Visual C++, System Argument Exception in System Drawing (Windows Form) - image

Question

This error shows up when run the program and try to load an image:
A first chance exception of type 'System.ArgumentException' occurred in System.Drawing.dll
An unhandled exception of type 'System.ArgumentException' occurred in System.Drawing.dll
Additional information: The parameter is invalid.
Here is my code:
Basically, there is a numericUpDown, a button, an openFileDialog and a pictureBox. The user changes the numericUpDown's value, depending on which picture he wants to load (the user doesn't have to open the openFileDialog). For example, if the user chooses "3" as a value for the numericUpDown, the FileName of the openFileDialog will be:
Public:
void Set_FilePath()
{
int n = (int)numericUpDown1->Value;
switch (n)
{
case 1: openFileDialog1->FileName = "C:\Users\Public\Pictures\Sample Pictures\Chrysanthemum.jpg"; break;
case 2: openFileDialog1->FileName = "C:\Users\Public\Pictures\Sample Pictures\Desert.jpg"; break;
case 3: openFileDialog1->FileName = "C:\Users\Public\Pictures\Sample Pictures\Hydrangeas.jpg"; break;
case 4: openFileDialog1->FileName = "C:\Users\Public\Pictures\Sample Pictures\Jellyfish.jpg"; break;
case 5: openFileDialog1->FileName = "C:\Users\Public\Pictures\Sample Pictures\Koala.jpg"; break;
case 6: openFileDialog1->FileName = "C:\Users\Public\Pictures\Sample Pictures\Lighthouse.jpg"; break;
case 7: openFileDialog1->FileName = "C:\Users\Public\Pictures\Sample Pictures\Penguins.jpg"; break;
case 8: openFileDialog1->FileName = "C:\Users\Public\Pictures\Sample Pictures\Tulips.jpg"; break;
}
}
private: System::Void button1_Click(System::Object^ sender, System::EventArgs^ e) {
Bitmap^ myImage;
Set_FilePath();
myImage = gcnew Bitmap( openFileDialog1->FileName );
pictureBox1->SizeMode = PictureBoxSizeMode::StretchImage;
pictureBox1->Image = dynamic_cast <Image^> (myImage);
}
My attempt to fix it:
I thought that i didn't copy the directions of the images correctly. So i changed the code to:
if(openFileDialog1->ShowDialog() == System::Windows::Forms::DialogResult::OK)
{
MessageBox::Show(openFileDialog1->FileName);
myImage = gcnew Bitmap( openFileDialog1->FileName );
pictureBox1->SizeMode = PictureBoxSizeMode::StretchImage;
pictureBox1->Image = dynamic_cast <Image^> (myImage);
}
This is working perfectly. Also, a messagebox that shows the filename of openFileDialog is appeared... The directions of the images that are correct... I don't know what is wrong with my program. The problem is that i don't want the openFiledialog to be appeared.
(I am using Visual Studio C++ 2010, the application is made in windows form), Any help would be appreciated.
Thanks..

Answer 1

Exceptions raised by the Image and Bitmap classes are not very informative. You can get an "The parameter is invalid" exception for several reasons. It could be an image file that's corrupted, not that likely in your case since you are using stock Windows image files. It can also be caused by an image that's too large to fit in the available virtual memory address space. You'd like an OutOfMemoryException but GDI+ is goofy about it.
That's the more likely cause, your program is pretty likely to bite the dust like that when you run it for a while. Images can require a lot of unmanaged virtual memory to store their pixel data. And that should be released when you no longer use the image. The garbage collector will do that for you, but it isn't all that quick about it. Certainly an issue with the Bitmap class, it uses very little GC heap so isn't terribly likely to trigger a garbage collection often enough to keep you out of trouble.
Which is why it implements the IDisposable interface. The Dispose() method gets that memory released early. You are not calling it.
You'll need to fix that in your code, like this:
delete picureBox1->Image;
try {
myImage = gcnew Bitmap( openFileDialog1->FileName );
pictureBox1->Image = myImage;
}
catch (Exception^ ex) {
pictureBox1->Image = nullptr;
MessageBox::Show(ex->Message);
}
Note the added delete operator call, that's the one that calls IDisposable::Dispose(). It gets rid of the old image, the one you don't need anymore because you are going to display another image. The try/catch ensures that your program keeps running when the chips are down, dealing with a bad image file or a monster one that just can't fit in available memory. The kind that you deal with by targeting x64 so you get a 64-bit program.