SubtitleEdit/libse/TextDraw.cs

using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;

namespace Nikse.SubtitleEdit.Core
{
    public static class TextDraw
    {

        public static double GetFontSize(double fontSize)
        {
            return fontSize * 0.895d; // font rendered in video players like vlc/mpv are a little smaller than .net, so we adjust font size a bit down
        }

        public static void DrawText(Font font, StringFormat sf, GraphicsPath path, StringBuilder sb, bool isItalic, bool isBold, bool isUnderline, float left, float top, ref bool newLine, float leftMargin, ref int pathPointsStart)
        {
            var next = new PointF(left, top);

            if (path.PointCount > 0)
            {
                int k = 0;
                var list = (PointF[])path.PathPoints.Clone(); // avoid using very slow path.PathPoints indexer!!!
                for (int i = list.Length - 1; i >= 0; i--)
                {
                    if (list[i].X > next.X)
                    {
                        next.X = list[i].X;
                    }

                    k++;
                    if (k > 60 || i <= pathPointsStart && pathPointsStart != -1)
                    {
                        break;
                    }
                }
            }

            if (newLine)
            {
                next.X = leftMargin;
                newLine = false;
                pathPointsStart = path.PointCount;
            }

            var fontStyle = FontStyle.Regular;
            if (isItalic)
            {
                fontStyle |= FontStyle.Italic;
            }

            if (isBold)
            {
                fontStyle |= FontStyle.Bold;
            }

            if (isUnderline)
            {
                fontStyle |= FontStyle.Underline;
            }

            var fontSize = (float)GetFontSize(font.Size);
            try
            {
                path.AddString(sb.ToString(), font.FontFamily, (int)fontStyle, fontSize, next, sf);
            }
            catch
            {
                fontStyle = FontStyle.Regular;
                try
                {
                    path.AddString(sb.ToString(), font.FontFamily, (int)fontStyle, fontSize, next, sf);
                }
                catch
                {
                    path.AddString(sb.ToString(), new FontFamily("Arial"), (int)fontStyle, fontSize, next, sf);
                }
            }
            sb.Length = 0;
        }

        public static float MeasureTextWidth(Font font, string text, bool bold)
        {
            using (var sf = new StringFormat { Alignment = StringAlignment.Near, LineAlignment = StringAlignment.Near })
            {
                using (var path = new GraphicsPath())
                {
                    var sb = new StringBuilder(text);
                    bool newLine = false;
                    const int leftMargin = 0;
                    int pathPointsStart = -1;
                    DrawText(font, sf, path, sb, false, bold, false, 0, 0, ref newLine, leftMargin, ref pathPointsStart);
                    if (path.PathData.Points.Length == 0)
                    {
                        return 0;
                    }

                    float width = 0;
                    var list = (PointF[])path.PathPoints.Clone(); // avoid using very slow path.PathPoints indexer!!!
                    int max = list.Length;
                    if (max <= 500)
                    {
                        for (int i = 0; i < max; i++)
                        {
                            if (list[i].X > width)
                            {
                                width = list[i].X;
                            }
                        }
                        return width;
                    }

                    int interval = 1;
                    if (max > 1500)
                    {
                        interval = 5;
                    }
                    else if (max > 1000)
                    {
                        interval = 3;
                    }
                    else
                    {
                        interval = 2;
                    }
                    for (int i = 0; i < max; i += interval)
                    {
                        if (list[i].X > width)
                        {
                            width = list[i].X;
                        }
                    }
                    if (list[1].X > width)
                    {
                        width = list[1].X;
                    }
                    if (list[2].X > width)
                    {
                        width = list[2].X;
                    }
                    if (list[max - 1].X > width)
                    {
                        width = list[max - 1].X;
                    }
                    if (list[max - 2].X > width)
                    {
                        width = list[max - 2].X;
                    }

                    return width;
                }
            }
        }

        public static float MeasureTextHeight(Font font, string text, bool bold)
        {
            using (var sf = new StringFormat { Alignment = StringAlignment.Near, LineAlignment = StringAlignment.Near })
            {
                using (var path = new GraphicsPath())
                {
                    var sb = new StringBuilder(text);
                    bool newLine = false;
                    const int leftMargin = 0;
                    int pathPointsStart = -1;
                    DrawText(font, sf, path, sb, false, bold, false, 0, 0, ref newLine, leftMargin, ref pathPointsStart);

                    float height = 0;
                    var list = (PointF[])path.PathPoints.Clone(); // avoid using very slow path.PathPoints indexer!!!
                    int index = System.Math.Max(list.Length - 80, 0);
                    for (int i = index; i < list.Length; i += 2)
                    {
                        if (list[i].Y > height)
                        {
                            height = list[i].Y;
                        }
                    }

                    for (int i = 0; i < list.Length; i += 2)
                    {
                        if (list[i].Y > height)
                        {
                            height = list[i].Y;
                        }
                    }

                    return height;
                }
            }
        }

    }
}