php实现按指定大小等比缩放生成上传图片缩略图的方法

/**
 * *
 *等比缩放
 * @param unknown_type $srcImage   源图片路径
 * @param unknown_type $toFile     目标图片路径
 * @param unknown_type $maxWidth   最大宽
 * @param unknown_type $maxHeight  最大高
 * @param unknown_type $imgQuality 图片质量
 * @return unknown
 */
function resize($srcImage,$toFile,$maxWidth = 100,$maxHeight = 100,$imgQuality=100)
{
  
    list($width, $height, $type, $attr) = getimagesize($srcImage);
    if($width < $maxWidth  || $height < $maxHeight) return ;
    switch ($type) {
    case 1: $img = imagecreatefromgif($srcImage); break;
    case 2: $img = imagecreatefromjpeg($srcImage); break;
    case 3: $img = imagecreatefrompng($srcImage); break;
    }
    $scale = min($maxWidth/$width, $maxHeight/$height); //求出绽放比例
    
    if($scale < 1) {
    $newWidth = floor($scale*$width);
    $newHeight = floor($scale*$height);
    $newImg = imagecreatetruecolor($newWidth, $newHeight);
    imagecopyresampled($newImg, $img, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height);
    $newName = "";
    $toFile = preg_replace("/(.gif|.jpg|.jpeg|.png)/i","",$toFile);
 
    switch($type) {
        case 1: if(imagegif($newImg, "$toFile$newName.gif", $imgQuality))
        return "$newName.gif"; break;
        case 2: if(imagejpeg($newImg, "$toFile$newName.jpg", $imgQuality))
        return "$newName.jpg"; break;
        case 3: if(imagepng($newImg, "$toFile$newName.png", $imgQuality))
        return "$newName.png"; break;
        default: if(imagejpeg($newImg, "$toFile$newName.jpg", $imgQuality))
        return "$newName.jpg"; break;
    }
    imagedestroy($newImg);
    }
    imagedestroy($img);
    return false;
}