参数无效在C＃中创建新的位图时发生异常？

Question

We have a method to save an image as corrected format as the following :

public static string SaveImageAsCorrectFormat(string tempFilePath, string newFileName, string destinationDirectoryPath)
{
    using (Image image = new Bitmap(tempFilePath))// Exception : Parameter is not valid.
    {
        string extension = image.RawFormat.GetExtension();
        string newAbsoluteFilePath = Path.Combine(destinationDirectoryPath, string.Format("{0}.{1}", newFileName, extension));
        image.Save(newAbsoluteFilePath, image.RawFormat);
        return newAbsoluteFilePath;
    }
}

but in in the following line an exception has occurred :

//Parameter is not valid.
using (Image image = new Bitmap(tempFilePath))

I changed it to the following but Out of memory has occurred :

 // Out of memory
using (Bitmap image = (Bitmap)Image.FromFile(tempFilePath))

The image size is 10KB and 10GB of RAM is free.

What's the problem?

PS:
I don't have the problem in local. But when I publish the software on server this problem occur.

Edit:
I'm using windows Server 2012 R2 and IIS 8.5.9600.16384 . The Application (website) has full control on IIS_IUSRS and IUSR .
I think the problem isn't related to permission, because I could open the file with the following code :

using (FileStream fileStream = File.Open(tempFilePath, FileMode.Open)) // OK
using (Image image = new Bitmap(fileStream))// Exception : Parameter is not valid.

Solution:
I changed website application pool identity to Local System and it's OK now, Is it OK to change application pool identity or it is a security hole ?

Answer 1

It appears that the image is corrupted, or maybe just has the wrong file extension.

If the extension is jpeg , .NET will attempt to decode it as a JPEG. Note that this behaviour differs from browsers: browsers tend to look at the content of the file and decide its format based on that; due to this, you could be under the misconception that a jpeg file is fine because it displays in the browser, when in reality it contains a PNG image.

If you open the image file in Firefox, the window titlebar tells you what the real file format is independent of its file extension.

Answer 2

You have to grant permission to the folder you are trying to access through your web application. If you are using cPanel check here .

Answer 3

Late in the day but I could not find a reliable workaround. Sometimes environmental issues will affect operation. In my case I retried the action a number of times if an exception occurred. If you take this approach your action should succeed but make sure the action is idempotent.

eg in C#

Action action = () => { //call SaveImageAsCorrectFormat }
try {
  action();
}
catch
{
  try {
    action();
  catch (Exception exception) {
    //handle
  }
}