This one is a port of the Imagetext plugin for Smarty. So as I won't include the credit in this snippet please check them in the Smarty plugin itself here.

Requirements

In order to make it work, this is what you need : - A 'fonts' folder in your projects' data directory, in which you copy the .ttf files you need - The following helper :

function imagetext($text,$styleName=null,$params=array())
    {
        if(!$styleName){
            $styleName='default';
        }
        if (empty($text)) { return; }
        // Which style is in use
        $style=sfConfig::get('app_imagetext_styles');
        $style=$style[$styleName];
        // Param values overwrite style values
        foreach ($params as $key=>$value) $style[$key] = $value;
        // Error handling
        if (empty($style['font'])) { throw new sfViewException("imagetext: missing 'font' parameter"); return; }
        if (empty($style['size'])) { throw new sfViewException("imagetext: missing 'size' parameter"); return; }
        if (empty($style['bgcolor'])) { $style['bgcolor'] = 'FFFFFF'; }
        if (empty($style['fgcolor'])) { $style['fgcolor'] = '000000';  }
 
    ### Preferences
    $cacheDir=sfConfig::get('sf_web_dir').DIRECTORY_SEPARATOR.'images'.DIRECTORY_SEPARATOR.'imagetext'.DIRECTORY_SEPARATOR;
    $cacheUrl='imagetext/';
    $fontDir=sfConfig::get('sf_data_dir').DIRECTORY_SEPARATOR.'fonts'.DIRECTORY_SEPARATOR;  
    $text = preg_replace("=<br( /)?>=i", "\n", $text);
 
    // Which font is in use
    $font = $fontDir.$style['font'];
    // Hash of text and all parameters for the cache function
    $hash = md5(implode('',$style).$text);
    // The url of the created image
    $imgFile    = $cacheDir.$styleName.'_'.$hash.'.'.$style['format'];
    $imgUrl = $cacheUrl.$styleName.'_'.$hash.'.'.$style['format'];
 
    ### Use cached image if available
    if (file_exists($imgFile) && @$style['dev'] != true && @$style['dynamic'] != true) 
          if (@$style['urlonly'] == 'true') return $imgUrl; else
        return @$style['prehtml'].image_tag($imgUrl,array('style'=>'border: 0 px solid #00ff00','alt'=>preg_replace("=\r\n|\r|\n|\t=", ' ', htmlspecialchars($text)))).@$style['posthtml'];
 
    ### otherwise create it
    // Function to get a color handler of hex values
    if (!function_exists('fromhex'))
        {
        function fromhex($image,$string) {
            sscanf($string, "%2x%2x%2x", $red, $green, $blue);
            return ImageColorAllocate($image,$red,$green,$blue);
            }
        }
 
    ### create a four times larger image to improve kerning
    // The multiplier. The bigger the better the kerning and the typeface, but the slower the creation
    $multi = 4;
 
    // If "pixelfont" don´t use multiplier
    if ($style['pixelfont'] == 1) $multi = 1;
 
    // Calculate measures of image
    $bbox = imagettfbbox ($style['size']*$multi, 0, $font, $text);
    $xcorr = 0-$bbox[6]; // northwest X
    $ycorr = 0-$bbox[7]; // northwest Y
    $box['left']    = $bbox[6]+$xcorr+$style['x']*$multi;
    $box['height']  = abs($bbox[5])+abs($bbox[1]);
    $box['width']   = abs($bbox[2])+abs($bbox[0])+$style['x']*$multi;
    $box['top']     = abs($bbox[5]);
 
    // Create the big image
    $im = imagecreate ($box['width'], $box['height']);
    $bgcolor = fromhex($im,$style['bgcolor']);
    $fgcolor = fromhex($im,$style['fgcolor']);
    if ($style['pixelfont'] == 1) $fgcolor = -$fgcolor;
    imagettftext ($im, $style['size']*$multi, 0, $box['left'], $box['top'], $fgcolor, $font, $text);
 
    // Sample down the big image
    $width = $style['width']+$style['addx'];
    $height = $style['height']+$style['addy'];
 
    // Overwrite when height oder width is given
    if (empty($style['width'])) $width = $box['width']/$multi+$style['addx']+$style['x'];
    if (empty($style['height'])) $height = $box['height']/$multi+$style['addy']+$style['y'];
 
    $ds = imagecreatetruecolor ($width, $height);
    $bgcolor2 = fromhex($ds,$style['bgcolor']);
    imageFill($ds,0,0,$bgcolor2);
    imagecopyresampled($ds,$im,0,$style['y'],0,0,$box['width']/$multi, $box['height']/$multi,$box['width'], $box['height']);
    imagetruecolortopalette($ds,0,256);
    imagepalettecopy($ds,$im);
    ImageColorTransparent($ds,$bgcolor);
 
 
    // write whereto?
    if ($style['format'] == 'gif') ImageGIF ($ds,$imgFile); else ImagePNG ($ds,$imgFile);
    ImageDestroy ($im);
    ImageDestroy ($ds);
 
    // and display
    if ($style['dev']) $border = 1; else $border = 0;
  if ($style['urlonly'] == 'true') return $imgUrl;
        else
    return $style['prehtml'].image_tag($imgUrl,array('style'=>'border: '.$border.'px solid #00ff00','alt'=>preg_replace("=\r\n|\r|\n|\t=", ' ', htmlspecialchars($text)))).$style['posthtml'];
}

As you can see in this code styles can (at least 'default' MUST be) be configured in app.yml. This is an example style config :

    imagetext:
        styles:
            default:
                font:   hockey.ttf
                size:   18
                format: png

So now you can use the helper in your templates :

<?php use_helper('imageText') ?>
 
<? echo imagetext('This is my title') ?>
<p>Some blah blah</p>
<? echo imagetext('This is another headline style','anotherstyle') ?>

This helper uses GD so depending on which version you have installed, you might or might not handle PNG or GIF.