OpenCV的.at<uchar>(cy,cx)在EmguCV中的等价写法及代码解析咨询

Hey there! Since you're new to C++ and OpenCV but already comfortable with C# and EmguCV, let's tackle your questions clearly.

1. Equivalent of OpenCV's at<uchar>(cy, cx) in EmguCV #

For your Image<Gray, byte> dst image, EmguCV offers two primary ways to access and modify pixel values that match OpenCV's at method behavior:

• High-performance access (best for loops or bulk operations): Use the Data property, which exposes a 3D array of the image's pixel data. Since this is a single-channel grayscale image, the channel index is always 0. The syntax aligns perfectly with OpenCV's row-first order (cy = row/y-coordinate first, then cx = column/x-coordinate):

  // Read the pixel value at (cy, cx)
  byte pixelIntensity = dst.Data[cy, cx, 0];
  
  // Write a new intensity value (e.g., set to white)
  dst.Data[cy, cx, 0] = 255;
  

• Simpler (but slower) access: Use the GetPixel and SetPixel helper methods. Note that these methods use x-coordinate first, then y-coordinate (opposite of the Data property and OpenCV's at):

  // Read the pixel value
  Gray pixel = dst.GetPixel(cx, cy);
  byte pixelIntensity = pixel.Intensity;
  
  // Write a new intensity value
  dst.SetPixel(cx, cy, new Gray(255));
  

2. Parsing the Original Code & EmguCV Implementation #

Let’s start with a common example of the C++ OpenCV code you’re referencing—something like this:

// Example: Set the pixel at row `cy`, column `cx` to full white (255)
dst.at<uchar>(cy, cx) = 255;

What this code does:

This line directly modifies the underlying pixel buffer of the grayscale image dst, setting the intensity of the pixel at row cy (vertical position) and column cx (horizontal position) to 255 (the maximum value for a uchar, resulting in white).

EmguCV Equivalent

To replicate this behavior with your Image<Gray, byte> dst in C#, use the high-performance Data approach for most cases (especially if you’re processing multiple pixels in a loop):

// Set pixel at (cy, cx) to white (same as the C++ example)
dst.Data[cy, cx, 0] = 255;

If you prefer more readable code and aren’t worried about performance for small operations, the SetPixel method works too:

dst.SetPixel(cx, cy, new Gray(255));

内容的提问来源于stack exchange，提问作者BorHunter