C++ 如何将像素设置为 cv::Mat 对象中的值？
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How to set a pixel to a value in a cv::Mat object?
提问by A S
I need to set a single pixel in the Mat object to a certain value.
我需要将 Mat 对象中的单个像素设置为某个值。
How to do it?
怎么做？
I am using openCV 2.1 with visual studio 2010.
我在 Visual Studio 2010 中使用 openCV 2.1。
回答by Régis B.
If you are dealing with a uchar (CV_8U) matrix:
如果您正在处理 uchar (CV_8U) 矩阵：
mat.at<uchar>(row, column, channel) = val;
回答by Jeff T.
In fact, there are 4 kinds of methods to get/set a pixel value in a cv::Mat object as described in the OpenCV tutorial.
实际上，如OpenCV 教程中所述，有 4 种方法可以在 cv::Mat 对象中获取/设置像素值。
The one @Régis mentioned is called On-The-Fly RAin OpenCV tutorial. It's the most convenient but also time-consuming.
提到的@Régis在 OpenCV 教程中称为On-The-Fly RA。这是最方便的，但也是最耗时的。
Based on the tutorial's experiment, it also lists performance differences in all the 4 methods.
基于教程的实验，它还列出了所有 4 种方法的性能差异。
- Efficient Way 79.4717 milliseconds
- Iterator 83.7201 milliseconds
- On-The-Fly RA93.7878 milliseconds
- LUT function 32.5759 milliseconds
- 高效方式 79.4717 毫秒
- 迭代器 83.7201 毫秒
- 即时RA93.7878 毫秒
- LUT 函数 32.5759 毫秒
回答by Mona Jalal
Here's an example:
下面是一个例子：
vector<cv::Point3f> xyzBuffer;
cv::Mat xyzBuffMat = cv::Mat(307200, 1, CV_32FC3);
for (int i = 0; i < xyzBuffer.size(); i++) {
xyzBuffMat.at<cv::Vec3f>(i, 1, 0) = xyzBuffer[i].x;
xyzBuffMat.at<cv::Vec3f>(i, 1, 1) = xyzBuffer[i].y;
xyzBuffMat.at<cv::Vec3f>(i, 1, 2) = xyzBuffer[i].z;
}
