Question

I’m trying to crop a rectangular region of a video RGB. First i found the coordinates of head joint and with this coordinates i drew a rectangle over the RGB video. Now i want to show in another video just the image that is inside of the rentangle in the first image. Any help would be great.

video RGB is displayed in a “RGBvideo” Image Control.
cropped image i want to display in a “faceImage” Image Control

I’ve search online but couldn’t find a solution to it. I am confuse.

thank you so much

Answer 1

Welcome to Stack Overflow, please don’t ask the same question multiple times. With less popular tags like Kinect, it can take some time for people to answer (the tag only has 79 followers).

For simplicity, I’m going to assume you want to crop out a set size image (for example, 60×60 pixels out of the original 800×600). In your VideoFrameReady method, you get the PlanarImage from the event args. This PlanarImage has the bits field, which contains all of the RGB data for the image. With a little math, you can cut out a small chunk of that data and use it as a smaller image.

// update video feeds
void nui_VideoFrameReady(object sender, ImageFrameReadyEventArgs e)
{
    PlanarImage image = e.ImageFrame.Image;

    // Large video feed
    video.Source = BitmapSource.Create(image.Width, image.Height, 96, 96, PixelFormats.Bgr32, null, image.Bits, image.Width * image.BytesPerPixel);

    // X and Y coordinates of the smaller image, and the width and height of smaller image
    int xCoord = 100, yCoord = 150, width = 60, height = 60;

    // Create an array to copy data into
    byte[] bytes = new byte[width * height * image.BytesPerPixel];

    // Copy over the relevant bytes
    for (int i = 0; i < height; i++) 
    {
        for (int j = 0; j < width * image.BytesPerPixel; j++)
        {
            bytes[i * (width * image.BytesPerPixel) + j] = image.Bits[(i + yCoord) * (image.Width * image.BytesPerPixel) + (j + xCoord * image.BytesPerPixel)];
        }
    }

    // Create the smaller image
    smallVideo.Source = BitmapSource.Create(width, height, 96, 96, PixelFormats.Bgr32, null, bytes, width * image.BytesPerPixel);
}

Please make sure you understand the code, instead of just copy/pasting it. The two for loops are for basic array copying, with the number of bytes per pixel taken into account (4 for BGR32). Then you use that small subset of the original data to create a new BitmapSource. You’ll need to you can change the width/height as you see fit, and determine the X and Y coordinates from the head tracking.