C# .Net calling Graphics.FromImage(myBitmap) with certain PixelFormat throws Out of Memory Exception

Question

I was creating a little tool to do some icon drawing and I ran into an error which I cannot find an explanation for. The first PixelFormat I chose caused an Out of Memory exception. (I chose the first one in the list with an Alpha Channel: Format16bppArgb1555). Simply changing to the next alpha format down the list fixed my problem, but I was curious as to why I was getting the error, so I decided to test all PixelFormats. There are many formats which the documentation says will not work, but these 2 seem like they should.

Why do Format16bppArgb1555 and Format16bppGrayScale cause Out of Memory exceptions when calling Graphics.FromImage()?

Here is the test code I made:

    Bitmap myBitmap=null;
    Graphics myGraphics=null;

    foreach ( PixelFormat pixFormat in Enum.GetValues(typeof(System.Drawing.Imaging.PixelFormat)))
    {
        Console.WriteLine();
        try
        {
            myBitmap = new Bitmap(192, 192, pixFormat);
            Console.WriteLine("Good Bitmap" + PixFormatToString(pixFormat));
            myGraphics = Graphics.FromImage(myBitmap);

        }
        catch( Exception e)
        {
            if (myBitmap == null)
            {
                Console.WriteLine("Bad Bitmap " + PixFormatToString(pixFormat));
                Console.WriteLine(e.Message);
            }
            else
            {
                Console.WriteLine("Bad Graphics " + PixFormatToString(pixFormat));
                Console.WriteLine(e.Message);
            }

        }
        finally
        {
            if (myBitmap != null)
                myBitmap.Dispose();
            if (myGraphics != null)
                myGraphics.Dispose();
            myBitmap = null;
            myGraphics = null;
        }
    }

Here is the compressed output:

UNEXPECTED ERRORS:
Bad Graphics Format16bppArgb1555
Out of memory.

Bad Graphics Format16bppGrayScale
Out of memory.


Expected Errors Bad Bitmaps(not valid to use these PixelFormats for Bitmaps):
Undefined,Max,Indexed,Gdi,Alpha,PAlpha,Extended,Canonical

Expected Errors Bad Graphics(cannot create graphics from indexed formats):
BitmapFormat1bppIndexed,BitmapFormat4bppIndexed,Format8bppIndexed

Good Bitmaps and Graphics:
 BitmapFormat16bppRgb555
 BitmapFormat16bppRgb565
 BitmapFormat24bppRgb
 BitmapFormat32bppRgb
 BitmapFormat32bppPArgb
 BitmapFormat32bppArgb
 BitmapFormat48bppRgb
 BitmapFormat64bppPArgb
 BitmapFormat64bppArgb

Answer 1

@pinkfloydx33 has the solution in his comment:

From the docs: This method also throws an exception if the image has any of the following pixel formats... Format16bppArgb1555 Format16bppGrayScale

So they are apparently not supported by GDI+ for some reason. docs.microsoft.com/en-us/dotnet/api/…

These formats are not supported by GDI+ and there are not enough error codes to handle the reason so it throws "Out of Memory"