Dithering idiot...

-=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- (c) WidthPadding Industries 1987 0\|694\|0 -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=-
Socoder -> Handheld Coding -> Dithering idiot...
Thu, 12 Jun 2008, 05:57
spinal	For something to do, I have decided to have a go at image dithering, the NDS uses 15nit gfx, but although it looks good, it does not offer the best image quality. I want to convert a regular 24bit image to a 15bit one for use on the ds, currently I'm doing this by dividing the colour values, which, although does the job, you can see banding on gradients etc. so I want to dither them but I haven't much of a clue where to start. I did have a little go a few years ago using a 16 colour palette, in which I pre-calculated colour combinations by hand for an ordered dither, but doing that with thousands of colours doesn't sound like fun to me. Anyone got any ideas on doing this? -=-=- Check out my excellent homepage!
Thu, 12 Jun 2008, 07:28
Jayenkai	Always something I wished PaintShopPro could do, but it's dithering either ends up as garbled pixels, or all plain colors, meaning that when you send it to the DS, you end up back at the banding again. Nngh.. So, taking your request as somewhat of a challenge. (And I love my challenges!) Graphics 800,600,32,2 SetBuffer BackBuffer() in=LoadImage("input.png") Global ReadIn#=256 Global DropTo#=32 ;If Random dithering's a bit dodgy, play with these two numbers Global Threshold#=0.3 Global Additive#=0.2 ;Dither Types : 0 = Banding, 1 = Random, 2 = Ordered Global DitherType=1 Dim OrderMatrix#(2,2) OrderMatrix(0,0)=0.8 OrderMatrix(1,0)=0.3 OrderMatrix(2,0)=0.4 OrderMatrix(0,1)=0.6 OrderMatrix(1,1)=0.1 OrderMatrix(2,1)=0.2 OrderMatrix(0,2)=0.7 OrderMatrix(1,2)=0.5 OrderMatrix(2,2)=0.9 For x=0 To ImageWidth(in) DrawImage in,0,0 Flip SetBuffer ImageBuffer(in) LockBuffer ImageBuffer(in) For y=0 To ImageHeight(in) argb=ReadPixelFast(x,y) r#=((argb And $FF0000) Shr 16) / (readin/dropto) g#=((argb And $00FF00) Shr 8 ) / (readin/dropto) b#=((argb And $0000FF) Shr 0 ) / (readin/dropto) userI=Get(r#,x,y) Shl 16 usegI=Get(g#,x,y) Shl 8 usebI=Get(b#,x,y) WritePixelFast x,y,(255 Shl 24)+userI+usegI+usebI Next UnlockBuffer ImageBuffer(in) SetBuffer BackBuffer() Next Cls DrawImage in,0,0 Flip WaitKey() Function Get(infloat#,x,y) outfloat#=Floor(infloat#) bit#=(infloat#-outfloat#) If DitherType=1 bit#=bit#+Rnd(-Additive,Additive) If Rnd(bit)>Threshold Then outfloat=Ceil(infloat#) EndIf If DitherType=2 If bit=>OrderMatrix(x Mod 3,y Mod 3) Then outfloat=Ceil(infloat#) EndIf OutInt=outfloat*(readin/dropto) If OutInt<0 Then OutInt=0 If OutInt>255 Then OutInt=255 Return outint End Function --v You might want to stick a "SaveImage" on there, too! Note, you can even play with the "DropTo" figure to make nice monochromed pixelly pictures, too! This was where the OrderMatrix came from! -=-=- ''Load, Next List!''