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Possible algorithm for converting photos to NES
http://forums.nesdev.com/viewtopic.php?f=21&t=13167
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Author:  tepples [ Thu Aug 27, 2015 11:17 am ]
Post subject:  Re: Possible algorithm for converting photos to NES

This duotone technique resembles the process I used when trying to make NES-style portraits of #nesdev regulars.

The hardest part is automatically coming up with a palette, and the LBG algorithm described above might work well.

Author:  Sik [ Thu Aug 27, 2015 11:42 am ]
Post subject:  Re: Possible algorithm for converting photos to NES

dougeff wrote:
Maybe I should explain how to do a duotone, since the Wikipedia page doesn't...

First you turn the image into a black and white. Then instead of shades of gray in the palette, you use shades of pink (faces) or shades of blue (other things).

This description seems off (you just described variants of monochrome), duotone is more like converting it to a two-channel color format (instead of three-channel like RGB). On the NES, that'd be like treating the tiles as two 1bpp channels instead of a single 2bpp one (and you'd need to resort to dithering too).

At which point just plain grayscale 2bpp with dithering is a better choice, just using a different hue/saturation for the shades.

Author:  dougeff [ Thu Aug 27, 2015 12:15 pm ]
Post subject:  Re: Possible algorithm for converting photos to NES

Here's what I mean. Trust me I've made 100+ duotone images over the years...

1. Color photo
2. convert to black and white
3. convert to duotone
4. convert to NES 4 color palette

And you don't really need step 3, I just included it to demonstrate an actual duotone image.

Attachments:
duotone1.jpg
duotone1.jpg [ 25.91 KiB | Viewed 644 times ]
duotone2.jpg
duotone2.jpg [ 67.58 KiB | Viewed 644 times ]

Author:  dougeff [ Thu Aug 27, 2015 12:28 pm ]
Post subject:  Re: Possible algorithm for converting photos to NES

(Edit)

My point, is that the final product will LOOK like a duotone, not that you need to use these steps to get there.

Author:  tokumaru [ Thu Aug 27, 2015 1:39 pm ]
Post subject:  Re: Possible algorithm for converting photos to NES

dougeff wrote:
I don't expect to see full color pictures, but anime style flat images and reduced color images could be a possibility.

Yes, and my point is that you can already make those kinds o images with decent results if you do things manually. Automating the process might make it faster, but it won't generate better results than what good artists usually produce.

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