C++ 如何将 OpenCV Mat 的所有像素设置为特定值？
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How to set all pixels of an OpenCV Mat to a specific value?
提问by Drew Noakes
I have an image of type CV_8UC1. How can I set all pixel values to a specific value?
我有一个类型的图像CV_8UC1。如何将所有像素值设置为特定值？
回答by herohuyongtao
For grayscale image:
cv::Mat m(100, 100, CV_8UC1); //gray m = Scalar(5); //used only Scalar.val[0]or
cv::Mat m(100, 100, CV_8UC1); //gray m.setTo(Scalar(5)); //used only Scalar.val[0]or
Mat mat = Mat(100, 100, CV_8UC1, cv::Scalar(5));For colored image (e.g. 3 channels)
cv::Mat m(100, 100, CV_8UC3); //3-channel m = Scalar(5, 10, 15); //Scalar.val[0-2] usedor
cv::Mat m(100, 100, CV_8UC3); //3-channel m.setTo(Scalar(5, 10, 15)); //Scalar.val[0-2] usedor
Mat mat = Mat(100, 100, CV_8UC3, cv::Scalar(5,10,15));
对于灰度图像：
cv::Mat m(100, 100, CV_8UC1); //gray m = Scalar(5); //used only Scalar.val[0]或者
cv::Mat m(100, 100, CV_8UC1); //gray m.setTo(Scalar(5)); //used only Scalar.val[0]或者
Mat mat = Mat(100, 100, CV_8UC1, cv::Scalar(5));对于彩色图像（例如 3 个通道）
cv::Mat m(100, 100, CV_8UC3); //3-channel m = Scalar(5, 10, 15); //Scalar.val[0-2] used或者
cv::Mat m(100, 100, CV_8UC3); //3-channel m.setTo(Scalar(5, 10, 15)); //Scalar.val[0-2] used或者
Mat mat = Mat(100, 100, CV_8UC3, cv::Scalar(5,10,15));
P.S.: Check out this threadif you further want to know how to set given channel of a cv::Matto a given value efficiently without changing other channels.
PS：如果您想进一步了解如何在不更改其他通道的情况下有效地将 a 的给定通道设置为给定值，请查看此线程cv::Mat。
回答by Drew Noakes
The assignment operator for cv::Mathas been implemented to allow assignment of a cv::Scalarlike this:
cv::Mat已经实现了赋值运算符，以允许cv::Scalar像这样赋值：
// Create a greyscale image
cv::Mat mat(cv::Size(cols, rows), CV_8UC1);
// Set all pixel values to 123
mat = cv::Scalar::all(123);
The documentationdescribes:
该文档描述：
Mat& Mat::operator=(const Scalar& s)
s – Scalar assigned to each matrix element. The matrix size or type is not changed.
Mat& Mat::operator=(const Scalar& s)
s – 分配给每个矩阵元素的标量。矩阵大小或类型不会改变。
回答by Haris
In another way you can use
以另一种方式，您可以使用
Like
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Mat src(480,640,CV_8UC1);
src.setTo(123); //assign 123
