System Root

I recently had to work on a project where I needed to open an image, rotate it by 90 degrees and save it again in C#. I was having some issues where it would always save the image in the PNG format regardless of what format it was loaded from. Here’s the code that I had:

//Load the image file
Image img = Image.FromFile(filename);
//Rotate the image 90 degrees to either side
img.RotateFlip(RotateFlipType.Rotate90FlipNone);
//Save the file back over itself
img.Save(filename, img.RawFormat);
//Get rid of the object
img.Dispose();

It turns out that you can’t pass the image format into the save function directly like that. You need to save it first or it will default back to PNG format. See the following code:

//Load the image file
Image img = Image.FromFile(filename);
ImageFormat imgfrmt = img.RawFormat;
//Rotate the image 90 degrees to either side
img.RotateFlip(RotateFlipType.Rotate90FlipNone);
//Save the file back over itself
img.Save(filename, imgfrmt);
//Get rid of the object
img.Dispose();

I hope this helps someone.