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Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 6:54 pm
by thefox
dougeff wrote:Bank swapping mid-frame?
Yeah it does mid-screen bank switches and also switches the nametable to get an 8x16 color attribute area.

Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 9:43 pm
by dougeff
Here's another try. This time I resized to 128 high, boosted saturation to +75%, boosted constrast +40%, lightened the eyes and nose, made a special 4 color swatch set by eyedropping on 4 places on the canvas (note, these are not the final colors), mode/indexed color, use the custom swatch as the palette, dither 40%. touched up the eyes again with pencil tool.

copy. paste into YY-CHR. It looks nicer with at least 1 complementary color.

Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 9:49 pm
by dougeff
I also made this. An attempt at full color by rotating between red, green, and blue quickly. However, it's flickery as hell. And the color quality is lacking. Done by bank swapping and palette changes every frame. I can't post a still frame because it would only show 1 color.

Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 9:56 pm
by dougeff
thefox wrote:
dougeff wrote:Bank swapping mid-frame?
Yeah it does mid-screen bank switches and also switches the nametable to get an 8x16 color attribute area.
Thanks for responding. I may try to reverse engineer this technique, it looks great.

Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 10:04 pm
by tokumaru
One of the best ways to display full color pictures on the NES I have ever seen is tepples' rgb121. It uses flickering to alternate between the green channel (2 bits) and the red/blue channels (1 bit each). Flickering is a sensitive topic though, since HDTVs can't agree on a standard way to handle it. The variant that alternates channels every scanline should look decent in most cases, I guess.

Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 10:18 pm
by thefox
tokumaru wrote:One of the best ways to display full color pictures on the NES I have ever seen is tepples' rgb121. It uses flickering to alternate between the green channel (2 bits) and the red/blue channels (1 bit each). Flickering is a sensitive topic though, since HDTVs can't agree on a standard way to handle it. The variant that alternates channels every scanline should look decent in most cases, I guess.
tepples: The link (http://pics.pineight.com/nes/rgb121.zip) you posted at that thread is broken.

Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 10:47 pm
by tokumaru
Actually, the rgb121 method works quite well even without the flicker. Just by alternating the green channel with the red/blue channels every scanline you can get a pretty colorful image. I tried one of the most colorful pictures I could think of, which is a Super Sentai team:
liveman-original.png
liveman-original.png (132.11 KiB) Viewed 5726 times
And here are the individual rgb121 frames generated from that picture:
liveman-a.png
liveman-a.png (9.97 KiB) Viewed 5726 times
liveman-b.png
liveman-b.png (10.07 KiB) Viewed 5726 times
In both pictures the colors of the rangers are represented accurately enough, so even without the flicker the results are pretty decent compared to approaches that use a single name table.

Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 10:50 pm
by tokumaru
And here's the animated GIF:
liveman-flicker.gif
liveman-flicker.gif (21.01 KiB) Viewed 5725 times
It'll probably look better in a TV running at a proper 60Hz, unlike browsers do with GIF animations.

Flicker or no flicker, I'd say this is up to par with most FMV sequences found in Sega CD games.

BTW dougeff, if you can, don't use JPG for images with flat colors or retro game art in general. Not only is the final size usually bigger than that of a PNG or a GIF, but the lossy compression algorithm introduces a lot of artifacts all throughout the images.

Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 11:05 pm
by thefox
It does look good. Makes me want to play around with this technique for a bit. Was there ever a ROM made that does the per-scanline nametable switch?

Re: How to convert a photo to NES format

Posted: Wed Jul 15, 2015 11:15 pm
by tokumaru
thefox wrote:Was there ever a ROM made that does the per-scanline nametable switch?
Yes. I just found tepples' demo on my hard drive:
rgb121.nes
(256.02 KiB) Downloaded 282 times
BTW, the forum logged me out when I tried uploading the .zip... is this normal?

Re: How to convert a photo to NES format

Posted: Thu Jul 16, 2015 6:21 am
by tepples
thefox wrote:tepples: The link (http://pics.pineight.com/nes/rgb121.zip) you posted at that thread is broken.
Not anymore. Thank you for reporting it.

(If your monitor doesn't sync up right, compare the original pics.)

Re: How to convert a photo to NES format

Posted: Thu Jul 16, 2015 9:30 am
by Sik
tokumaru wrote:Flickering is a sensitive topic though, since HDTVs can't agree on a standard way to handle it. The variant that alternates channels every scanline should look decent in most cases, I guess.
This is probably the one situation where forced deinterlacing would actually be useful.

A much bigger problem would be people with epillepsy, honestly =P

Re: How to convert a photo to NES format

Posted: Sat Jul 18, 2015 5:54 am
by dougeff
Here's a full screen example using MMC3 scanline IRQs to bankswap 3 times per frame. Not as impressive as thefox because I'm only using 1 palette for everything. I was getting glitches on my first few tries, when I simply counted the right number of lines and switched, so I had to subtract 1 from the scanline count, and then wait about 110 cycles so that the swap happened during h_blank.

I don't seem to be able to use scanline counting to switch nametables at every scanline, I think I'll try again with a big wait loop. Is the timing something like this...wait for v_blank, wait till not v_blank, 114 cycles switch / 114 cycles switch / 113 cycles switch / repeat. ?

Re: How to convert a photo to NES format

Posted: Sat Jul 18, 2015 6:34 am
by ccovell
Looks nice. 4 colours is not so bad... reminds me of what I did back when on my old page. Mine used the CNROM mapper with cycle-timed code and/or sprite 0 hit.

ImageImageImageImage

Re: How to convert a photo to NES format

Posted: Sat Jul 18, 2015 7:00 am
by dougeff
Ooh, Moby 'everything is wrong'...that takes me back. Did you ever hear the DJ remix album of that, some of Moby's best work.

Yeah, 4 colors can do a lot. I like those.