Question

This is a long shot, but does anyone know of an algorithm for estimating and categorising text width (for a variable width font) based on its contents?

For example, I’d like to know that iiiiiiii is not as wide as abcdefgh, which in turn is not as wide as WWWWWWWW, even though all three strings are eight characters in length.

This is actually an attempt to build some smarts into a string truncation method, which at the moment is correctly truncating a visually wide string, but is also unnecessarily truncating a visually narrow string, because both strings contain the same number of characters. It’s probably sufficient for the algorithm to categorise the input string as narrow, normal or wide and then truncate as appropriate.

This question isn’t really language-specific, but if there is an algorithm then I’ll implement it in Java. This is for a web application. I’m aware that there are answers on SO that deal with this problem using JavaScript to obtain the width of a containing div element, but I wondered if a server-side solution is possible.

Answer 1

Most GUI frameworks provide some way to calculate text metrics for fonts on given output devices.

Using java.awt.FontMetrics, for example, I believe you can do this:

import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics; 

public int measureText(Graphics g, String text) {
   g.setFont(new Font("TimesRoman", Font.PLAIN, 12));
   FontMetrics metrics = g.getFontMetrics();

   return metrics.stringWidth(text);
}

Not tested, but you get the idea.

---

Under .Net you can use the Graphics.MeasureString method. In C#:

private void MeasureStringMin(PaintEventArgs e)
{

    // Set up string.
    string measureString = "Measure String";
    Font stringFont = new Font("Arial", 16);

    // Measure string.
    SizeF stringSize = new SizeF();
    stringSize = e.Graphics.MeasureString(measureString, stringFont);

    // Draw rectangle representing size of string.
    e.Graphics.DrawRectangle(new Pen(Color.Red, 1), 0.0F, 0.0F, stringSize.Width, stringSize.Height);

    // Draw string to screen.
    e.Graphics.DrawString(measureString, stringFont, Brushes.Black, new PointF(0, 0));
}