155 replies to this topic

[doron]

Hi guys

You can't stop progress, can you?

Since I began this thread, I would like to be the fist to suggest a picture for the upcoming slideshow demo. It's a girl I once knew.

you are great
dor-x

P.S And if somone can explaine in non-computer english what exacly have you done, and why is the picture still small?

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[raindog]

Nukey Shay said:

When I mentioned "combined", I mean displaying them side-by-side.  The player objects are 8 bits wide, and missiles 2...this gives you 20 pixels across (40 if re-used once each).  As with screen pixels, the sprites can be colored independantly on each scanline, right?  So you could create pictures with smaller "pixels" (the P/M bits)...which would look better on-screen than using the background pixels.

The demos Thomas and Andrew have done in recent days do use the players, multiplexed 6 times as in many games' score display routine. I guess you could add both missiles and get 50 pixels instead of 48

Rob

[Nukey Shay]

Exactly...that would be the same resolution as the pictures using the background pixels (and use the same amount of memory for the bitmaps), but would look better IMO due to the smaller pixel size.

[ZylonBane]

Nukey, where did you get the idea that anyone was talking about using playfield pixels? This has been based off the 48-pixel "6-digit-score" routine the whole time.

[Nukey Shay]

Ooooh!

I dunno...I was trying to follow the thread, but A26 refuses to run the demos.

[Paul Slocum]

Shot:

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[ZylonBane]

doron said:

I would like to be the fist to suggest a picture for the upcoming slideshow demo. It's a girl I once knew.

Umm, don't you think it would make more sense to include pictures that more than one person would recognize? You know, stuff like this--

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[Albert]

I almost spit out my drink at the kitty one.. And mmmmmmmm, System Shock!!

..Al

[Nukey Shay]

[MegaManFan]

That is SO wrong.

[Thomas Jentzsch]

raindog said:

The demos Thomas and Andrew have done in recent days do use the players, multiplexed 6 times as in many games' score display routine.  I guess you could add both missiles and get 50 pixels instead of 48

idea: In theory that would even give you 54 pixels (because the missiles are multiplexed too). But there isn't enough CPU time for the extra code required. The 2600 can barely handle the current routine, there is not a single cylce left in my code (well, with some loop unrolling I might gain a few cycles, but not enough by far).

[Thomas Jentzsch]

ZylonBane said:

You know, stuff like this--

How about some more cartoon like pictures? I guess they might look even better when converted.

[Nukey Shay]

You mean like those slideshow carts on the Snes?


Just go easy on the tentacles, please :P

[Thomas Jentzsch]

Nukey Shay said:

You mean like those slideshow carts on the Snes?

I don't know them. Pictures?

[Nukey Shay]

Urm...I don't think that the Al's would like that


(I was referring to carts like the Wesley Girl series, Lion's Sex Show, etc.)

[Thomas Jentzsch]

ZylonBane said:

2. Load a custom palette I've created that only contains RGBCMYKW (slightly desaturated), using error diffusion dithering.

Since the 2600 can only produce 128 colors, shouldn't the palette RGB values be adapted to the possible 2600 palette values?

And if a picture doesn't require 100% black or white, how would that influence the optimal values?

[ZylonBane]

It's weird but, for the purposes of this display technique, the 2600 palette is completely irrelevant except for Red, Green, and Blue. This is because, just like the monitor phosphors, all other colors emerge from combining these three. So, you can see white in an image even though the 2600 is never displaying white in any given frame.

The custom palette on the PC side represents nothing more than all the possible combinations of RGB, and is only a convenience to ensure that the dither pattern is in sync for all three layers. It lets you dither, then split to RGB, as opposed to splitting and then dithering.

You could create images that only interlaced two colors, but they would be very limited, eg-- Red-Green would only give you red, green, yellow, and black.

It took me a while to get a firm mental handle on all this back when ColorView first came out for the 8-bits. Just forget about the palette and think of it as managing your own jumbo RGB phosphor triads.

[Thomas Jentzsch]

ZylonBane said:

It's weird but, for the purposes of this display technique, the 2600 palette is completely irrelevant except for Red, Green, and Blue.

Ok, I try to explain a bit more detailed:
Shouldn't those three RGB values the 8 color palette is based on be adapted to the later selected 2600 three colors? Right?

And since you flicker the colors with 20Hz, you need to increase the brightness of each 2600 color, else the resulting picture would be too dark. But then you shouldn't use saturated colors in the 8 color palette. Right?

And if the maximum amount of e.g. Red in a picture is quite low, wouldn't it make sense to choose different values for Red then. Right?

And if the picture is quite dark, wouldn't generally darker RGB colors be better? Right?

[ZylonBane]

Ah, I see where you're coming from.

What you say is true, but doesn't matter because this system has such incredibly pitiful color resolution that subtlety just doesn't enter into it. The test images I did above, I got the best results by cranking the brightness and saturation up to cartoony levels before converting. The only reason I desaturated my palette was to get a general preview what the end result would look like. I could have used pure RGB combos and still gotten the same color splitting... when there's only one red to choose from, the paint program doesn't care how saturated it is, just that it's the closest match.

I suppose if you had some pics that were all dim or all bright and desaturated then it would be worthwhile to tweak the RGB that way, but those would be special cases.

And as for this-- "And if the maximum amount of e.g. Red in a picture is quite low, wouldn't it make sense to choose different values for Red then. Right?"

If I'm understanding what you're saying here, then NO. If a picture has no red in it, but it does have white, then you still need the red to create the white. The same goes for all the other color combinations.

[Thomas Jentzsch]

ZylonBane said:

when there's only one red to choose from, the paint program doesn't care how saturated it is, just that it's the closest match.

Yup, but the dithering error will be different, so the final image will be different too.

Quote

If I'm understanding what you're saying here, then NO. If a picture has no red in it, but it does have white, then you still need the red to create the white. The same goes for all the other color combinations.

I meant the maximum value for the RGB channel. A White has a quite high value in all three channels.

BTW: Attached is my Baboon demo. Enjoy!

Attached Files

•  baboon.zip   1.84K   72 downloads

[Andrew Davie]

Thomas Jentzsch said:

ZylonBane said:

It's weird but, for the purposes of this display technique, the 2600 palette is completely irrelevant except for Red, Green, and Blue.

Ok, I try to explain a bit more detailed:
Shouldn't those three RGB values the 8 color palette is based on be adapted to the later selected 2600 three colors? Right?

And since you flicker the colors with 20Hz, you need to increase the brightness of each 2600 color, else the resulting picture would be too dark. But then you shouldn't use saturated colors in the 8 color palette. Right?

And if the maximum amount of e.g. Red in a picture is quite low, wouldn't it make sense to choose different values for Red then. Right?

And if the picture is quite dark, wouldn't generally darker RGB colors be better? Right?

The techinque I use is to split the original into three separate layers - red, green, and blue. These layers, when combined - of course - give the original image. So the idea is to display these on the '2600 over consecutive frames with the colour set to red, green, or blue to get the original.

The problem is that instead of (say) 256 intensities of red or green or blue per pixel, the '2600 only allows two (black and red for example). If this were the best we could do, then we'd only be able to display 16 colours (combinations of black, red, green, blue) - which looks pretty horrible.

The trick is to colour-reduce each of the layers to just 2 colours, but using dithering. Dithering gives the visual effect of more intensities. It works beautifully when dithered two-colour images are overlapped - suddenly we have the perception of lots of shades again.

Cheers
A

[ZylonBane]

Which paint program are you using for this? I've been using Paint Shop Pro, using the Stucki error diffusion filter. Floyd-Steinberg seems to create too many on pixels.

And do you split first, then dither down, or dither down, then split? Seems to be a toss-up which way is better. In the sample below, I think the clown came out a little clearer using split-first, but all the "montage" pics earlier in this thread used the palette-loading method.

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[Thomas Jentzsch]

adavie said:

The trick is to colour-reduce each of the layers to just 2 colours, but using dithering.  Dithering gives the visual effect of more intensities.  It works beautifully when dithered two-colour images are overlapped - suddenly we have the perception of lots of shades again.

I'm doing about the same:
- 1. resample down to 48xsomething pixels
- 2. load a RGB-MYC-BW palette (I'm still not convinced that the values in the palette can't be optimized), and select dithering.
- 3. split the image into three channels. The result should consist out of only two very different shades or Grey (Black and White). Normally I get four shades of Grey but two of them are always near White and two are near Black (unless I tweak the palette extremly).
- 4. reduce the colors of ech channel down to 2 colors (B/W), which will give you the pattern for each of the three layers.

BTW: What kind of dithering do you think works best?

[Thomas Jentzsch]

ZylonBane said:

Which paint program are you using for this? I've been using Paint Shop Pro, using the Stucki error diffusion filter. Floyd-Steinberg seems to create too many on pixels.

I'm using a rather old PSP 4.12. Unfortunately I can't select the dithering algorithm when loading a palette.

If you split the channels first, ordered dither might be better, because then the dithered pixels are at the same position.

[Andrew Davie]

ZylonBane said:

Which paint program are you using for this? I've been using Paint Shop Pro, using the Stucki error diffusion filter. Floyd-Steinberg seems to create too many on pixels.

And do you split first, then dither down, or dither down, then split? Seems to be a toss-up which way is better. In the sample below, I think the clown came out a little clearer using split-first, but all the "montage" pics earlier in this thread used the palette-loading method.

Exact process....
1. Load image
2. Optionally enance brightness/contrast
3. Separate into RGB components (there's a menu option) - this gives 3 images, each a grey-shaded image representing the intensity of colour for each.
4. Colour-reduce each of these to 2-colours (B&W) using a dithering technique of your choice. I use floyd-steinberg.
5. Display on '2600


So I split, then dither. I don't play around with palettes at ALL.
I'm using Paint Shop Pro version 6.something

Cheers
A