PHP+Ajax图片上传并且无刷新生成缩略图预览

 <div id="upload-wrapper">  <div align="center">    <form action="processupload.php" method="post" enctype="multipart/form-data" id="MyUploadForm">  <input name="ImageFile" id="imageInput" type="file" />  <input type="submit"  id="submit-btn" value="Upload" />  <img src="images/ajax-loader.gif" id="loading-img"   style="max-width:90%" alt="Please Wait"/>  </form>  <div id="output"></div>  </div>  
</div>

<script type="text/javascript">  
$(document).ready(function() {   
    var options = {   
            target:   '#output',   // target element(s) to be updated with server response   
            beforeSubmit:  beforeSubmit,  // pre-submit callback   
            success:       afterSuccess,  // post-submit callback   
            resetForm: true        // reset the form after successful submit   
        };   
          
     $('#MyUploadForm').submit(function() {   
            $(this).ajaxSubmit(options);              
            // always return false to prevent standard browser submit and page navigation   
            return false;   
        });   
});   
  
function afterSuccess()  
{  
    $('#submit-btn').show(); //hide submit button  
    $('#loading-img').hide(); //hide submit button  
  
}  
  
//function to check file size before uploading.  
function beforeSubmit(){  
    //check whether browser fully supports all File API  
   if (window.File && window.FileReader && window.FileList && window.Blob)  
    {  
          
        if( !$('#imageInput').val()) //check empty input filed  
        {  
            $("#output").html("Are you kidding me?");  
            return false  
        }  
          
        var fsize = $('#imageInput')[0].files[0].size; //get file size  
        var ftype = $('#imageInput')[0].files[0].type; // get file type  
          
  
        //allow only valid image file types   
        switch(ftype)  
        {  
            case 'image/png': case 'image/gif': case 'image/jpeg': case 'image/pjpeg':  
                break;  
            default:  
                $("#output").html("<b>"+ftype+"</b> Unsupported file type!");  
                return false  
        }  
          
        //Allowed file size is less than 1 MB (1048576)  
        if(fsize>1048576)   
        {  
            $("#output").html("<b>"+bytesToSize(fsize) +"</b> Too big Image file! <br />Please reduce the size of your photo using an image editor.");  
            return false  
        }  
                  
        $('#submit-btn').hide(); //hide submit button  
        $('#loading-img').show(); //hide submit button  
        $("#output").html("");    
    }  
    else  
    {  
        //Output error to older unsupported browsers that doesn't support HTML5 File API  
        $("#output").html("Please upgrade your browser, because your current browser lacks some new features we need!");  
        return false;  
    }  
}  
  
//function to format bites bit.ly/19yoIPO  
function bytesToSize(bytes) {  
   var sizes = ['Bytes', 'KB', 'MB', 'GB', 'TB']; 
   if (bytes == 0) return '0 Bytes'; 
   var i = parseInt(Math.floor(Math.log(bytes) / Math.log(1024))); 
   return Math.round(bytes / Math.pow(1024, i), 2) + ' ' + sizes[i];  
}  
  
</script>

<?php  
if(isset($_POST))  
{  
    ############ Edit settings ##############  
    $ThumbSquareSize        = 200; //Thumbnail will be 200x200  
    $BigImageMaxSize        = 500; //Image Maximum height or width  
    $ThumbPrefix            = "thumb_"; //Normal thumb Prefix  
    $DestinationDirectory   = '../upload/'; //specify upload directory ends with / (slash)  
    $Quality                = 90; //jpeg quality  
    ##########################################  
      
    //check if this is an ajax request  
    if (!isset($_SERVER['HTTP_X_REQUESTED_WITH'])){  
        die();  
    }  
      
    // check $_FILES['ImageFile'] not empty  
    if(!isset($_FILES['ImageFile']) || !is_uploaded_file($_FILES['ImageFile']['tmp_name']))  
    {  
            die('Something wrong with uploaded file, something missing!'); // output error when above checks fail.  
    }  
      
    // Random number will be added after image name  
    $RandomNumber   = rand(0, 9999999999);   
  
    $ImageName      = str_replace(' ','-',strtolower($_FILES['ImageFile']['name'])); //get image name  
    $ImageSize      = $_FILES['ImageFile']['size']; // get original image size  
    $TempSrc        = $_FILES['ImageFile']['tmp_name']; // Temp name of image file stored in PHP tmp folder  
    $ImageType      = $_FILES['ImageFile']['type']; //get file type, returns "image/png", image/jpeg, text/plain etc.  
  
    //Let's check allowed $ImageType, we use PHP SWITCH statement here  
    switch(strtolower($ImageType))  
    {  
        case 'image/png': 
            //Create a new image from file  
            $CreatedImage =  imagecreatefrompng($_FILES['ImageFile']['tmp_name']); 
            break; 
        case 'image/gif': 
            $CreatedImage =  imagecreatefromgif($_FILES['ImageFile']['tmp_name']); 
            break;           
        case 'image/jpeg': 
        case 'image/pjpeg': 
            $CreatedImage = imagecreatefromjpeg($_FILES['ImageFile']['tmp_name']); 
            break; 
        default: 
            die('Unsupported File!'); //output error and exit 
    } 
     
    //PHP getimagesize() function returns height/width from image file stored in PHP tmp folder. 
    //Get first two values from image, width and height.  
    //list assign svalues to $CurWidth,$CurHeight 
    list($CurWidth,$CurHeight)=getimagesize($TempSrc); 
     
    //Get file extension from Image name, this will be added after random name 
    $ImageExt = substr($ImageName, strrpos($ImageName, '.')); 
    $ImageExt = str_replace('.','',$ImageExt); 
     
    //remove extension from filename 
    $ImageName      = preg_replace("/\.[^.\s]{3,4}$/", "", $ImageName);  
     
    //Construct a new name with random number and extension. 
    $NewImageName = $ImageName.'-'.$RandomNumber.'.'.$ImageExt; 
     
    //set the Destination Image 
    $thumb_DestRandImageName    = $DestinationDirectory.$ThumbPrefix.$NewImageName; //Thumbnail name with destination directory 
    $DestRandImageName          = $DestinationDirectory.$NewImageName; // Image with destination directory 
     
    //Resize image to Specified Size by calling resizeImage function. 
    if(resizeImage($CurWidth,$CurHeight,$BigImageMaxSize,$DestRandImageName,$CreatedImage,$Quality,$ImageType)) 
    { 
        //Create a square Thumbnail right after, this time we are using cropImage() function 
        if(!cropImage($CurWidth,$CurHeight,$ThumbSquareSize,$thumb_DestRandImageName,$CreatedImage,$Quality,$ImageType)) 
            { 
                echo 'Error Creating thumbnail'; 
            } 
        /* 
        We have succesfully resized and created thumbnail image 
        We can now output image to user's browser or store information in the database  
        */  
        echo '<table width="100%" border="0" cellpadding="4" cellspacing="0">';  
        echo '<tr>';  
        echo '<td align="center"><img src="../upload/'.$ThumbPrefix.$NewImageName.'" alt="Thumbnail"></td>';  
        echo '</tr><tr>';  
        echo '<td align="center"><img src="../upload/'.$NewImageName.'" alt="Resized Image"></td>';  
        echo '</tr>';  
        echo '</table>';  
  
        /* 
        // Insert info into database table! 
        mysql_query("INSERT INTO myImageTable (ImageName, ThumbName, ImgPath) 
        VALUES ($DestRandImageName, $thumb_DestRandImageName, 'uploads/')"); 
        */  
  
    }else{  
        die('Resize Error'); //output error  
    }  
}  
  
  
// This function will proportionally resize image   
function resizeImage($CurWidth,$CurHeight,$MaxSize,$DestFolder,$SrcImage,$Quality,$ImageType)  
{  
    //Check Image size is not 0  
    if($CurWidth <= 0 || $CurHeight <= 0)   
    {  
        return false;  
    }  
      
    //Construct a proportional size of new image  
    $ImageScale         = min($MaxSize/$CurWidth, $MaxSize/$CurHeight);   
    $NewWidth           = ceil($ImageScale*$CurWidth);  
    $NewHeight          = ceil($ImageScale*$CurHeight);  
    $NewCanves          = imagecreatetruecolor($NewWidth, $NewHeight);  
      
    // Resize Image  
    if(imagecopyresampled($NewCanves, $SrcImage,0, 0, 0, 0, $NewWidth, $NewHeight, $CurWidth, $CurHeight))  
    {  
        switch(strtolower($ImageType))  
        {  
            case 'image/png':  
                imagepng($NewCanves,$DestFolder);  
                break;  
            case 'image/gif':  
                imagegif($NewCanves,$DestFolder);  
                break;            
            case 'image/jpeg':  
            case 'image/pjpeg':  
                imagejpeg($NewCanves,$DestFolder,$Quality);  
                break;  
            default:  
                return false;  
        }  
    //Destroy image, frees memory     
    if(is_resource($NewCanves)) {imagedestroy($NewCanves);}   
    return true;  
    }  
  
}  
  
//This function corps image to create exact square images, no matter what its original size!  
function cropImage($CurWidth,$CurHeight,$iSize,$DestFolder,$SrcImage,$Quality,$ImageType)  
{      
    //Check Image size is not 0  
    if($CurWidth <= 0 || $CurHeight <= 0)   
    {  
        return false;  
    }  
      
    //abeautifulsite.net has excellent article about "Cropping an Image to Make Square bit.ly/1gTwXW9  
    if($CurWidth>$CurHeight)  
    {  
        $y_offset = 0;  
        $x_offset = ($CurWidth - $CurHeight) / 2;  
        $square_size    = $CurWidth - ($x_offset * 2);  
    }else{  
        $x_offset = 0;  
        $y_offset = ($CurHeight - $CurWidth) / 2;  
        $square_size = $CurHeight - ($y_offset * 2);  
    }  
      
    $NewCanves  = imagecreatetruecolor($iSize, $iSize);   
    if(imagecopyresampled($NewCanves, $SrcImage,0, 0, $x_offset, $y_offset, $iSize, $iSize, $square_size, $square_size))  
    {  
        switch(strtolower($ImageType))  
        {  
            case 'image/png':  
                imagepng($NewCanves,$DestFolder);  
                break;  
            case 'image/gif':  
                imagegif($NewCanves,$DestFolder);  
                break;            
            case 'image/jpeg':  
            case 'image/pjpeg':  
                imagejpeg($NewCanves,$DestFolder,$Quality);  
                break;  
            default:  
                return false;  
        }  
    //Destroy image, frees memory     
    if(is_resource($NewCanves)) {imagedestroy($NewCanves);}   
    return true;  
  
    }  
        
}