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Hyllian
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Quote Hyllian Replybullet Topic: The challenge to upscale pixel art
    Posted: 07 January 2012 at 8:22pm
Yes, this is hard as hell.

I'm trying for almost a year.

Here my upscaler which turn any png image file into a 4x upscaled version:

http://www.multiupload.com/TXUTZFDW2F


just use like this:

4xBR <original_image.png> <upscaled_image.png>


I know this may be an heresy for you, but sometimes it can help someway.

I'm continuing researching about how to perfect this transformation.

Hope you enjoy!

I don't know if I can post pixel arts from pixeljoint upscaled here, so I won't until a confirmation.

Please, do not kill me!
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Quote tanuki Replybullet Posted: 07 January 2012 at 10:51pm
It's better to post images to something like photobucket and link to them here with the button above the comment box that has a little tree on it. Just so we can see what you mean without having to download something, which I'm not going to do. :)

Anyways, to upscale something using a program like photoshop all you have to do is click the image menu, select image size... and then enter a height/width that is an exact multiple of whatever it currently is. Make sure that you select nearest neighbor (preserve hard edges) from the menu within that window so it won't apply any automatic blending.

So for example if you have a 50x100 image then you could make it be things like 100x200, 150x300, 500x1000, etc., as long as it's an exact multiple of your original size.

I don't know how to do it in other programs, but it's probably something similar to this.



Edited by tanuki - 07 January 2012 at 10:54pm
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Quote surt Replybullet Posted: 08 January 2012 at 2:35am
Why on earth would you go to the trouble of writing a program to perform a task that is trivial to do in just about every graphic editor ever made?

Even if you are batch processing I'm sure you can do that with existing commandline tools such as ImageMagick.
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Quote Hyllian Replybullet Posted: 08 January 2012 at 3:22am
Ok, let's begin this so that you understand what I mean.

I don't like nearest neighbor, because it gives a checkerboard feel. And I don't like bilinear filtering, because it blur too much. So I made this program to preserv sharpness and get rid of jaggies.

Here's an example from here (I've got a random pixel art from pj) where I used my program:



Nearest Neighbor:


Smooth upscaling using Gale:


4x with my program:



Edited by Hyllian - 08 January 2012 at 3:31am
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Quote jeremy Replybullet Posted: 08 January 2012 at 3:43am
I understood what you meant :p

I recall something(s) similar over at Pixelation, it's an interesting exercise. The effect of this one is really quite painterly, especially at 2x rather than 4x (i.e. reducing your resampled one).

I wonder how it would take work less perfectly smooth than Panda's, like this

or this
edit:
a couple of similar things from Pixelation

edit edit: what about dither?



Edited by Jeremy - 08 January 2012 at 3:47am
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Quote Hyllian Replybullet Posted: 08 January 2012 at 3:54am
That mutant picture has transparencies. Sorry, my program doesn't support it, so it's out of question.

That ss2011, though, can be processed. I get this (just link to not break the thread size):

http://i.imgur.com/H83j5.png
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Quote jeremy Replybullet Posted: 08 January 2012 at 4:01am
Thanks, that's awesome :O especially for the wispy bits.


^ not transparent


Edited by Jeremy - 08 January 2012 at 4:01am
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Quote Hyllian Replybullet Posted: 08 January 2012 at 4:08am



There are at least two purposes for me to make an algorithm for this task:

1- Print
2- Play classic videogames in high definition TVs.
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Quote moogleymog Replybullet Posted: 08 January 2012 at 5:56am
That's really impressive! :D
I wonder what animated objects would look like. Can you only save as PNG? I did download the program but it won't open for me.
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Quote Hyllian Replybullet Posted: 08 January 2012 at 6:00am
Originally posted by moogleymog

That's really impressive! :D
I wonder what animated objects would look like. Can you only save as PNG? I did download the program but it won't open for me.


This is a command line program. To use:

Open a DOS-Prompt (command line window).

You have to go through the command line to the folder where the program is located. Then use this command:

4xBR <input png> <output png>


If you don't know how to use DOS commands, I'm sorry.
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Quote Hyllian Replybullet Posted: 08 January 2012 at 6:19am
One more example:

Original:


Nearest Neighbor:


Smooth resample from Graphics Gale software:


My algorithm (4xBR):

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Quote DawnBringer Replybullet Posted: 08 January 2012 at 6:39am
Hmm, this is really interesting. Your results looks like a succesful hybrid between the Scale2x/Scale4x and the Kopf/Lischinski spline algorithms (not that I think those could be combined for real). I'd love to hear more about your algorithm if you care to share. Is it locked to x4 or can it handle any sizes?
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Quote Hyllian Replybullet Posted: 08 January 2012 at 6:49am
Originally posted by DawnBringer

Hmm, this is really interesting. Your results looks like a succesful hybrid between the Scale2x/Scale4x and the Kopf/Lischinski spline algorithms (not that I think those could be combined for real). I'd love to hear more about your algorithm if you care to share. Is it locked to x4 or can it handle any sizes?


That standalone app only scale by 4 and use it on my research. But I've made some filters for some emulators that work scaling by 2x, 3x, 4x and even 5x. I don't know if I can post a link to another forum where I present some explanations about the algorithm.



Edited by Hyllian - 08 January 2012 at 6:50am
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Quote jeremy Replybullet Posted: 08 January 2012 at 6:57am
Originally posted by Hyllian

I don't know if I can post a link to another forum


Feel free
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Hyllian
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Quote Hyllian Replybullet Posted: 08 January 2012 at 7:04am
Originally posted by Jeremy


Feel free

Ok. Here the link: http://board.byuu.org/viewtopic.php?f=10&t=2248

That forum isn't about pixel art, though.
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Quote Trick17 Replybullet Posted: 09 January 2012 at 6:58pm
Nice algorithm, looks like a better version of Hqx to me, but some problems are still the same. However, I will memorize your algorithm for me ;)
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Quote Hyllian Replybullet Posted: 12 January 2012 at 9:25am
Originally posted by Super17

Nice algorithm, looks like a better version of Hqx to me, but some problems are still the same. However, I will memorize your algorithm for me ;)

Hi. I'd like to know about these problems you mentioned, so that I could think about how to fix them in some way. Could you elaborate them?
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Quote Hyllian Replybullet Posted: 13 January 2012 at 3:24am
Here the xBR app, now scales to 3x and 4x: http://www.multiupload.com/2JY2QM1AC3

            Usage: xBR <input png> <output png> [<scale_factor>]
            scale_factor: 3x or 4x. (default: 4x)


The 3x implementation is a bit different than the 4x. In 3x I didn't blend pixels, so the original palette is preserved, though the result is bit more jagged. Because of this, 3x scales very well to 9x, 27x and so on.

Here an example:

Original


3x


9x



If you zoom these 3x multiples you'll see that the colors remain original.


Edited by Hyllian - 13 January 2012 at 3:32am
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Quote Hyllian Replybullet Posted: 13 January 2012 at 8:36am
Click to see the real size:
1x.......3x.............................9x..................................27x................................81x
   


3x (no blending, original palette)



Edited by Hyllian - 13 January 2012 at 9:10am
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Quote Trick17 Replybullet Posted: 13 January 2012 at 10:10am

I ment this areas, Hqx has the same problem. Would be outstanding if you could fix that.

And I tried to run your little program, but it doesn't work, always shutting down automatically after I start it... Had the same problem with a Hqx programm, do I need something for this? (Had read about framework or something like that...) Have Windows Vista OS.
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Quote Hyllian Replybullet Posted: 13 January 2012 at 10:27am
Originally posted by Super17


I ment this areas, Hqx has the same problem. Would be outstanding if you could fix that.


This "stair effect" is impossible to solve in realtime. This occurs because when processing a single pixel, the algorithm only can see some of its neighbors, so it can't predict if a line will continue its trajectory or turn to the other way ahead. The only way to solve this is if you can look at the whole picture before processing each pixel, and this is impossible in realtime today. On top of that, the amount of processing would be insane.

Originally posted by Super17


And I tried to run your little program, but it doesn't work, always shutting down automatically after I start it... Had the same problem with a Hqx programm, do I need something for this? (Had read about framework or something like that...) Have Windows Vista OS.


You need to use DOS-Prompt. This is a command line app.
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Quote Trick17 Replybullet Posted: 13 January 2012 at 11:42am
Originally posted by Hyllian

This "stair effect" is impossible to solve in realtime. This occurs because when processing a single pixel, the algorithm only can see some of its neighbors, so it can't predict if a line will continue its trajectory or turn to the other way ahead. The only way to solve this is if you can look at the whole picture before processing each pixel, and this is impossible in realtime today. On top of that, the amount of processing would be insane.
Hm, I was expecting something like that, but would it possible to write a program that could do this? I wouldn't care if it's not in realtime.


Originally posted by Hyllian

You need to use DOS-Prompt. This is a command line app.
Thanks, I tried it, seems to work and it says: "done." But nothing happens. Where do I find my new image? Also, I recive an error message after that: "programm isn't working anymore" But nothing happens too.
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Quote Hyllian Replybullet Posted: 13 January 2012 at 12:13pm
Originally posted by Super17

Hm, I was expecting something like that, but would it possible to write a program that could do this? I wouldn't care if it's not in realtime.

Too complex to make. I have other priorities for now (for example, implement some kind of cache to speed up processing).

Originally posted by Super17


Thanks, I tried it, seems to work and it says: "done." But nothing happens. Where do I find my new image? Also, I recive an error message after that: "programm isn't working anymore" But nothing happens too.

It seems you never used DOS. Put the program and the image.png in the same folder. From the command line go to that folder (you need to navigate through DOS commands). Then, use the command to use xBR. You have to know where you're creating the new image.png 3x scaled.
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Quote Trick17 Replybullet Posted: 13 January 2012 at 12:48pm
Well, that's exactly what I did, I just didn't change the folder, because DOS could find the program and I thought it will work. I'm not new to DOS, but still a raw bignner.
It's working now, thanks for patience

Question: Is it possible to have the option for 2x scaling as well?


Edited by Super17 - 13 January 2012 at 12:49pm
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Quote Hyllian Replybullet Posted: 13 January 2012 at 12:55pm
Originally posted by Super17


Is it possible to have the option for 2x scaling as well?

Yes. I'll insert it later.
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Quote Trick17 Replybullet Posted: 13 January 2012 at 1:02pm
Originally posted by Hyllian

Yes. I'll insert it later.
Nice to hear, definitely will use your program for something in the future!
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Quote Hyllian Replybullet Posted: 13 January 2012 at 2:01pm
2x done!

http://www.multiupload.com/GQFZDT9MAV

            Usage: xBR <input png> <output png> [<scale_factor>]
            scale_factor: 2x or 3x or 4x. (default: 4x)


2x (your avatar)



Edited by Hyllian - 13 January 2012 at 2:01pm
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Quote Trick17 Replybullet Posted: 13 January 2012 at 4:07pm
Wow, that was fast, thanks!
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Quote Hyllian Replybullet Posted: 05 December 2012 at 4:41am
Ive improved a bit the algorithm for pixel arts that use many colors. It preserves dithering. It only scales by2, though.


Download here:  https://anonfiles.com/file/92e2ed25e7efaae5fe28f76608658be8


Example of this thread (click to see in full size):]
http://bildr.no/view/1335316

Usage:

          Usage: 2xBRh <input png> <output png>



Original


2x Scaled



More screenshots here: http://imgur.com/a/XAwx5


Edited by Hyllian - 05 December 2012 at 2:14pm
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Quote Mr.Fahrenheit Replybullet Posted: 13 December 2012 at 3:24pm
I was thinking when I saw how nice the pictures looked with anti-aliasing. Maybe, if possible, you could have the image render with anti-aliasing but not introduce new colors so it uses colors form before to make aa.
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Quote cybrasty Replybullet Posted: 18 December 2012 at 7:51am
Hey Hyllian - can you reupload the 3x scaler program? The links gives me internet vs holywood pettition and no download option.
Thanks for a great job!
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Quote neota Replybullet Posted: 18 December 2012 at 3:19pm
Originally posted by Super17

Hm, I was expecting something like that, but would it possible to write a program that could do this? I wouldn't care if it's not in realtime.


Where that'll ultimately end up is something like Inkscape's Trace Bitmap command. If you are looking for a base to build a 2x or 3x version on, consider trying Trace Bitmap on the output of Hyllian's program. You'll need to select 'Multiple scans->Color' and set max number of colors about right; turn off Smooth and make sure Stack Scans is on. Also in the Options tab disable 'Suppress Speckles' and reduce the 'Smooth corners' setting to something like 0.6.
Here's an example output, generated from Hyllian's 3x image because pixel art has typically too-small details for the design assumptions of PoTrace (the backend system of Trace Bitmap):
Note it has antialiasing. You can turn antialiasing off in your SVG renderer if you want no new colors added.

Rendering at 1x (this is like the original with extra antialiasing):


2x:


3x:


6x:
Link only, cause inlining such a huge image would be obnoxious. http://i.imgur.com/uduWP.png (the linking setup on this board is freaking out, so I couldn't make that into a clickable link.)


Edited by neota - 18 December 2012 at 3:22pm
absolutely.
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Quote Hyllian Replybullet Posted: 19 December 2012 at 3:30am
Originally posted by cybrasty

Hey Hyllian - can you reupload the 3x scaler program? The links gives me internet vs holywood pettition and no download option.
Thanks for a great job!


Sure!

It's here:  https://anonfiles.com/file/f25320e84e03808903c48a30b77c2f6a


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Quote Hyllian Replybullet Posted: 19 December 2012 at 3:33am
Originally posted by neota



Where that'll ultimately end up is something like Inkscape's Trace Bitmap command. If you are looking for a base to build a 2x or 3x version on, consider trying Trace Bitmap on the output of Hyllian's program. You'll need to select 'Multiple scans->Color' and set max number of colors about right; turn off Smooth and make sure Stack Scans is on. Also in the Options tab disable 'Suppress Speckles' and reduce the 'Smooth corners' setting to something like 0.6.
Here's an example output, generated from Hyllian's 3x image because pixel art has typically too-small details for the design assumptions of PoTrace (the backend system of Trace Bitmap):
Note it has antialiasing. You can turn antialiasing off in your SVG renderer if you want no new colors added.


Amazing results!

Thank you!
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Quote Hyllian Replybullet Posted: 14 September 2013 at 3:22pm
Hi, long time no see!

The development continue and I have some news. I've already got xBR LV4.

Here's a new executable only for 4x:
http://https://anonfiles.com/file/95553996f5223220944d8d258202c13e

A result for comparison:




Edited by Hyllian - 14 September 2013 at 3:24pm
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Quote neota Replybullet Posted: 14 September 2013 at 5:39pm
Your url is incorrect -- This is the correct url : https://anonfiles.com/file/95553996f5223220944d8d258202c13e
Your existing one ended up redirecting to homeimprovement.com


Aside from that, the example image looks good and I am glad to see there is some way for me to test LV4 :)

Seems to work well even on sprites with high numbers of colors:

Source image:


Scaled (in 2 parts because of size)



Tomato and capsicum are notably the hardest cases here (30+ colors each), and it copes well with them, particularly getting a clean edge around the object despite variation in color along the edge.
Also translates the carefully layered dithered areas on the cumquat into halftoning very accurately, producing a harmonious result.


Is a non-AA version coming? (Non-AAed scaling -> better quality vectorization when brought into Inkscape)

EDIT:
On the subject of animation, I grabbed orkimides' Mario animation
and tried scaling that. It's fairly consistent and doesn't jump around. There seem to be issues with the alpha channel though (see dancing black pixels and added 'selout' around edges.). The obvious fix for that is to store the original mask as B/W, dilate the 'solid pixels' into transparent areas a few times (it can be increased a few more times if you ever get to LV5/LV6), scale *that*, scale the mask, and finally, apply the mask to the main result.

Original:


Scaled:





Edited by neota - 14 September 2013 at 6:47pm
absolutely.
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Quote Hyllian Replybullet Posted: 14 September 2013 at 7:32pm
Tks for the examples.

It doesn't support alpha channel, indeed. I won't bother with it yet, because I prefer to use the time to evolute the main algorithm.


Edited by Hyllian - 14 September 2013 at 7:32pm
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Quote neota Replybullet Posted: 14 September 2013 at 8:00pm
BTW after trying it on some larger images I found it refuses large images (>500000 input pixels). Why is this? Even a 1000000pixels image would only occupy 64mb memory after scaling it up 4x.

Edited by neota - 14 September 2013 at 8:24pm
absolutely.
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Quote Hyllian Replybullet Posted: 15 September 2013 at 2:50am
The internal free lib I used to deal with png files has a bug that it won't work well with big images, so I decided to put that limit to save some wasting processing time.

Edited by Hyllian - 15 September 2013 at 2:53am
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Quote neota Replybullet Posted: 16 September 2013 at 4:24am
@Hyllian: Why wouldn't you be using libpng?
absolutely.
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Quote Hyllian Replybullet Posted: 17 September 2013 at 3:56pm
Too bloated for my test needs...



Edited by Hyllian - 17 September 2013 at 3:56pm
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Quote neota Replybullet Posted: 17 September 2013 at 4:14pm
ls -l /usr/lib/libz.a /usr/lib/libpng.a

-rw-r--r-- 1 root root 326K Jul 20 11:30 /usr/lib/libpng.a
-rw-r--r-- 1 root root 116K Apr 29 23:52 /usr/lib/libz.a

300-400k before linking? I suppose that is big, yeah.
absolutely.
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Quote Hyllian Replybullet Posted: 18 September 2013 at 10:33am
When I said too bloat, I mean it does too much things and I just need to open and save a png file. libpng is too complicated and requires time to understand how to setup it correctly. I won't waste my time with it considering I already have an easy-to-use free png lib implemented in my code.

BTW, I just noticed the free lib (lodepng) I use was updated recently. So I updated my app to use the last lodepng. See if that bug you reported is fixed by trying the updated standalone app below:

https://anonfiles.com/file/3da0a7cf63a8fbd6599be2ddb693ffec


Edited by Hyllian - 18 September 2013 at 10:34am
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Quote neota Replybullet Posted: 18 September 2013 at 11:43pm
THANK YOU!

It certainly is fixed :)


EDIT: BTW, I also found a weird surprise where the output can become indexed rather than 32bit truecolor. Here is the input image, hopefully imgur will not modify it:





Edited by neota - 19 September 2013 at 12:34am
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Quote Hyllian Replybullet Posted: 19 September 2013 at 3:32pm
And here's the 3x NoBlend version:

https://anonfiles.com/file/ca64833f5adb4bd6bb1a9aa6e8ddb62c

Example:

Original



3xBRLV4 NoBlend:

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Quote 2blackbar Replybullet Posted: 19 September 2013 at 4:39pm
now this looks impressive, its interesting , looks kinda like oil painting filter but without blur
Can you modify your program so i could just drag and drop png file onto it and it would save scaled in the same folder ?
Heres bat command for others :
4xBRLV4.exe pic.png  upscpic.png

make new text file save it as bat file and run


Edited by 2blackbar - 19 September 2013 at 4:47pm
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Quote neota Replybullet Posted: 19 September 2013 at 7:12pm
And here's an equivalent shell script for running it under WINE on Linux.

Also supports selecting between scale levels (specify 3 or 4 as the first argument) and will automatically convert non-PNG input files to PNG.



Edited by neota - 19 September 2013 at 9:32pm
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Quote 2blackbar Replybullet Posted: 20 September 2013 at 5:57am
I like how it uspcales lineart, i only have suggestion for creating less rectangle like shape and less circle like shapes from signgle pixel , instead  how about trying it to fade into more spikey shape not so round like  o  and not like this [ ]   but like <> so it doesnt end suddenly with 2 pixels on top and botton but with one pixel, something like this(on left current method) :   but would be best if it could detect if it should be spikey horizontally or vertically and detect if line was horizontal or vertical so line would end more spikey and not so round.


I like the result of 4x upscale and 50% bicubic downscale:

So decent downsize algorithm could fix a lot of stuff too


Edited by 2blackbar - 20 September 2013 at 6:27am
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Quote bzz Replybullet Posted: 11 December 2013 at 8:02am
Wow I'm impressed. I want to implement it in my iPad app someday
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Posts: 104
Quote bluedxca93 Replybullet Posted: 26 December 2013 at 3:21am

Hi,


3xbr lv 3

redrawn by hand


nearest neighbour.

Your algorith does'nt like chess patterns i think. These are often used as
" dithering" in pixel art and theres also the edge "bug".
Your algorithm is good for upscaling  640x480 px fotos  and images over 128x128 px.
It is better than the libdepiselixe kopf algorithm. it is the best i could  find so far, but perhaps you could try to fix the problems with the chess patterns.

Regards bluedxca93



Edited by bluedxca93 - 26 December 2013 at 3:25am
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