An age old question, I''m sure. Unfortunately, the search is broken or down or both, and I''m lost So here goes... I''m trying to work on some kind of graphics engine, and I need the abiltiy to plot pixels. Ideally, I want to send a RGB value and have my pixel appear correctly (much like I do with the aptly named SetPixel function in GDI... only not in GDI) I''m using TOWGPG because I figure, if I can''t copy his code and make it work, I sure can''t write my own. So I''m slapping his code as placeholder code for now, basically, just for the pixel plotting routines. This is what he does: #define RGB16(r,g,b) ((b%32) + ((g%64) << 5) + ((r%32) << 11)) I really don''t understand this part. What exactly is the result of this? It''s supposed to generate some code for a 16bit pixel plot but I am not sure what it does. I have assumed the << are bitshifts? but even if they are, I don''t know what they do very well. I''d apprciate help on this piece. But anyway, after that, LaMothe writes: surfaceMemory[(int)x+(int)y*(memPitch >> 1)] = RGB16(red, green, blue); The variable surfaceMemory is a USHORT pointer to the surface from the DDSURFACEDESC2 structure, and memPitch is an int pointer to the lPitch. I use this, call the function, and low and behold, it plots. The only problem is, my image displays wrong. It is discernible, but the colors are off. A little background... I wrote the image format myself (kind of). Basically, it reads in a red, green, then blue RGB code, and does that for the entire size of the image. I have double checked the loading code by reloading it into my image editor and in the image editor, it displays normally (the image editor is written using GDI pixel plotting routines) Anyone have an idea why I can''t get LaMothe''s code to work, or perhaps a better idea? Peon

RGB16BIT555(r,g,b) ((b&31) + ((g&31) << 5 ) + ((r & 31) << 10))
RGB16BIT565(r,g,b) ((b&31) + ((g&63) << 5) + ((r&31) << 11))

RGB32BIT(a,r,g,b)((b&255)+((g&255) << 8) +((r&255) << 16) + ((a&255) <<16))


To plot:
16Bit:

//use something to decide which mode your in...//i''ll assume 565..//x and Y are ints...SurfaceMemory[(y*(SurfacePitch >> 1) + x] = RGB16BIT565(0,0,0);32Bit:SurfaceMemory[(y*(SurfacePitch >> 2) + x] = RGB32BIT(0,0,0,0); 

hope this helps...

Alright, I just want to say first of all, thanks for the help I tried some of the suggestions found here, as well as the link to the 16 pixel plot article. Unfortunately, I'm still having the same problem (the tutorial was also a bit beyond my level, thoughI will continue to look at it) I decided to post a picture to show better what the problem is; maybe someone will see the colors and figure out exactly what is wrong.

NOTE: I am using an image anonimizer, so it is possible that the pictures will either run slow, or exceed the bandwitdth limit; bear with me, I have no good, free webspace



(This one is supposed to be a rainbow; note how the red, green, blue colors are correct, but the rest are not)

EDIT: I added an original; broken version. On second glance, the green and blue ARE slightly off the original version... this might be due to less shades though. The original was done with the RGB() macro and the GDI SetPixel function.



A blue gradient, from light to dark. Original is the top right one; the "broken one" is the lower left. Notice how the gradient looks ALMOST right, but almost like on the wrong "cycle".

Any ideas from these screenshots? It's definetly plotting, but the colors are still off

Peon

[edited by - Peon on March 18, 2003 8:06:19 PM]

[edited by - Peon on March 18, 2003 8:06:37 PM]

[edited by - Peon on March 18, 2003 8:11:57 PM]

Just a quiet bump... I promise I''ll only do it once

Peon