C++ 访问 OpenCV 中的每个单独通道
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Access to each separate channel in OpenCV
提问by iampat
I have an image with 3 channels (img) and another one with a single channel (ch1).
我有一个带有 3 个通道 (img) 的图像和另一个带有单个通道 (ch1) 的图像。
Mat img(5,5,CV_64FC3);
Mat ch1 (5,5,CV_64FC1);
Is there any efficient way (not using for loop) to copy the first channel of imgto ch1?
是否有任何有效的方法（不使用 for 循环）将img的第一个通道复制到ch1？
采纳答案by Jacek
There is a function called cvMixChannels. You'll need to see implementation in the source code, but I bet it is well optimized.
有一个名为cvMixChannels的函数。您需要在源代码中查看实现，但我敢打赌它已得到很好的优化。
回答by orielfrigo
In fact, if you just want to copy one of the channels or split the color image in 3 different channels, CvSplit()is more appropriate (I mean simple to use).
事实上，如果你只是想复制其中一个通道或将彩色图像拆分为 3 个不同的通道，CvSplit()则更合适（我的意思是简单易用）。
Mat img(5,5,CV_64FC3);
Mat ch1, ch2, ch3;
// "channels" is a vector of 3 Mat arrays:
vector<Mat> channels(3);
// split img:
split(img, channels);
// get the channels (dont forget they follow BGR order in OpenCV)
ch1 = channels[0];
ch2 = channels[1];
ch3 = channels[2];
回答by techguy18985
You can use split function and then put zeros to the channels u want to ignore. This will result dispalying one channels out of three. See below..
您可以使用拆分功能，然后将零放在您想要忽略的通道上。这将导致显示三个频道中的一个。见下文..
For example:
例如：
Mat img, chans[3];
img = imread(.....); //make sure its loaded with an image
//split the channels in order to manipulate them
split(img, chans);
//by default opencv put channels in BGR order , so in your situation you want to copy the first channel which is blue. Set green and red channels elements to zero.
chans[1]=Mat::zeros(img.rows, img.cols, CV_8UC1); // green channel is set to 0
chans[2]=Mat::zeros(img.rows, img.cols, CV_8UC1);// red channel is set to 0
//then merge them back
merge(chans, 3, img);
//display
imshow("BLUE CHAN", img);
cvWaitKey();
回答by Gralex
You can access to specific channel, it works faster that splitoperation
您可以访问特定频道，split操作 速度更快
Mat img(5,5,CV_64FC3);
Mat ch1;
int channelIdx = 0;
extractChannel(img, ch1, channelIdx); // extract specific channel
// or extract them all
vector<Mat> channels(3);
split(img, channels);
cout << channels[0].size() << endl;
回答by jmartel
A simpler one if you have a RGB with 3 channels is cvSplit() if i'm not wrong, you have less to configure... (and i think it is also well optimized).
如果你有一个带有 3 个通道的 RGB，一个更简单的方法是 cvSplit() 如果我没有错的话，你需要配置的更少......（我认为它也得到了很好的优化）。
I would use cvMixChannel() for "harder" tasks... :p (i know i am lazy).
我会使用 cvMixChannel() 来完成“更难”的任务...... :p（我知道我很懒）。
