Image Preview functionality in SharePoint

Question:
How to display the Image preview without actually uploading the file in SharePoint?

Solution:
To check the image preview we can temporary move/place the file in Layout folder. Then pass URL in following format to Image control:
"/_layouts/images/MYFOLDER/MyImageName.jpg

After checking the Image preview and final upload of image file, we can delete the temporary image file from 12 hive.

Code snippet (comments are self-explanatory):

FileUpload FileUploadImage; //FileUpload control to select image file
Image myImage; //Image control to be used for preview functionality

//Getting 12 hive path through SPUtility.GetGenericSetupPath() function
string folderPath = 
Microsoft.SharePoint.Utilities.SPUtility.GetGenericSetupPath("TEMPLATE") 
+ "\\IMAGES\\MYFOLDER\\";

//Check folder path
if (!Directory.Exists(folderPath))
   Directory.CreateDirectory(folderPath);

//Copy the image file to a temporary folder in 12 hive
File.WriteAllBytes(folderPath + FileUploadImage.FileName,
          FileUploadImage.FileBytes);

/* //File.Copy() will not work in case of remote image upload
File.Copy(FileUploadImage.PostedFile.FileName, 
          folderPath + FileUploadImage.FileName, true);
*/

//Set the URL of image control
myImage.ImageUrl = 
       "/_layouts/images/MYFOLDER/" + FileUploadImage.FileName;

Note: In a similar manner we can preview media file (like *.wmv) before actual upload in SharePoint.