CODEWITHSUNDEEP
c#
caine1337
caine1337

Reputation: 63

How do I draw a pixel at a specific position on a window?

I need to create a program that will display lines or dots of coordinates read from a txt file. The application will be attached to the output of an eye-tracking program, and will display the data.

How do I display some sort of graphic at a particular coordinate on the screen?

Note: The window is full-screen, and I can use WPF or WinForms.

Upvotes: 2

Views: 321

Answers (2)

BradleyDotNET
BradleyDotNET

Reputation: 61349

I would overlay your video with an Image element; something like:

<Grid>
   <Image x:Name=TrackingImage />
   <MediaElement/>
</Grid>

Then in your code behind; set the source to a WriteableBitmap. The documentation has an excellent sample, but to summarize it here:

WriteableBitmap writeableSource = new WriteableBitmap(100, 100, 96, 96, PixelFormats.Bgra32, null);

// Calculate the number of bytes per pixel. 
int _bytesPerPixel = (writeableSource .Format.BitsPerPixel + 7) / 8;
// Stride is bytes per pixel times the number of pixels.
// Stride is the byte width of a single rectangle row.
int _stride = writeableSource .PixelWidth * _bytesPerPixel;

private void SomeUpdateFunction()
{
     // Define the rectangle of the writeable image we will modify. 
     // The size is that of the writeable bitmap.
     Int32Rect _rect = new Int32Rect(0, 0, _wb.PixelWidth, _wb.PixelHeight);

    //Update writeable bitmap with the colorArray to the image.
    _wb.WritePixels(_rect, pixelBuffer, _stride, 0);
    TrackingImage.Source = writeableSource;
}

Note that it uses WritePixels (specifically; this overload: MSDN)

Obviously you will need to modify the parameters to get the correct pixel in the correct place. This is the right technique though.

This answer was inspired by: Drawing Pixels in WPF It might be worth looking at if you need more info.

Upvotes: 2

Jason Kleban
Jason Kleban

Reputation: 20778

Various bitmap formats are instructions to put colored dots at specific locations. Why not use something like that? What ELSE do you need it to do?

Regarding your eye-tracking and point-data comment, if you want to composite it with captured video, then you don't need to worry about how to display the images so much as you need to think about how to add the dots to the video itself. The video player will do the displaying.

From what I know about screen-capture and video codecs (not a whole lot) it will be best to work with the uncompressed video before it gets encoded. Otherwise you'll have to decode, add, and re-encode. I'd look for a way to hook into the capture program and add the live eye-tracker data to the captured frames.

Upvotes: 1

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