Magento Resize Any Image

Please put following function in helper file of your module.

public function resizeImg($fileName, $width, $height = '')
{
    $folderURL = Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_MEDIA);
    $imageURL = $folderURL . $fileName;

    $basePath = Mage::getBaseDir(Mage_Core_Model_Store::URL_TYPE_MEDIA) . DS . $fileName;
    $newPath = Mage::getBaseDir(Mage_Core_Model_Store::URL_TYPE_MEDIA) . DS . "resized" . DS . $fileName;
    //if width empty then return original size image's URL
    if ($width != '') {
        //if image has already resized then just return URL
        if (file_exists($basePath) && is_file($basePath) && !file_exists($newPath)) {
            $imageObj = new Varien_Image($basePath);
            $imageObj->constrainOnly(TRUE);
            $imageObj->keepAspectRatio(FALSE);
            $imageObj->keepFrame(FALSE);
            $imageObj->resize($width, $height);
            $imageObj->save($newPath);
        }
        $resizedURL = Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_MEDIA) . "resized" . DS . $fileName;
     } else {
        $resizedURL = $imageURL;
     }
     return $resizedURL;
}

you can call this function

<?php Mage::helper('modulename')->resizeImg($item->getThumbnail(),100,100); ?>