把灰度 Mat 图像中的一块区域填成零（或者其他常数值），最有效的方法是什么？
应该先创建全零图像，再调用 copyTo()，还是有更好的办法？
What would be the most efficient approach for filling one area within a grayscale Mat image with zeros (or, indeed, with another constant value)?
Is making an image of zeros and calling copyTo() the right approach, or does something better exist?
// read the picture
cv::Mat frame = cv::imread("sample-gray.jpg", CV_LOAD_IMAGE_COLOR);
// choose the area to modify
cv::Mat region = frame(cv::Rect(12, 12, 24, 24));
// give that area an rgb colour
region.setTo(cv::Scalar(blueChannel, greenChannel, redChannel));I'd choose setTo() (http://docs.opencv.org/modules/core/doc/basic_structures.html?highlight=setto#Mat&%20Mat%3a%3asetTo%28InputArray%20value,%20InputArray%20mask%29), like this:
// read the picture
cv::Mat frame = cv::imread("sample-gray.jpg", CV_LOAD_IMAGE_COLOR);
// choose the area to modify
cv::Mat region = frame(cv::Rect(12, 12, 24, 24));
// give that area an rgb colour
region.setTo(cv::Scalar(blueChannel, greenChannel, redChannel));假设要在白色画布上画一个黑色矩形。
cv::Mat canvas(120,120,CV_8U,cv::Scalar(255));
canvas(cv::Rect(18,18,24,48)) = 0;
cv::imshow("Img",canvas);
cv::waitKey();Suppose a white canvas gets a rectangle painted black on it:
cv::Mat canvas(120,120,CV_8U,cv::Scalar(255));
canvas(cv::Rect(18,18,24,48)) = 0;
cv::imshow("Img",canvas);
cv::waitKey();试试这段代码
Mat frame;
frame = imread("images/sample-gray.jpg");
int left=120;int top=120; int width=120;int height=120;
Rect region = Rect(left,top,width,height);
frame(region).setTo(cv::Scalar(0,0,0));
imshow("display",frame);Give this snippet a try
Mat frame;
frame = imread("images/sample-gray.jpg");
int left=120;int top=120; int width=120;int height=120;
Rect region = Rect(left,top,width,height);
frame(region).setTo(cv::Scalar(0,0,0));
imshow("display",frame);我通过 Java Mail API 发送消息。邮件到达后，收件箱显示的是发件地址。我想用一些文本替代这个地址。这应该是可以的，因为我收到的 facebook 邮件在收件箱里显示 "Facebook - Message title"，而不是 "mail…
我的 CRM 代码在网页资源中运行，所以要获取实体数据，就得写成 这样来读取数据。 可惜用 typescript 编写时，这个表达式无法编译。现在我手动把 window.parent 加到 Xrm.Page 前面……（Xrm 类型定义已经装好了），这…
我想发送一个 Date 响应头。所需的格式如下。 这是我目前尝试的代码。
