Converting 32 bit to 16 bit

Jiia · 2002-09-04T03:35:40

There's not much to ramble &#111n about. I'm just trying to find the fastest way to render a 32 bit image to a 16 bit destination. This is the fastest I've tried so far. The &#111nly variables not set in this function are the RPixShR,RPixShG,& RPixShB. They are equal to the number of bits a 255 color value needs to be shifted over to the right for the 16 bit screen value, and are used to dump off the extra bits. Also, the XRes & YRes are the screen resolution.ULONG *Src = Page->Bits; // Custom back buffer USHORT *Des = (USHORT*) SurfaceDesc.lpSurface; // the real back buffer LONG ExSpan = (SurfaceDesc.lPitch>>1) - Setup.XRes; LONG y = Setup.YRes; LONG x; INT R16s = RPixShR; INT G16s = RPixShG + 8; INT B16s = RPixShB + 16; while(y--) { x = Setup.XRes; while(x--) { *Des = USHORT( ((((*Src) & 0x000000FF) >> R16s) << LPixShR) | ((((*Src) & 0x0000FF00) >> G16s) << LPixShG) | ((((*Src) & 0x00FF0000) >> B16s) << LPixShB)); Src++; Des++; } Des += ExSpan; // Any Extra Pitch } I would have never thought this method would be the &#111ne that won my timing, but it did. But it is still not very fast. Does anyone know of a good method of doing this? The Destination is usually going to be video memory, so I would think the best aproach would be to do as little as possible with it. [edited by - Jiia &#111n September 1, 2002 12:00:44 AM]

Graphics and GPU Programming Programming

Started by Jiia September 01, 2002 10:51 PM

9 comments, last by Jiia 21 years, 7 months ago

JonnyQuest

331

September 04, 2002 03:35 AM

A straight copy from sysmem to vidmem is pretty fast, but if you do per-pixel operations, it''s slow as hell.
What I do for 2D stuff is just do everything in system memory, have a system memory "back" buffer the same format as the primary surface and just update that, and copy it to the primary surface at the end of the screen. It''s bound to be fast, cause that''s how they did it back in the VGA days

- JQ
Full Speed Games. Coming soon.

~phil

Converting 32 bit to 16 bit

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Converting 32 bit to 16 bit

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