myBitmap.RawFormat is something different than any known ImageFormat?

Question

I'm working with GDI+ and I create a new bitmap like this:

var bmp = new Bitmap(width, height);

now when I observe its RawFormat.Guid I see that it is different from all predefined ImageFormats (while I expect it to be JPEG).

ImageFormat.Jpeg.Guid
    {b96b3cae-0728-11d3-9d7b-0000f81ef32e}
format.Guid
    {b96b3caa-0728-11d3-9d7b-0000f81ef32e}

Interesting part is that as you can see they are identical except one character which makes me even more confused.

Any idea why? Which parts of code determines what is the RawFormat of the bitmap I create? How can we ensure it's a valid ImageFormat?

Thanks.

Answer 1

From the Windows SDK, <gdiplusimaging.h> header file:

DEFINE_GUID(ImageFormatUndefined, 0xb96b3ca9,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatMemoryBMP, 0xb96b3caa,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatBMP, 0xb96b3cab,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatEMF, 0xb96b3cac,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatWMF, 0xb96b3cad,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatJPEG, 0xb96b3cae,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatPNG, 0xb96b3caf,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatGIF, 0xb96b3cb0,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatTIFF, 0xb96b3cb1,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatEXIF, 0xb96b3cb2,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);
DEFINE_GUID(ImageFormatIcon, 0xb96b3cb5,0x0728,0x11d3,0x9d,0x7b,0x00,0x00,0xf8,0x1e,0xf3,0x2e);

"Memory BMP", quite appropriate. And yes, Microsoft often messes with GUIDs by hand. Naughty.