Ancestors

Written by demofox on 2025-01-20 at 20:27

Quantizing an image to 2 bits per color channel (64 colors). Dithering with 8x8 bayer (top) and FAST spatiotemporal blue noise (bottom).

Randomly offsetting bayer each frame, it doesn't converge.

That is weird.

The bayer matrix averages to 0.5 so is unbiased in that regard.

I think it must be due to Bayer having 1/64th values, while the blue noise has 1/256th values.

hmm...

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Written by demofox on 2025-01-20 at 20:29

Bayer totally bites it at 1 bit per pixel (8 colors), with a 2x4 matrix. FAST STBN works just fine.

(I'm working on a dithering & stippling blog post)

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Written by demofox on 2025-01-20 at 20:35

At 3 bits per color it doesn't converge either though. Still ugly banding in the sky. That's 512 values, so is 1/512. Something else must be going on.

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Written by demofox on 2025-01-20 at 21:41

oops, 3 bits per color channel is 512 colors, but not 512 values in the bayer matrix. Each channel is treated independently, so this is just a 4x2 bayer matrix = 8 values (shades).

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Toot

Written by demofox on 2025-01-20 at 21:46

Yeah mystery solved... it's the quantized values used in Bayer that are causing the banding.

Here the image is dithered and quantized to 2 bits per color channel. Top is white noise limited to 4 discrete values. Bottom is white noise with full range of floating point values.

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Descendants

Written by Tariq on 2025-01-20 at 21:50

@demofox

Looks interesting - I don't fully understand it but looking forward to your post!

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