Compute maximum font size to fit image (https://stackoverflow.com/questions/62608763/measure-font-to-fit-text-into-specific-width)

Program.cs

using System;
using System.Collections.Generic;
using System.Drawing;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            string fontFamilyName = "Arial";

            int minFontSize = 10;
            int maxFontSize = 200;

            var fm = new FontMeasure(fontFamilyName, minFontSize, maxFontSize);

            // Create test images for many width/height combinations
            for(int width = 100; width < 300; width += 20)
            {
                for(int height = 100; height < 300; height += 20)
                {
                    // Test input
                    string input = "1188yyyiiiii_Š_?!mmmm";

                    // Allocate image, add light background to better highlight image size
                    using var img = new Bitmap(width, height);
                    using var g = Graphics.FromImage(img);
                    g.Clear(Color.LightYellow);

                    // Get correctly sized font
                    var font = fm.GetFont(input, g, width, height);

                    // Render
                    g.DrawString(input, font, Brushes.Black, 0, 0);

                    //img.Save($"img_{width}_{height}.png");
                }
            }
        }
    }

    class FontMeasure
    {
        int _minFontSize;
        int _maxFontSize;
        Dictionary<int, Font> _fontCache = new Dictionary<int, Font>();

        public FontMeasure(string fontFamily, int minFontSize, int maxFontSize)
        {
            _minFontSize = minFontSize;
            _maxFontSize = maxFontSize;

            // Cache all potentially needed font sizes
            for(int i = minFontSize; i <= maxFontSize; ++i)
                _fontCache.Add(i, new Font(fontFamily, i));
        }

        public Font GetFont(string str, Graphics g, int imgWidth, int imgHeight)
        {
            int counter = 0;

            // Measure with maximum sized font
            var baseSize = g.MeasureString(str, _fontCache[_maxFontSize]);
            ++counter;

            // Downsample to actual image size
            float widthRatio = imgWidth / baseSize.Width;
            float heightRatio = imgHeight / baseSize.Height;
            float minRatio = Math.Min(widthRatio, heightRatio);
            int estimatedFontSize = (int)(_maxFontSize * minRatio);

            // Make sure the precomputed font list is always hit
            if(estimatedFontSize > _maxFontSize)
                estimatedFontSize = _maxFontSize;
            else if(estimatedFontSize < _minFontSize)
                estimatedFontSize = _minFontSize;

            // Make sure the estimated size is not too large
            var estimatedSize = g.MeasureString(str, _fontCache[estimatedFontSize]);
            ++counter;
            bool estimatedSizeWasReduced = false;
            while(estimatedSize.Width > imgWidth || estimatedSize.Height > imgHeight)
            {
                if(estimatedFontSize == _minFontSize)
                    break;
                --estimatedFontSize;
                estimatedSizeWasReduced = true;

                estimatedSize = g.MeasureString(str, _fontCache[estimatedFontSize]);
                ++counter;
            }

            // Can we increase the size a bit?
            if(!estimatedSizeWasReduced)
            {
                while(estimatedSize.Width < imgWidth && estimatedSize.Height < imgHeight)
                {
                    if(estimatedFontSize == _maxFontSize)
                        break;
                    ++estimatedFontSize;

                    estimatedSize = g.MeasureString(str, _fontCache[estimatedFontSize]);
                    ++counter;
                }

                // We increase the size until it is larger than the image, so we need to go back one step afterwards
                if(estimatedFontSize > _minFontSize)
                    --estimatedFontSize;
            }

            Console.WriteLine("Calls to g.MeasureString(): " + counter);

            return _fontCache[estimatedFontSize];
        }
    }
}