mfc, Erase a line in CBitMap

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mfc >> Erase a line in CBitMap

by lynnzyeo » Tue, 21 Mar 2006 19:46:22 GMT

Hi, got a problem here. Say I have drawn a yellow line on a black
background cbitmap. The background of the bitmap will have some grids,
which are blue. Is there any way to erase the yellow line such that the
grids are unaffected? Any ideas? Thanks in advance.


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mfc >> Erase a line in CBitMap

by Ajay Kalra » Tue, 21 Mar 2006 22:28:56 GMT


I dont think this is possible at GDI level. Ultimately its all pixels.
If you have this line as an object, you can put some methods in it
which erases the object by XORing etc. If you are using OpenGL/DirectX
etc, there may be some methods to do it as well.

--------
Ajay Kalra
XXXX@XXXXX.COM



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mfc >> Erase a line in CBitMap

by AliR » Tue, 21 Mar 2006 23:57:17 GMT

If you want to allow users to deleted some drawings after they have been
drawn, you will need to keep your drawings as objects instead of directly
drawing to the DC as the user draws.

For example. You will need to have a class for everything that you allow the
user to draw (Rectangles, Circles, lines,....)
As the user draws, you need to create one of these classes and store it in
an container class (array works well, if you care about zorder). When you
need to redraw the graphics, loop through the container, and tell each one
to draw itself. When you want to delete an item (like a line) simply remove
it from the list, and redraw the screen.

AliR.






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