<?php
$imagefolder='.';
$thumbsfolder='.';
$pics=directory($imagefolder,"jpg,JPG,JPEG,jpeg,png,PNG");
$pics=ditchtn($pics,"tn_");
if ($pics[0]!="")
{
    foreach ($pics as $p)
    {
        createthumb($p,"tn_".$p,150,150);
    }
}

/*
    Function ditchtn($arr,$thumbname)
    filters out thumbnails
*/
function ditchtn($arr,$thumbname)
{
    foreach ($arr as $item)
    {
        if (!preg_match("/^".$thumbname."/",$item)){$tmparr[]=$item;}
    }
    return $tmparr;
}

/*
    Function createthumb($name,$filename,$new_w,$new_h)
    creates a resized image
    variables:
    $name        Original filename
    $filename    Filename of the resized image
    $new_w        width of resized image
    $new_h        height of resized image
*/    
function createthumb($name,$filename,$new_w,$new_h)
{
    $system=explode(".",$name);
    if (preg_match("/jpg|jpeg/",$system[1])){$src_img=imagecreatefromjpeg($name);}
    if (preg_match("/png/",$system[1])){$src_img=imagecreatefrompng($name);}
    $old_x=imageSX($src_img);
    $old_y=imageSY($src_img);
    if ($old_x > $old_y)
    {
        $thumb_w=$new_w;
        $thumb_h=$old_y*($new_h/$old_x);
    }
    if ($old_x < $old_y)
    {
        $thumb_w=$old_x*($new_w/$old_y);
        $thumb_h=$new_h;
    }
    if ($old_x == $old_y)
    {
        $thumb_w=$new_w;
        $thumb_h=$new_h;
    }
    $dst_img=ImageCreateTrueColor($thumb_w,$thumb_h);
    imagecopyresampled($dst_img,$src_img,0,0,0,0,$thumb_w,$thumb_h,$old_x,$old_y);
    if (preg_match("/png/",$system[1]))
    {
        imagepng($dst_img,$filename);
    } else {
        imagejpeg($dst_img,$filename);
    }
    imagedestroy($dst_img);
    imagedestroy($src_img);
}

/*
        Function directory($directory,$filters)
        reads the content of $directory, takes the files that apply to $filter
        and returns an array of the filenames.
        You can specify which files to read, for example
        $files = directory(".","jpg,gif");
                gets all jpg and gif files in this directory.
        $files = directory(".","all");
                gets all files.
*/
function directory($dir,$filters)
{
    $handle=opendir($dir);
    $files=array();
    if ($filters == "all"){while(($file = readdir($handle))!==false){$files[] = $file;}}
    if ($filters != "all")
    {
        $filters=explode(",",$filters);
        while (($file = readdir($handle))!==false)
        {
            for ($f=0;$f<sizeof($filters);$f++):
                $system=explode(".",$file);
                if ($system[1] == $filters[$f]){$files[] = $file;}
            endfor;
        }
    }
    closedir($handle);
    return $files;
}
?>

ได้โค๊ดมาแต่ประยุกต์ใช้ไม่เป็นครับ ต้องการให้สร้าง thumbnail เก็บไว้อีกโฟลเดอร์นึงด้วย ในขณะทีเราอัพรูปขึ้นไปครับ รบกวนด้วยครับ

ปล.ถ้าท่านเอดมินมีสคริปอื่นแนะนำก็ได้ครับ ขอบคุณครับ

ได้แล้วครับ โทษทีครับ

<?php
//define a maxim size for the uploaded images
define ("MAX_SIZE","100");
// define the width and height for the thumbnail
// note that theese dimmensions are considered the maximum dimmension and are not fixed,
// because we have to keep the image ratio intact or it will be deformed
define ("WIDTH","150");
define ("HEIGHT","100");

// this is the function that will create the thumbnail image from the uploaded image
// the resize will be done considering the width and height defined, but without deforming the image
function make_thumb($img_name,$filename,$new_w,$new_h)
{
//get image extension.
$ext=getExtension($img_name);
//creates the new image using the appropriate function from gd library
if(!strcmp("jpg",$ext) || !strcmp("jpeg",$ext))
$src_img=imagecreatefromjpeg($img_name);

if(!strcmp("png",$ext))
$src_img=imagecreatefrompng($img_name);

//gets the dimmensions of the image
$old_x=imageSX($src_img);
$old_y=imageSY($src_img);

// next we will calculate the new dimmensions for the thumbnail image
// the next steps will be taken:
// 1. calculate the ratio by dividing the old dimmensions with the new ones
// 2. if the ratio for the width is higher, the width will remain the one define in WIDTH variable
// and the height will be calculated so the image ratio will not change
// 3. otherwise we will use the height ratio for the image
// as a result, only one of the dimmensions will be from the fixed ones
$ratio1=$old_x/$new_w;
$ratio2=$old_y/$new_h;
if($ratio1>$ratio2) {
$thumb_w=$new_w;
$thumb_h=$old_y/$ratio1;
}
else {
$thumb_h=$new_h;
$thumb_w=$old_x/$ratio2;
}

// we create a new image with the new dimmensions
$dst_img=ImageCreateTrueColor($thumb_w,$thumb_h);

// resize the big image to the new created one
imagecopyresampled($dst_img,$src_img,0,0,0,0,$thumb_w,$thumb_h,$old_x,$old_y);

// output the created image to the file. Now we will have the thumbnail into the file named by $filename
if(!strcmp("png",$ext))
imagepng($dst_img,$filename);
else
imagejpeg($dst_img,$filename);

//destroys source and destination images.
imagedestroy($dst_img);
imagedestroy($src_img);
}

// This function reads the extension of the file.
// It is used to determine if the file is an image by checking the extension.
function getExtension($str) {
$i = strrpos($str,".");
if (!$i) { return ""; }
$l = strlen($str) - $i;
$ext = substr($str,$i+1,$l);
return $ext;
}

// This variable is used as a flag. The value is initialized with 0 (meaning no error found)
//and it will be changed to 1 if an errro occures. If the error occures the file will not be uploaded.
$errors=0;
// checks if the form has been submitted
if(isset($_POST['Submit']))
{
//reads the name of the file the user submitted for uploading
$image=$_FILES['image']['name'];
// if it is not empty
if ($image)
{
// get the original name of the file from the clients machine
$filename = stripslashes($_FILES['image']['name']);

// get the extension of the file in a lower case format
$extension = getExtension($filename);
$extension = strtolower($extension);
// if it is not a known extension, we will suppose it is an error, print an error message
//and will not upload the file, otherwise we continue
if (($extension != "jpg") && ($extension != "jpeg") && ($extension != "png"))
{
echo '<h1>Unknown extension!</h1>';
$errors=1;
}
else
{
// get the size of the image in bytes
// $_FILES[\'image\'][\'tmp_name\'] is the temporary filename of the file in which the uploaded file was stored on the server
$size=getimagesize($_FILES['image']['tmp_name']);
$sizekb=filesize($_FILES['image']['tmp_name']);

//compare the size with the maxim size we defined and print error if bigger
if ($sizekb > MAX_SIZE*1024)
{
echo '<h1>You have exceeded the size limit!</h1>';
$errors=1;
}

//we will give an unique name, for example the time in unix time format
$image_name=time().'.'.$extension;
//the new name will be containing the full path where will be stored (images folder)
$newname="images/".$image_name;
$copied = copy($_FILES['image']['tmp_name'], $newname);
//we verify if the image has been uploaded, and print error instead
if (!$copied)
{
echo '<h1>Copy unsuccessfull!</h1>';
$errors=1;
}
else
{
// the new thumbnail image will be placed in images/thumbs/ folder
$thumb_name='images/thumbs/thumb_'.$image_name;
// call the function that will create the thumbnail. The function will get as parameters
//the image name, the thumbnail name and the width and height desired for the thumbnail
$thumb=make_thumb($newname,$thumb_name,WIDTH,HEIGHT);
}} }}

//If no errors registred, print the success message and show the thumbnail image created
if(isset($_POST['Submit']) && !$errors)
{
echo "<h1>Thumbnail created Successfully!</h1>";
echo '<img src="'.$thumb_name.'">';
}

?>
<!-- next comes the form, you must set the enctype to "multipart/form-data" and use an input type "file" -->

<form name="newad" method="post" enctype="multipart/form-data" action="">
<table>
<tr><td><input type="file" name="image" ></td></tr>
<tr><td><input name="Submit" type="submit" value="Upload image"></td></tr>
</table>
</form>

เผื่อใครเอาสคริปไปใช้...

1. ให้สร้างโฟลเดอร์ชื่อ images
2. สร้าง sub folder ชื่อ thumbs ไว้ในโฟลเดอร์ images อีกที

เท่านี้ก็ใช้ได้แระ โดยที่ไฟล์ขนาดปกติจะถูกเก็บในโฟลเดอร์ images ส่วนไฟล์ thumbnail จะถูกเก็บใน sub folder ชื่อ thumbs ครับ 

ตามโค๊ดนี้เป็นการ สร้าง thumbnails จากรูปภาพที่มีอยู่ในระบบแล้วครับ
ซึ่งถ้าต้องการให้สร้าง thumbnails จากรูปภาพที่ทำการ upload โดยอัตโนมัติผมว่าทำการ resize on the fly เลยดีกว่าครับ

ผมจำไม่ได้เอา source ไปไว้ไหนลองอ่านที่นี่ดูนะครับ
http://www.weberdev.com/get_example-3938.html
http://www.finalwebsites.com/snippets.php?id=7
http://www.web-lab.co.yu/php.php
http://www.phpbuilder.com/board/archive/index.php/t-10240409.html

ได้แล้วครับ ขอบคุณมากครับผม