timeout vid skapande av tumnaglar

jag använder följande skript för generering av tumnaglar:

<?

// scalePic(infil, utfil, max X-storlek, max Y-storlek, kvalitet (0-100));

function scalePic($filnamn, $nyttfilnamn, $maxX, $maxY, $kvalitet = 75) {
    $im = ImageCreateFromJPEG($filnamn);
    
	
    $im_width=imageSX($im);
    $im_height=imageSY($im);
    
    if ($maxX > $maxY) {
        $factor = $maxX/$im_width;
        $new_width = $maxX;
        $new_height = $im_height * $factor;
        }
    else {
        $factor = $maxY/$im_width;
        $new_width = $maxY;
        $new_height = $im_height * $factor;
        }
    
    // resize
    $new_im=imagecreatetruecolor($new_width,$new_height);
     ImageCopyResampleBicubic($new_im,$im,0,0,0,0,$new_width,$new_height,$im_width,$im_height);

    // output
    Imagejpeg($new_im,$nyttfilnamn,$kvalitet); // quality 75
        
    // cleanup
    ImageDestroy($im);
    ImageDestroy($new_im);
    }

    
function ImageCopyResampleBicubic ($dst_img, $src_img, $dst_x, $dst_y, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h)
/*
port to PHP by John Jensen July 10 2001 -- original code (in C, for the PHP
GD Module) by [email]jernberg@fairytale.se[/email]
*/
{
    for ($i = 0; $i < 256; $i++) {  // get pallete. Is this algoritm correct?
        $colors = ImageColorsForIndex ($src_img, $i);
        ImageColorAllocate ($dst_img, $colors['red'], $colors['green'], $colors['blue']);
    }

    $scaleX = ($src_w - 1) / $dst_w;
    $scaleY = ($src_h - 1) / $dst_h;

    $scaleX2 = $scaleX / 2.0;
    $scaleY2 = $scaleY / 2.0;

    for ($j = $src_y; $j < $dst_h; $j++) {
        $sY = $j * $scaleY;

        for ($i = $src_x; $i < $dst_w; $i++) {
            $sX = $i * $scaleX;

            $c1 = ImageColorsForIndex ($src_img, ImageColorAt ($src_img, (int) $sX, (int) $sY + $scaleY2));
            $c2 = ImageColorsForIndex ($src_img, ImageColorAt ($src_img, (int) $sX, (int) $sY));
            $c3 = ImageColorsForIndex ($src_img, ImageColorAt ($src_img, (int) $sX + $scaleX2, (int) $sY + $scaleY2));
            $c4 = ImageColorsForIndex ($src_img, ImageColorAt ($src_img, (int) $sX + $scaleX2, (int) $sY));

            $red = (int) (($c1['red'] + $c2['red'] + $c3['red'] + $c4['red']) / 4);
            $green = (int) (($c1['green'] + $c2['green'] + $c3['green'] + $c4['green']) / 4);
            $blue = (int) (($c1['blue'] + $c2['blue'] + $c3['blue'] + $c4['blue']) / 4);

            $color = ImageColorClosest ($dst_img, $red, $green, $blue); 
            ImageSetPixel ($dst_img, $i + $dst_x, $j + $dst_y, $color); 
        }
    }
}

?>

När jag anropar skriptet får jag följande fel:

Fatal error: Maximum execution time of 30 seconds exceeded in /home/ServerRoots/www/album/gd_source.php on line 60

Raderna kring 60:

            $c1 = ImageColorsForIndex ($src_img, ImageColorAt ($src_img, (int) $sX, (int) $sY + $scaleY2));
            $c2 = ImageColorsForIndex ($src_img, ImageColorAt ($src_img, (int) $sX, (int) $sY));
            $c3 = ImageColorsForIndex ($src_img, ImageColorAt ($src_img, (int) $sX + $scaleX2, (int) $sY + $scaleY2));
            $c4 = ImageColorsForIndex ($src_img, ImageColorAt ($src_img, (int) $sX + $scaleX2, (int) $sY));

vad beror det på? finns nåt sätt att få fram ngn debugginginfo? ImageColorsForIndex() samt ImageColorAt() har jag provat var för sig utan att kunna reproducera felet.

/r
under tiden jag kör php-filen tar apache drygt 90 % av cpu:n. någonting är ju märkligt här! :)