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

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

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

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.

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.

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?

Feel free

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 ;)

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

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.

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.


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.

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

Nice to hear, definitely will use your program for something in the future!

Wow, that was fast, thanks!

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.

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

Amazing results!

Thank you!

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

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

@Hyllian: Why wouldn't you be using libpng?

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.

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

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

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

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