annotations/Azaion.Annotator/DTO/Label.cs

using System.Globalization;
using System.Windows;
using Newtonsoft.Json;

namespace Azaion.Annotator.DTO;

public abstract class Label
{
    [JsonProperty(PropertyName = "cl")]
    public int ClassNumber { get; set; }
    
    public Label(){}
    public 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 CanvasLabel() { }
    public CanvasLabel(int classNumber, double x, double y, double width, double height) : base(classNumber)
    {
        X = x;
        Y = y;
        Width = width;
        Height = height;
    }

    public CanvasLabel(YoloLabel label, Size canvasSize, Size videoSize)
    {
        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;
        }
    }
}

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 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)
            return null;

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