Real GBA and DS-Phat colors


#161

I made a conversion list for developers who are implementing color correction to their software. This is specifically about how the GBA-Color shaders or Color-Mangler shader performs. Most of the color shaders are based on Color-Mangler shader.

The top one shows how it’s converted correctly. The conversion is explained.

Color-Mangler has multiple conversions.

First, it changes the gamma to 2.2 on the image, so it is darker. It is from Target_Gamma command that darkens it.

Then, we have the color values, RGB ones, luminance, saturation, and contrast applied before reversing the gamma on the next step. It is set on a dark image from the first step.

Finally, we have Display_Gamma command that does the gamma conversion on the processed image. It does reverse the gamma, so it does divide 1 with whatever the number it is set on Display_Gamma, like 2.2. (1/2.2) = 0.4545…

This is a similar process that the .icc profiles do on applications to have correct brightness on the colors with color correction on the image. As you can see on the final image, the color primaries have better luma levels. As you can see on the final and right image, that’s how the GBA looks when I used the actual hardware.

So here are the wrong process ones:

  1. On the middle of the photo, it only does color correction with the same RGB values from the shaders above, but without gamma conversion involved. It is the same effect if you set both Target_Gamma and Display_Gamma to 1.0 to not have any gamma conversion.

It causes darker colors overall, and it is more noticable on the primary colors such as pure red, green, and blue. I’ve seen this conversion on apps like Gambatte and Sameboy where the converted colors are darker on colors. The latter has darker greens and yellows, making them more noticably dark. The Zelda image may not look as dark, but that’s because the colors on those snapshots are not originally showing pure RGB colors.

  1. For color conversion, if you want to bring the primary colors to have the exact colors from the correct solution without using gamma conversion, you would have to put different values on each color values to have it exactly on the primary colors only.

However, because of that, along with the lack of gamma conversion, it causes unstable image. It looks too bright that clips through. Also, the greyscale are not grey at all, so colors are all over the place. This is even worse solution overall.

I know by doing color conversion with gamma involved, the color primaries change because it is supposed to look darker on the process in order to look great on the image overall. The gamma conversion is needed to retain both luminance and saturation from the original display to emulate well. .icc profiles does this approach since most displays only have gamma at 2.2, so it is needed.

More info about Color Conversion:

http://www.libpng.org/pub/png/book/chapter10.html


#162

@Pokefan531 Amazing work. The gbc_color shader is incredible. With the right combination of shader passes, like a good LCD grid and a console border, I think it allows for the definitive way to play all GBC games with the best of all worlds, to the point that I probably will never want to go back to any of the real consoles again (I can live without the nostalgic golden sheen of the GBC screen).

For the GBA, however, I am wondering if there could be a better approach, or a more balanced “set and forget” sort of color correction.

What I mean is that the gba_color shader works wonderfully for those obvious cases where the game designers overshot the colors expecting hardware compensation, such as the well known cases of Golden Sun, Wario Land 4, and Castlevania HoD (when I played this game on a backlit GBA I thought Konami was trying to go for really psychedelic colors!). The most general trend seems to be that when designers were aiming for earthy/brown colors (or light blues) the raw colors display a garish yellow (or purple).

But in testing a bunch of games for the past few days I’m noticing that a lot of what “should” be the right colors actually show with the raw colors of a backlit GBA/DS, and the gba_color shader distorts them. I base this “should” on colors used in official artwork, other games in the pertinent series, or colors used on the console from which the game was ported (usually the SNES). The general trend I see here is that, post correction, reds that “should” be a vibrant red become more of a ruby color, what “should” be blue shifts toward cyan, green shifts to teal. Also, in particular, it looks like skin tones are negatively affected, making them too red. Oh, the Capcom logo is another example.

Consider, for example, the Phoenix Wright games, the Metroid games, A Link to the Past, and even Super Mario Bros. Advance 2. Phoenix Wright’s canonical skin tone and blue suit color are distorted post correction, but look correct on backlit consoles. Samus’ yellow suit in Zero Mission as well as her fusion suit appear more accurately when played on a backlit GBA/NDS. The colors in ALttP look almost identical to the SNES colors with the aforementioned consoles (when the lowest brightness setting is used in-game), but very different with the correction shader. Super Mario Bros. Advance 2’s problem actually seems to be simply one of gamma (funnily, this game looks SNES-correct on a DS Lite when the screen is turned downwards about 10 degrees thanks to the inferior viewing angles of this TN screen!).

Even an early DS game like Super Mario 64 DS exemplifies this idea. The colors do look on the garish side when raw/on a backlit console, but they are in fact closer to the original N64 colors than with the nds_color correction shader.

Overall, I am left with the sense that the GBA (and possibly NDS) color shaders are more suitable for a minority of cases rather than for most. Perhaps I’m too greedy in hoping for a one-size-fits-all color shader for the GBA, and surely don’t know enough about color conversion to realize how unfeasible it would be, but I’m still wishing that a more general solution is available to help people move away from the real handheld consoles and their disadvantages without having to second-guess the choice of shader frequently.


#163

My shaders got updated few months ago, but it hasn’t been updated on the repo. I did however do a lot of tweaking with how the colors are supposed to look. It is a bit tricky because to see the correct temperature on the screen with different light temperatures, I had to make the 50% grey color from the screen to set the correct temperature on multiple light source. The lights I have kinda made the whites on the screen to try to reach near 6500k. Although, the blue color is supposed to be a bit bright. The hue seems to be like this on the blue primary color.

As for GBC, I’m getting one to see how the colors actually look. It would take a few weeks to examine it. I want to see if the luminance is actually higher than the GBA. Remember, the gbc-color shader started by Monroe who tried to tweak from the gambatte implentation, with gamma correction and hue colors fixed, and I corrected the color temperature. Just to note that both Gambatte and mGBA (maybe VBA-M), the highest green value is 251.

I’ve played around with the LCD-cgwg-V2 shader. I used my phone that has native 1440p resolution and to take snapshot from my PC. I put several sizes and try to have the closest size to GBA-SP AGS-101 (backlit), and LCD-cgwg is pretty similar to how it looked on my GBA SP. The SP subpixel order is BGR instead of RGB. I did change a few settings on the shader presets in the package long time ago to make the lcd shaders be slightly bright, but I decide to leave the gain and the subpixels the default to see better white shades. I would have the black levels at 0, and gamma to 2.2, since most displays are using gamma 2.2.


#164

Are the most updated shaders the one you linked to here (https://drive.google.com/open?id=0B5KxdoFEcyTkZ3I0WWZkM00zT0k) on your August 9 post?

I replaced the files from the repo with these, and for the gba_color shader I can see a clear improvement! Reds and skin tones in particular look much closer to natural now, and overall colors feel more balanced. I would have had no idea, I just assumed that the repo files were the most up to date! Someone should really push the new files into the repo.

I checked out the updated gbc_color also and I can’t tell as much of a difference, but once again it looks fantastic. In a couple of weeks I should have access to my non-backlit GBC, GBA, and DS consoles and will see with more attention how they compare.

I still feel that for a lot of GBA games in particular the raw colors seen in emulators and backlit consoles are what the game designers really wish could be shown, hoping for the best given what the limited GBA screen was able to display. For those colors, the color correction may be a disadvantage. The problem is when they combined those ideal colors with clearly overdone colors with the limitations of the screen in mind, sometimes overwhelmingly. In any case, for those games where they did the latter to an extraordinary extent, I think nothing will beat playing while using these shaders. I’m really glad someone put in all the work needed to make it available to handheld fans.


#165

Yes.

I think they only updated the gbc-color ones, or it may look similar. To compare the screen and the shaders, it is tricky to see the same exact colorspace. A lot of monitors are aimed on the sRGB colorspace, but most of them are just very close to it. Monitors in a lot of cases aren’t calibrated to 6500k as often, but still looks very close. The screens on the NDS are a bit colder like above 6500k. Also, depending on the light source, the gba and gbc screen needs to be lit that is close to the standard color temperature. The best way I found to compare is to play the game on those screens as often. The eyes would adjust the color temperature on the screen. Also, unlike modern screens, the greyscale is not 100% grey or close to the white temperature of the screen, so it looks a bit colder. I had to use the curve tool on Photoshop to get the best results. This method does the best job at replicating the color temperature that your eyes see when it’s already adjusted. It is best to find a light for non-lit screens that is close to the standard temperature to see better. Just to note that those screens often show the rainbowing effect, especially if you use a flashlight on the screen. Commonly on the first party games, early games was adjusted for the screen, and they pre-calibrated the colors for the screen to see the same visual effect.

One last thing. Not sure if Woozle is available, but my last two posts involved how the colors are adjusted by using the gamma correction, or gamma-to-linear method to adjust colors on the primary so some colors don’t look dark, mainly around the primaries. I’ve seen the post for the Gambatte that added my gbc shader, and showed that it is an alternative to gambatte’s color adjustment. I’ve seen GBA HDMI clips and I want to contact him about the gamma correction method.

More info on gamma correction:


#166

It would be great if you could get in touch with Woozle. He already has implemented color correcting shaders and gamma settings on his GBA consolizer, but shaders on his consolizer and on the Retroarch side stand to gain from some comparison and collaboration. You could try reaching out to him through this twitter account: https://twitter.com/Woozle64