problème de redimensionnement d'image

bonjour,
je me permet de poster ce message car j'ai un petit souci concernant la mise en ligne de mon portfolio.
j'ai suivi le tuto de grafikart sur la réalisation d'un portfolio en 5 étapes. le projet à parfaitement marché en local mais lorsque je veux le mettre en ligne, le redimensionnement d'image ne se fait pas normalement. voici le message d'erreur que j'ai :

Warning: imagejpeg() [function.imagejpeg]: Unable to open 'home/stardeuc/dewy/www/img/works/96_150x150.jpg' for writing: No such file or directory in /home/stardeuc/dewy/www/lib/image.php on line 69

si vous voulez voici la librairie que j'utilise pour faire le redimensionnement d'image :

<?php
    function resizedname($file,$width,$height){
        $info = pathinfo($file);
        $return = '';

        if($info['dirname'] != '.'){
            $return .= $info['dirname'] . '/';
        }

        $return .= $info['filename'] . "_$width" . "x$height." . $info['extension'];
        return $return;
    }

    function resizeImage($file, $width, $height, $quality = 100){
        # We define the image dir include Theme support
        //$imageDir = (!isset($this->theme)) ? IMAGES : APP.'View'.DS.'Themed'.DS.$this->theme.DS.'webroot'.DS.'img'.DS;
        # We find the right file
        $pathinfo   = pathinfo(trim($file, '/'));
        //$file       = $imageDir . trim($file, '/');
        $output     = $pathinfo['dirname'] . '/' . $pathinfo['filename'] . '_' . $width . 'x' . $height . '.' . $pathinfo['extension'];

            # Setting defaults and meta
            $info                         = getimagesize($file);
            list($width_old, $height_old) = $info;
            # Create image ressource
            switch ( $info[2] ) {
                case IMAGETYPE_GIF:   $image = imagecreatefromgif($file);   break;
                case IMAGETYPE_JPEG:  $image = imagecreatefromjpeg($file);  break;
                case IMAGETYPE_PNG:   $image = imagecreatefrompng($file);   break;
                default: return false;
            }
            # We find the right ratio to resize the image before cropping
            $heightRatio = $height_old / $height;
            $widthRatio  = $width_old /  $width;
            $optimalRatio = $widthRatio;
            if ($heightRatio < $widthRatio) {
                $optimalRatio = $heightRatio;
            }
            $height_crop = ($height_old / $optimalRatio);
            $width_crop  = ($width_old  / $optimalRatio);
            # The two image ressources needed (image resized with the good aspect ratio, and the one with the exact good dimensions)
            $image_crop = imagecreatetruecolor( $width_crop, $height_crop );
            $image_resized = imagecreatetruecolor($width, $height);
            # This is the resizing/resampling/transparency-preserving magic
            if ( ($info[2] == IMAGETYPE_GIF) || ($info[2] == IMAGETYPE_PNG) ) {
                $transparency = imagecolortransparent($image);
                if ($transparency >= 0) {
                    $transparent_color  = imagecolorsforindex($image, $trnprt_indx);
                    $transparency       = imagecolorallocate($image_crop, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);
                    imagefill($image_crop, 0, 0, $transparency);
                    imagecolortransparent($image_crop, $transparency);
                    imagefill($image_resized, 0, 0, $transparency);
                    imagecolortransparent($image_resized, $transparency);
                }elseif ($info[2] == IMAGETYPE_PNG) {
                    imagealphablending($image_crop, false);
                    imagealphablending($image_resized, false);
                    $color = imagecolorallocatealpha($image_crop, 0, 0, 0, 127);
                    imagefill($image_crop, 0, 0, $color);
                    imagesavealpha($image_crop, true);
                    imagefill($image_resized, 0, 0, $color);
                    imagesavealpha($image_resized, true);
                }
            }
            imagecopyresampled($image_crop, $image, 0, 0, 0, 0, $width_crop, $height_crop, $width_old, $height_old);
            imagecopyresampled($image_resized, $image_crop, 0, 0, ($width_crop - $width) / 2, ($height_crop - $height) / 2, $width, $height, $width, $height);
            # Writing image according to type to the output destination and image quality
            switch ( $info[2] ) {
              case IMAGETYPE_GIF:   imagegif($image_resized, $output, 80);    break;
              case IMAGETYPE_JPEG:  imagejpeg($image_resized, $output, 80);   break;
              case IMAGETYPE_PNG:   imagepng($image_resized, $output, 9);    break;
              default: return false;
            }

        return true;  

    }

j'ai déjà posté un commentaire sur les commentaires du tuto du portfolio numéro 5. je n'avais pas vu le forum.
est ce quelqu'un à une idée?
merci d'avance