Code archives/Graphics/Chiaroscuro/greyscale buffer
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| Reading Calvin & Hobbes, I found the strip where Calvin's dad says he sees everything in black and white; the strip is drawn with chiaroscuro shading, where you choose black or white only, depending on a brightness threshold (so it works best on high contrast images). I had to convert to greyscale on the way anyway, so that option is there... Greyscale:  Chiaroscuro:  It's slow, but it amused me to do the Calvin thing, and it could actually be useful for pre-rendering if you want to offer a real-time greyscale option (load image, greyscale its buffer, ta-da)! Try pasting the code below at the top of the "samples\mak\dragon\dragon.bb" demo supplied with Blitz3D, adding this line just before Flip: GreyScale GraphicsBuffer (), GraphicsWidth (), GraphicsHeight (), 0 Change the 0 on the end to 40 for a reasonable chiaroscuro effect! With the 0 changed to around 40, you can try the "fastest Spectrum 48k on earth" effect if you run it in 320 x 200 @ 16-bit fullscreen if possible. Also, 320 x 200 @ 32-bit is the fastest mode here... |
; chiatol parameter -- 0 for greyscale, 1-255 for chiaroscuro effect tolerance threshold... Function GreyScale (buffer, width, height, chiatol = 0) tbuffer = GraphicsBuffer () SetBuffer buffer LockBuffer buffer For x = 0 To width - 1 For y = 0 To height -1 rgb = ReadPixelFast (x, y) r = rgb Shr 16 And %11111111 g = rgb Shr 8 And %11111111 b = rgb And %11111111 trgb = (r + g + b) / 3 If Not chiatol r = trgb g = trgb b = trgb Else If trgb < chiatol r = 0 g = 0 b = 0 Else r = 255 g = 255 b = 255 EndIf EndIf rgb = ((r Shl 16) + (g Shl 8) + b) WritePixelFast x, y, rgb Next Next UnlockBuffer buffer SetBuffer tbuffer End Function |