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

From the docs: `If the image has an indexed pixel format, this method throws an exception [...]. The indexed pixel formats are shown in the following list: Format1bppIndexed, Format4bppIndexe, Format8bppIndexed This method also throws an exception if the image has any of the following pixel formats. Undefined, DontCare, Format16bppArgb1555 Format16bppGrayScale` So they are apparently not supported by GDI+ for some reason. https://learn.microsoft.com/en-us/dotnet/api/system.drawing.graphics.fromimage?view=netframework-4.7.2#remarks — pinkfloydx33, Sep 26 '18 at 23:21
And it's not actually a real out of memory exception. It has to do with the fact that GDI only has like twenty error codes. See Hans' answer: https://stackoverflow.com/a/2610506/491907. This may help as well https://stackoverflow.com/a/4680139/491907 — pinkfloydx33, Sep 26 '18 at 23:24
@pinkfloydx33 It actually throws a different error for Indexed PixelFomats: "A Graphics object cannot be created from an image that has an indexed pixel format." - thanks for the link to the expected behavior, even though they don't explain why! — Ves, Sep 27 '18 at 02:17

score 1 · Accepted Answer · answered Sep 28 '18 at 15:21

@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. learn.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"

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

1 Answers1