GDI+ questions

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Hi,

I'm using GDI+ api to draw a day time planning into a picture, it's great,
very fast and import of png with transparency is very neat.

I have one problem, 90% of the time, I don't need to redraw all the picture,
the background is the same and only the items on it changes.

I would like to make a copy of this background and when I need it redraw it
using GdipDrawImageRectRectI (which I use to draw items on my planning and
work very well) instead of redrawing completly the background using
rectangle, line, ... functions.

I tried a lot of thing to save a copy of my background before drawing the
items (GdipCreateBitmapFromGraphics, GdipSaveImageToFile, ...) but I'am not
able to get this background saved. For example, the function
GdipCreateBitmapFromGraphics send back 0 (everything ok) but when I try to
draw the resulting image, nothing. (actually, I save the picture box on the
disk using dev tools native function and redraw the background using
GdipLoaImageFromFile/GdipDrawImageRectRectI combo wich is quite slow)

Do you have any idea of what I am doing wrong ?

My second problem is to refresh the screen after drawing. I tried API like
InvalidateRect, InvalidateRgn, ... to no avail, if I move another windows on
top of my program and then remove it ... the screen refresh correctly (my
software development tools don't have redraw property, I must use an API)

Any help will be much apreciated.

As English is not my native language, if you need me too explain better,
please ask.

Many thanks,

Albert P.


.

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