Scrolling large bitmaps

Use DirectX for BLTing should speed things vs. the VCL. If you don''t want to use DX, try looking up DRAWDIB and some of the other DIB drawing commands that were introduced in Win95 and WinG.



[ turbo | turbo.gamedev.net ]

Thanks - guess I may have to give in and go the DirectX way.

A bitmap of that size would need to be loaded from disk in sections. If that one bitmap was in 24-bit colour, then 7500 pixels x 3500 pixels x 3 bytes per pixel = 75MB. That''s a lot of bitmap to load in one go and keep in memory.

I would suggest breaking the bitmap up into smaller, more manageable chunks. Say 256x256. Load each section as necessary and discard unneeded sections. That would be your most efficient solution.

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Steve 'Sly' Williams
Tools Developer
Krome Studios

The bitmap is reduced to 8bit colours, which helps a lot (down to 24Mb only). Still plan to chop it into bits though.

Thanks for the help.

Edited by - strategy on September 18, 2000 7:08:04 AM

Hi there,

you can always create a DIB and stream the required data into
the color buffer from your graphics file.Doing this cuts down dramatically on memory usage but not much on speed as windows
uses its swap files on disk anyway.In fact I used this method
and performance was exactly the same.

Hope this idea may help.