Wrong text width using AWT

Question

I'm currently writing a new Karaoke-FX-Generator using Java. Now I have a problem with the implementation of the TextExtents-Function: It returns the wrong string bounds for the Subtitle file.

Here's an example:

The red rectangle represents the bounds of the string calculated by my program while the red background are the bounds calculated by xy-vsfilter.

Does anyone know how to fix that. I'm trying several hours and I still don't get any further.

---

This is the current implementation of the function.

/**
 * Calculates the text-extents for the given text in the specified
 * style.
 * @param style The style
 * @param text  The text
 * @return The extents of the text.
 */
public TextExtents getTextExtents(AssStyle style, String text) {
    // Reads the font object from the cache.
    Font font = this.getFont(style.getFontname(), style.isBold(), style.isItalic());

    // If the font is unknown, return null.
    if (font == null)
        return null;

    // Add the font size. (Note: FONT_SIZE_SCALE is 64)
    font = font.deriveFont((float) style.getFontsize() * FONT_SIZE_SCALE);

    // Returns other values like ascend, descend and ext-lead.
    LineMetrics metrics = font.getLineMetrics(text, this.ctx);

    // Calculate String bounds.
    Rectangle2D rSize = font.getStringBounds(text, this.ctx);

    // Returns the text-extents.
    return new TextExtents(
            rSize.getWidth() / FONT_SIZE_SCALE,
            rSize.getHeight() / FONT_SIZE_SCALE,
            metrics.getAscent() / FONT_SIZE_SCALE,
            metrics.getDescent() / FONT_SIZE_SCALE,
            metrics.getLeading() / FONT_SIZE_SCALE
    );
}

---

I partially solved the problem. LOGFONT.lfHeight and Java uses different unit for font sizes. As such, I had to convert the font-size of java to the "logical" units.

// I used this code to convert from pixel-size to "logical units"
float fontSize = 72F / SCREEN_DPI;      // SCREEN_DPI = 96

Now I only have small differences.