annotations/Azaion.Annotator/DTO/Label.cs

using System.Drawing;
using System.Globalization;
using System.IO;
using Newtonsoft.Json;
using Size = System.Windows.Size;

namespace Azaion.Annotator.DTO;

public abstract class Label
{
    [JsonProperty(PropertyName = "cl")] public int ClassNumber { get; set; }

    protected Label()
    {
    }

    protected Label(int classNumber)
    {
        ClassNumber = classNumber;
    }
}

public class CanvasLabel : Label
{
    public double X { get; set; }
    public double Y { get; set; }
    public double Width { get; set; }
    public double Height { get; set; }
    public double? Probability { get; }

    public CanvasLabel()
    {
    }

    public CanvasLabel(int classNumber, double x, double y, double width, double height, double? probability = null) : base(classNumber)
    {
        X = x;
        Y = y;
        Width = width;
        Height = height;
        Probability = probability;
    }

    public CanvasLabel(YoloLabel label, Size canvasSize, Size videoSize, double? probability = null)
    {
        var cw = canvasSize.Width;
        var ch = canvasSize.Height;
        var canvasAr = cw / ch;
        var videoAr = videoSize.Width / videoSize.Height;

        ClassNumber = label.ClassNumber;

        var left = label.CenterX - label.Width / 2;
        var top = label.CenterY - label.Height / 2;

        if (videoAr > canvasAr) //100% width
        {
            var realHeight = cw / videoAr; //real video height in pixels on canvas
            var blackStripHeight = (ch - realHeight) / 2.0; //height of black strips at the top and bottom

            X = left * cw;
            Y = top * realHeight + blackStripHeight;
            Width = label.Width * cw;
            Height = label.Height * realHeight;
        }
        else //100% height
        {
            var realWidth = ch * videoAr; //real video width in pixels on canvas
            var blackStripWidth = (cw - realWidth) / 2.0; //height of black strips at the top and bottom

            X = left * realWidth + blackStripWidth;
            Y = top * ch;
            Width = label.Width * realWidth;
            Height = label.Height * ch;
        }
        Probability = probability;
    }
}

public class YoloLabel : Label
{
    [JsonProperty(PropertyName = "x")] public double CenterX { get; set; }

    [JsonProperty(PropertyName = "y")] public double CenterY { get; set; }

    [JsonProperty(PropertyName = "w")] public double Width { get; set; }

    [JsonProperty(PropertyName = "h")] public double Height { get; set; }

    public YoloLabel()
    {
    }

    public YoloLabel(int classNumber, double centerX, double centerY, double width, double height) : base(classNumber)
    {
        CenterX = centerX;
        CenterY = centerY;
        Width = width;
        Height = height;
    }

    public RectangleF ToRectangle() =>
        new((float)(CenterX - Width / 2.0), (float)(CenterY - Height / 2.0), (float)Width, (float)Height);

    public YoloLabel(CanvasLabel canvasLabel, Size canvasSize, Size videoSize)
    {
        var cw = canvasSize.Width;
        var ch = canvasSize.Height;
        var canvasAr = cw / ch;
        var videoAr = videoSize.Width / videoSize.Height;

        ClassNumber = canvasLabel.ClassNumber;

        double left, top;
        if (videoAr > canvasAr) //100% width
        {
            left = canvasLabel.X / cw;
            Width = canvasLabel.Width / cw;
            var realHeight = cw / videoAr; //real video height in pixels on canvas
            var blackStripHeight = (ch - realHeight) / 2.0; //height of black strips at the top and bottom
            top = (canvasLabel.Y - blackStripHeight) / realHeight;
            Height = canvasLabel.Height / realHeight;
        }
        else //100% height
        {
            top = canvasLabel.Y / ch;
            Height = canvasLabel.Height / ch;
            var realWidth = ch * videoAr; //real video width in pixels on canvas
            var blackStripWidth = (cw - realWidth) / 2.0; //height of black strips at the top and bottom
            left = (canvasLabel.X - blackStripWidth) / realWidth;
            Width = canvasLabel.Width / realWidth;
        }

        CenterX = left + Width / 2.0;
        CenterY = top + Height / 2.0;
    }

    public static YoloLabel? Parse(string s)
    {
        if (string.IsNullOrEmpty(s))
            return null;

        var strings = s.Replace(',', '.').Split(' ');
        if (strings.Length != 5)
            throw new Exception("Wrong labels format!");

        var res = new YoloLabel
        {
            ClassNumber = int.Parse(strings[0], CultureInfo.InvariantCulture),
            CenterX = double.Parse(strings[1], CultureInfo.InvariantCulture),
            CenterY = double.Parse(strings[2], CultureInfo.InvariantCulture),
            Width = double.Parse(strings[3], CultureInfo.InvariantCulture),
            Height = double.Parse(strings[4], CultureInfo.InvariantCulture)
        };
        return res;
    }

    public static async Task<List<YoloLabel>> ReadFromFile(string filename, CancellationToken cancellationToken = default)
    {
        var str = await File.ReadAllTextAsync(filename, cancellationToken);

        return str.Split('\n')
            .Select(Parse)
            .Where(ann => ann != null)
            .ToList()!;
    }

    public static async Task WriteToFile(IEnumerable<YoloLabel> labels, string filename, CancellationToken cancellationToken = default)
    {
        var labelsStr = string.Join(Environment.NewLine, labels.Select(x => x.ToString()));
        await File.WriteAllTextAsync(filename, labelsStr, cancellationToken);
    }

    public override string ToString() => $"{ClassNumber} {CenterX:F5} {CenterY:F5} {Width:F5} {Height:F5}".Replace(',', '.');
}

public class Detection : YoloLabel
{
    public Detection(YoloLabel label, double? probability = null)
    {
        ClassNumber = label.ClassNumber;
        CenterX = label.CenterX;
        CenterY = label.CenterY;
        Height = label.Height;
        Width = label.Width;
        Probability = probability;
    }
    public double? Probability { get; set; }
}