Dynamically resizing font to fit space while using Graphics.DrawString

Question

Does anyone have a tip whereas you could dynamically resize a font to fit a specific area? For example, I have an 800x110 rectangle and I want to fill it with the max size font that would support the entire string I'm trying to display.

Bitmap bitmap = new Bitmap(800, 110);

using (Graphics graphics = Graphics.FromImage(bitmap))
using (Font font1 = new Font("Arial", 120, FontStyle.Regular, GraphicsUnit.Pixel))
{
    Rectangle rect1 = new Rectangle(0, 0, 800, 110);

    StringFormat stringFormat = new StringFormat();
    stringFormat.Alignment = StringAlignment.Center;
    stringFormat.LineAlignment = StringAlignment.Center;

    graphics.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
    graphics.DrawString("Billy Reallylonglastnameinstein", font1, Brushes.Red, rect1, stringFormat);
} 

bitmap.Save(Server.MapPath("~/Fonts/" + System.Guid.NewGuid() + ".png"));

Obviously that whole name won't render in the space provided at the large font size. There has to be a simple way to do this?

Answer 1

You should do a scale transform on Font.Size the following function is an example of doing that but you can improve it to apply better results.

Here is FindFont function which get a room and a text with prefered size and gives you a font in which you can set that whole text fits the room!

// This function checks the room size and your text and appropriate font
//  for your text to fit in room
// PreferedFont is the Font that you wish to apply
// Room is your space in which your text should be in.
// LongString is the string which it's bounds is more than room bounds.
private Font FindFont(
   System.Drawing.Graphics g,
   string longString,
   Size Room,
   Font PreferedFont
) {
   // you should perform some scale functions!!!
   SizeF RealSize = g.MeasureString(longString, PreferedFont);
   float HeightScaleRatio = Room.Height / RealSize.Height;
   float WidthScaleRatio = Room.Width / RealSize.Width;

   float ScaleRatio = (HeightScaleRatio < WidthScaleRatio)
      ? ScaleRatio = HeightScaleRatio
      : ScaleRatio = WidthScaleRatio;

   float ScaleFontSize = PreferedFont.Size * ScaleRatio;

   return new Font(PreferedFont.FontFamily, ScaleFontSize);
}

For your question you can call it like the following code:

Bitmap bitmap = new Bitmap(800, 110);

using (System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(bitmap))
using (Font font1 = new Font("Arial", 120, FontStyle.Regular, GraphicsUnit.Pixel))
{
   Rectangle rect1 = new Rectangle(0, 0, 800, 110);

   StringFormat stringFormat = new StringFormat();
   stringFormat.Alignment = StringAlignment.Center;
   stringFormat.LineAlignment = StringAlignment.Center;
   graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;

   Font goodFont = FindFont(graphics, "Billy Reallylonglastnameinstein", rect1.Size, font1);

   graphics.DrawString(
      "Billy Reallylonglastnameinstein",
      goodFont,
      Brushes.Red,
      rect1,
      stringFormat
   );
}

Answer 2

I've adapted Saeed's great function to more suit my requirements. Comments explain all:

    // You hand this the text that you need to fit inside some
    // available room, and the font you'd like to use.
    // If the text fits nothing changes
    // If the text does not fit then it is reduced in size to
    // make it fit.
    // PreferedFont is the Font that you wish to apply
    // FontUnit is there because the default font unit is not
    // always the one you use, and it is info required in the
    // constructor for the new Font.
    public static void FindGoodFont(Graphics Graf, string sStringToFit,
                                    Size TextRoomAvail, 
                                    ref Font FontToUse,
                                    GraphicsUnit FontUnit)
    {
        // Find out what the current size of the string in this font is
        SizeF RealSize = Graf.MeasureString(sStringToFit, FontToUse);
        Debug.WriteLine("big string is {0}, orig size = {1},{2}",
                         sStringToFit, RealSize.Width, RealSize.Height);
        if ((RealSize.Width <= TextRoomAvail.Width) && (RealSize.Height <= TextRoomAvail.Height))
        {
            Debug.WriteLine("The space is big enough already");
            // The current font is fine...
            return;
        }

        // Either width or height is too big...
        // Usually either the height ratio or the width ratio
        // will be less than 1. Work them out...
        float HeightScaleRatio = TextRoomAvail.Height / RealSize.Height;
        float WidthScaleRatio = TextRoomAvail.Width / RealSize.Width;

        // We'll scale the font by the one which is furthest out of range...
        float ScaleRatio = (HeightScaleRatio < WidthScaleRatio) ? ScaleRatio = HeightScaleRatio : ScaleRatio = WidthScaleRatio;
        float ScaleFontSize = FontToUse.Size * ScaleRatio;

        Debug.WriteLine("Resizing with scales {0},{1} chose {2}",
                         HeightScaleRatio, WidthScaleRatio, ScaleRatio);

        Debug.WriteLine("Old font size was {0}, new={1} ",FontToUse.Size,ScaleFontSize);

        // Retain whatever the style was in the old font...
        FontStyle OldFontStyle = FontToUse.Style;

        // Get rid of the old non working font...
        FontToUse.Dispose();

        // Tell the caller to use this newer smaller font.
        FontToUse = new Font(FontToUse.FontFamily,
                                ScaleFontSize,
                                OldFontStyle,
                                FontUnit);
    }

Answer 3

I don't want to bash against saaeds solution which is probably pretty awesome, too. But I found another one on msdn: Dynamic Graphic Text Resizing which worked for me.

public Font GetAdjustedFont(Graphics GraphicRef, string GraphicString, Font OriginalFont, int ContainerWidth, int MaxFontSize, int MinFontSize, bool SmallestOnFail)
{
   // We utilize MeasureString which we get via a control instance           
   for (int AdjustedSize = MaxFontSize; AdjustedSize >= MinFontSize; AdjustedSize--)
   {
      Font TestFont = new Font(OriginalFont.Name, AdjustedSize, OriginalFont.Style);

      // Test the string with the new size
      SizeF AdjustedSizeNew = GraphicRef.MeasureString(GraphicString, TestFont);

      if (ContainerWidth > Convert.ToInt32(AdjustedSizeNew.Width))
      {
       // Good font, return it
         return TestFont;
      }
   }

   // If you get here there was no fontsize that worked
   // return MinimumSize or Original?
   if (SmallestOnFail)
   {
      return new Font(OriginalFont.Name,MinFontSize,OriginalFont.Style);
   }
   else
   {
      return OriginalFont;
   }
}

Answer 4

This is just an update for @Saeed's FindFont function.

GraphicsUnit.Pixel needs to be added to FindFont function return line. Without GraphicsUnit.Pixel, system dpi will effect the drawn string. Problem will arise when the dpi of system and bitmap mismatches. You can see more detail in this Windows DPI setting affects Graphics.DrawString. Since GraphicsUnit of PreferedFont is already set to GraphicsUnit.Pixel and return font is not set with GraphicsUnit.Pixel. In this case text will go out of the Room dimension, if bitmap dpi is larger than system dpi and font size will go smaller than the expected size if bitmap dpi is smaller than system dpi. Here is the updated function.

    private Font FindFont(  System.Drawing.Graphics g , string longString , Size Room , Font PreferedFont)
    {
        SizeF RealSize = g.MeasureString(longString, PreferedFont);
        float HeightScaleRatio = Room.Height / RealSize.Height;
        float WidthScaleRatio = Room.Width / RealSize.Width;
        float ScaleRatio = (HeightScaleRatio < WidthScaleRatio) ? ScaleRatio = HeightScaleRatio : ScaleRatio = WidthScaleRatio;
        float ScaleFontSize = PreferedFont.Size * ScaleRatio;
        return new Font(PreferedFont.FontFamily, ScaleFontSize,PreferedFont.Style,GraphicsUnit.Pixel);
    }