Bitmap

I have created a bitmap. Now I have to give the facility to zoom the bitmap by 200% or 400% as the user desires.It's very much like mspaint. Please tell me how to do it.

[Walter I An]

Will StretchBlt() function help?

Good luck with Painting!!

Walter An

[Jerry Coffin]

You've got a couple of options. One is to use StretchBlt to draw the bitmap, specifying a target area twice as wide and twice as wide as the original area (or, of course, 4 times in each direction to do 400%).

If this is an editing program, you'll want to be able to know which of the original pixels the user is clicking on. In that case, you may prefer to do the zooming by changing the mapping mode. This way, when the user clicks on the display, you can easily convert from the point on the display to a coordinate in the original bitmap using DPtoLP.


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