Hyllian

Yes, great job! That old "if" is my implementation for sharp 90 degree edges, similar to yours. The new version is a bit soft in that restriction, so that only some sharp edges are left intact. I like the new way more because it doesn't cause those nasty artifacts I pointed earlier. You could use the three ways (rounded, sharp and sharpest) in your software.

Those proportions are right. I can confirm this.

I'm afraid you wouldn't understand. The sources are a real mess. There's many unuseful or only test code. That's my code playground . Anyway, you can get here

I don't see a problem with your 3x noblend implementation. The only difference is that you do not change pixels when sharp edges are found. It's not an issue. It's just another way to solve the problem. But, I think you should investigate those AlphaBlend functions to see why they perform slightly different than mine.

I zoomed that cross from 4xBR pic comparison you made earlier. See how these pixels are different: Yours: Mine: As you can see, there's some discrepancies. The result is because your AlphaBlend functions are not exactly like mine.

For me, the differences are in the implementation of AlphaBlend functions. Your implementation is identifying correctly the pixels which need interpolation. But, then, when it uses its AlphaBlend functions to interpolate, some discrepancies appear.

No, I mean 4x. If you zoom it using nearest neighbor, you'll see that pixel values in the cross contours have different rgb values. I use GraphicsGale to analyze pixel values. (Only four pixels have different values.) Ok, I'll get that sonic pic and add to my collection. So you're from Berlin. I vIsited it in 2008. Loved it!

What Sonic image is that? I have lots of test images here, majority of them are pixel arts I got from pixeljoint. Ah, I'm from Brazil.

I don't know yet. But it seems the glitch in 2x is affecting 4x version too, though not easily noticeable. Look at the cross (right down side) in that 4X comparison you posted earlier, the contour is a bit different. Probably some of those alphablend function implementations differ from mine.

Yes, the same artifacts are there. Look at the Yoshi's Belly, there's a square block appended. Yoshi's Nose has a square block too. My 90º sharp version presents those too. They're minor artifacts, though. This image is my test sample. If you try using any other algorithm in your software, you'll see none comes close to xBR in accuracy.

Done. Look again at the image.

I have an implementation that renders sharper 90º too, but it causes some small artifacts in some pictures. I'm curious to see if yours don't cause them. Can you scale this image using your 3x version and post here? EDIT: Sorry, I posted the wrong image. Now it's corrected and it's a png lossless image.

I'm seeing you've changed the "eq" and "df" functions. Where's the implementation of "IsLike" and "IsNotLike"? I'm afraid you're using a "hard decision implementation" instead a soft one.

Haha. The noblend only works well when you choose an odd scale factor (3x, 5x, 7x, ...). That's why those 2x and 4x noblend pictures you posted aren't good (they have some bad artifacts, jaggies). Anyways, you did a great job! I specially liked the 3x reversed version more than mine. I'm looking at the 2X issue, that's the only difference from your implementation I didn't have time to figure out yet.

Thanks for the pics. I'll look into the codes and see if I figure out what's different. Anyways, that 3xBR I think I already know, because I have two implementations for it (one that blends colors and other that don't).