dotnet drawing api: (This question might pertain as much to GDI+ as to drawing in the .NET
drawing framework.)

I'm working in C#, drawing to a Graphics object initialized by a
handle of an enhanced metafile. When filling a path with a brush
created by

SolidBrush sb = new SolidBrush(FillColor);
g.FillPath(sb, MyPath);

the result appears dithered on the resulting metafile. The FillColor
was created by an ARGB value (alpha and RGB). The alpha value in
FillColor is intermediate between 0 and 255.

The dithering does not seem necessary. When the resulting metafile is
played against a solid background, most of the dots seem to be
correctly blended with the background color. Yet the remainder of the
dots are in a dithered pattern.

The size of the dither pattern varies according to the target
environment (screen or bitmap). It appears to be a fixed number of
pixels.

Here is my question: How can I draw with a solid color, with an
intermediate (semitransparent) alpha value, onto a Graphics object so
that it won't dither on an enhanced metafile?

EMF corresponds to GDI, in which the only support for alpha channel is
AlphaBlend. But AlphaBlend is not supported on all Win32 OSes. So GDI+ can't
safely use AlphaBlend. That is the reason for using mask bitmap to simulate
alpha channel. This also happens during printing. So you can say it's
by-design.

--
Feng Yuan (www.fengyuan.com)

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