libfacedetection.net

This project is based on libfacedetection implementation. A .NET wrapper calls native implementations compiled for RIDs win-x86, win-x64 and linux-x64

Live demo

Getting started

In order to start to use the library, install the NuGet package first.

dotnet add package libfacedetection.net

Create an instance of CnnFaceDetector and call the Detect method with a Bitmap (System.Drawing).

// Load Bitmap
var bitmap = new Bitmap("file.jpg");

// Detect faces
var detector = new LibFaceDetection.CnnFaceDetector();
var result = detector.Detect(bitmap);

// Print rectangles
foreach (LibFaceDetection.CnnFaceDetected r in result)
{
    Console.WriteLine(r.Rectangle);
}

The CnnFaceDetected object contains also a Confidence property. You can use it to filter out found faces that could be some false positive.

Please note that original bitmap is converted internally in BGR format, thus after Detect call, your original bitmap will be compromised. Do not use it for further operations.

Performances

For a better performance keep an instance of CnnFaceDetector for multiple usage, but please note that the class is not thread safety. Do not use it concurrently from multiple threads. You can use ObjectPool available into Microsoft.Extensions.ObjectPool package to create a pool of available CnnFaceDetector instances. Please checkout a sample here.

You can also speedup the detection using a smaller image. You can downscale on your own, before passing it to the Detect method, or you can use an overload which accepts the maximum allowed image size.

var result = detector.Detect(bitmap, new Size(400, 400));

The library resizes the bitmap mantaining aspect ratio. The result contains faces with rectangles relative to the original bitmap. The right bitmap size depends on the accurrancy you need. Smaller image means faster detection, but lower quality, and viceversa.

Other image library integration

You are not bound to use Sytem.Drawing. If you want to use other libraries, like MagicScaler, ImageSharp, FreeImage, the Detect method has an overloads which accepts a pointer to the raw bitmap. You have also to pass image size and stride. Raw bitmap must be in BGR (better) or RGB format (a boolean allows to convert automatically), with a 8bit color depth.

Credits

Thanks nostromo117 for the logo