Auto Font Size For Text (GD via PHP)

Question

There is a space of x*y for text to go on $im (GD Image Resource) how can I choose a font size (or write text such that) it does not overflow over that area?

Answer 1

I think you look for the imagettfbbox function.

I used that some years ago for a script generating localized buttons for a Web interface. I actually resized buttons if the text didn't fit in the template, to keep text size consistent, but you can try to reduce the text size until the text fits.

If you are interested, I can paste some snippets of my code (or give it right away).

[EDIT] OK, here is some extracts of my code, someday I will clean it up (make it independent of target app, give samples) and make it public as a whole.
I hope the snippets make sense.

// Bounding boxes: ImageTTFBBox, ImageTTFText:
// Bottom-Left: $bb[0], $bb[1]
// Bottom-Right: $bb[2], $bb[3]
// Top-Right: $bb[4]; $bb[5]
// Top-Left: $bb[6], $bb[7]
define('GDBB_TOP', 5);
define('GDBB_LEFT', 0);
define('GDBB_BOTTOM', 1);
define('GDBB_RIGHT', 2);

#[ In class constructor ]#
// Get size in pixels, must convert to points for GD2.
// Because GD2 assumes 96 pixels per inch and we use more "standard" 72.
$this->textSize *= 72/96;
$this->ComputeTextDimensions($this->textSize, FONT, $this->text);

#[ Remainder of the class (extract) ]
/**
 * Compute the dimensions of the text.
 */
function ComputeTextDimensions($textSize, $fontFile, $text)
{
    $this->textAreaWidth = $this->imageHSize - $this->marginL - $this->marginR;
    $this->textAreaHeight = $this->imageVSize - $this->marginT - $this->marginB;

    // Handle text on several lines
    $this->lines = explode(NEWLINE_CHAR, $text);
    $this->lineNb = count($this->lines);
    if ($this->lineNb == 1)
    {
        $bb = ImageTTFBBox($textSize, 0, $fontFile, $text);
        $this->textWidth[0] = $bb[GDBB_RIGHT] - $bb[GDBB_LEFT];
        $this->maxTextWidth = $this->textWidth[0];
        $this->textHeight[0] = $bb[GDBB_BOTTOM] - $bb[GDBB_TOP];
    }
    else
    {
        for ($i = 0; $i < $this->lineNb; $i++)
        {
            $bb = ImageTTFBBox($textSize, 0, $fontFile, $this->lines[$i]);
            $this->textWidth[$i] = $bb[GDBB_RIGHT] - $bb[GDBB_LEFT];
            $this->maxTextWidth = max($this->maxTextWidth, $this->textWidth[$i]);
            $this->textHeight[$i] = $bb[GDBB_BOTTOM] - $bb[GDBB_TOP];
        }
    }
    // Is the given text area width too small for asked text?
    if ($this->maxTextWidth > $this->textAreaWidth)
    {
        // Yes! Increase button size
        $this->textAreaWidth = $this->maxTextWidth;
        $this->imageHSize = $this->textAreaWidth + $this->marginL + $this->marginR;
    }
    // Now compute the text positions given the new (?) text area width
    if ($this->lineNb == 1)
    {
        $this->ComputeTextPosition(0, $textSize, $fontFile, $text, false);
    }
    else
    {
        for ($i = 0; $i < $this->lineNb; $i++)
        {
            $this->ComputeTextPosition($i, $textSize, $fontFile, $this->lines[$i], false);
        }
    }
}

/**
 * Compute xText and yText (text position) for the given text.
 */
function ComputeTextPosition($index, $textSize, $fontFile, $text, $centerAscDesc)
{
    switch ($this->textAlign)
    {
    case 'L':
        $this->xText[$index] = $this->marginL;
        break;
    case 'R':
        $this->xText[$index] = $this->marginL + 
                $this->textAreaWidth - $this->textWidth[$index];
        break;
    case 'C':
    default:
        $this->xText[$index] = $this->marginL + 
                ($this->textAreaWidth - $this->textWidth[$index]) / 2;
        break;
    }

    if ($centerAscDesc)
    {
        // Must compute the difference between baseline and bottom of BB.
        // I have to use a temporary image, as ImageTTFBBox doesn't use coordinates
        // providing offset from the baseline.
        $tmpBaseline = 5;
        // Image size isn't important here, GD2 still computes correct BB
        $tmpImage = ImageCreate(5, 5);
        $bbt = ImageTTFText($tmpImage, $this->textSize, 0, 0, $tmpBaseline,
                $this->color, $fontFile, $text);
        // Bottom to Baseline
        $baselinePos = $bbt[GDBB_BOTTOM] - $tmpBaseline;
        ImageDestroy($tmpImage);
        $this->yText[$index] = $this->marginT + $this->textAreaHeight -
                ($this->textAreaHeight - $this->textHeight) / 2 - $baselinePos + 0.5;
    }
    else
    {
        // Actually, we want to center the x-height, ie. to keep the baseline at same pos.
        // whatever the text is really, ie. independantly of ascenders and descenders.
        // This provide better looking buttons, as they are more consistent.
        $bbt = ImageTTFBBox($textSize, 0, $fontFile, "moxun");
        $tmpHeight = $bbt[GDBB_BOTTOM] - $bbt[GDBB_TOP];
        $this->yText[$index] = $this->marginT + $this->textAreaHeight -
                ($this->textAreaHeight - $tmpHeight) / 2 + 0.5;
    }
}

/**
 * Add the text to the button.
 */
function DrawText()
{
    for ($i = 0; $i < $this->lineNb; $i++)
    {
        // Increase slightly line height
        $yText = $this->yText[$i] + $this->textHeight[$i] * 1.1 * 
                ($i - ($this->lineNb - 1) / 2);
        ImageTTFText($this->image, $this->textSize, 0,
                $this->xText[$i], $yText, $this->color, FONT, $this->lines[$i]);
    }
}