be assigned to an entity of the type IplImage

我要去哪裏錯了？

Answer 1

使用C++：

cv::Mat myImage; 
myImage=imread("myImage.jpg"); 
std::vector<cv::Mat> channels; 
cv::split(myImage,channels); 
imshow("Red Channel",channels[2]); 

Answer 2

red這裏定義：

IplImage* red=cvCreateImage( ...

看起來你只是想要一個單獨的顏色值，所以你需要使用一個新的變量（我把它命名爲redValue，使其不易混淆）

for(int j=0;j<image->width;j++) 
    { 
     uchar redValue=pImg[i*image->widthStep + j*image->nChannels + 2]; 
     pRed[i*image->widthStep + j*image->nChannels + 2]=redValue; 
    } 

Answer 3

第一：如果不強制使用IplImage請切換到cv::Mat，因爲它是如此容易理解和使用的OpenCV新的C++語法！

對於你的問題：如果你想只提取紅色通道（手動就像你做的那樣，openCV可以用你的函數調用它），試試這個代碼：我已經添加了評論，

我使用這個作爲輸入圖像來進行測試：

#include <opencv\cv.h> 
#include <opencv2\imgproc\imgproc.hpp> 
#include <opencv2\highgui\highgui.hpp> 
#include <iostream> 
#include <stdio.h> 

using namespace std; 
using namespace cv; 

int main(int argc, char**argv) 
{ 
    IplImage* image=cvLoadImage("C:/Users/Administrator/Desktop/sample.png",1); 
    // !!! the image that shall contain the red channel must have number of channels = 1 !!! 
    IplImage* red=cvCreateImage(cvSize(image->width, image->height), image->depth,1); 
    uchar *pImg =(uchar*)image->imageData; 
    uchar *pRed=(uchar*)red->imageData; 
    for(int i=0;i<image->height;i++) 
    { 
     for(int j=0;j<image->width;j++) 
     { 
      // !!! you have to use a variable that holds the value of single channel's pixel, which is uchar in this case (values from 0 to 255) 
      uchar redVal=pImg[i*image->widthStep + j*image->nChannels + 2]; 
      // !!! since the red image has only 1 channel, be sure to use the right ->nChannels (from the 'red' image 
      pRed[i*red->widthStep + j*red->nChannels]=redVal; 
     } 
    } 
    namedWindow("Display",1); 
    cvShowImage("Display",red); 
    waitKey(0); 
    return 0; 
} 

這應該只顯示紅色通道作爲灰度圖像。

結果看起來像這樣的莉娜輸入圖像：

如果你想在RGB顯示，並關閉其他渠道試試這個：

#include <opencv\cv.h> 
#include <opencv2\imgproc\imgproc.hpp> 
#include <opencv2\highgui\highgui.hpp> 
#include <iostream> 
#include <stdio.h> 

using namespace std; 
using namespace cv; 

int main(int argc, char**argv) 
{ 
    IplImage* image=cvLoadImage("C:/Users/Administrator/Desktop/sample.png",1); 
    // !!! use 3 channels again because we want to display colors 
    IplImage* red=cvCreateImage(cvSize(image->width, image->height), image->depth,3); 
    uchar *pImg =(uchar*)image->imageData; 
    uchar *pRed=(uchar*)red->imageData; 
    for(int i=0;i<image->height;i++) 
    { 
     for(int j=0;j<image->width;j++) 
     { 
      // !!! you have to use a variable that holds the value of single channel's pixel, which is uchar in this case (values from 0 to 255) 
      uchar redVal=pImg[i*image->widthStep + j*image->nChannels + 2]; 
      // !!! set all channels to zero, except the red channel which is copied. be sure to use the right widthStep 
      pRed[i*red->widthStep + j*red->nChannels + 0]=0; 
      pRed[i*red->widthStep + j*red->nChannels + 1]=0; 
      pRed[i*red->widthStep + j*red->nChannels + 2]=redVal; 
     } 
    } 
    namedWindow("Display",1); 
    cvShowImage("Display",red); 
    waitKey(0); 
    return 0; 
} 

結果看起來像這樣的萊納輸入圖像：