Magento: Image Resize functionality

1. Add the following function in your Helper file

public function resizeImage($imageName, $width=NULL, $height=NULL, $imagePath=NULL) {
        
    $imagePath = str_replace("/", DS, $imagePath);
    $imagePathFull = Mage::getBaseDir('media') . DS . $imagePath . DS . $imageName;
    if($width == NULL && $height == NULL) {
    $width = 450;
    $height = 450;
    }
    $resizePath = $width . 'x' . $height;
    $resizePathFull = Mage::getBaseDir('media') . DS . $imagePath . DS . $resizePath . DS . $imageName;
    if (file_exists($imagePathFull) && !file_exists($resizePathFull)) {
    $imageObj = new Varien_Image($imagePathFull);
    $imageObj->constrainOnly(TRUE);
    $imageObj->keepAspectRatio(TRUE);
    $imageObj->resize($width,$height);
    $imageObj->save($resizePathFull);
    }
    $imagePath=str_replace(DS, "/", $imagePath);
    return Mage::getBaseUrl("media") . $imagePath . "" . $resizePath . "/" . $imageName;
}

2. In your template file call image src :

Mage::helper('yourmodule')->resizeImage('imagename', 545, 160, 'imagepath')