[Mono-devel-list] [Patch] System.Drawing.Bitmap .NET Framework compatibility

[Ben Maurer]

On Sat, 2005-05-14 at 12:14 +0200, Kornél Pál wrote:
> Hi,
> 
> System.Drawing.Bitmap in .NET Framework implements new Bitmap(original, ...)
> constructorst as copying the original bitmap to a memory bitmap.
> 
> Mono implements it using GdipCloneBitmapAreaI.
> 
> I don't know the behaviour of Cairo but GdipCloneBitmapAreaI on GDI+ results
> in a bitmap based on the original.
> 
> As GDI+ draws bitmaps from the stream if they were created from a stream
> this different implementation of the above contructors results in
> significant difference as the stream should be closed while the bitmap uses
> it, otherwise the bitmap cannot be rendered.
> 
> BitmapFromImage is not needed for this constructor and is not recommended in
> MakeTransparent.
> 
> And not that using Dispose (that calls GC.SuppressFinalize) in
> BitmapFromImage result in memory leak as the new image will never be
> disposed.

In general, it is better to say:
        
        using (Graphics g = ...) {
        }

Which will emit the code

        Graphics g = ...
        try {
                ...
        } finally {
                if (g != null)
                    g.Dispose ();
        }

Than to just do:
        Grahics g = ...
        
        ...
        
        g.Dispose ();
        
-- Ben