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waifu2x is a highly praised image up-scaler which does slightly better job than most other tools and filters when it comes to image up-scaling. The original version is Windows-only and it requires a NVidia GPU. GNU/Linux users can compile and use a fork which uses OpenGL.

A Myriad Of Versions

The original author of waifu2x wrote it for Microsoft Windows with Nvidias proprietary CUDA API as a requirement. That Japanese author, who goes by the GitHub handle nagadomi, describes the original waifu2x as

"Image Super-Resolution for Anime-style art using Deep Convolutional Neural Networks. And it supports photo."

The original waifu2x code has been forked by a whole lot of people who mostly produced other Windows-only versions which were later abandoned. It is therefore hard to find any actually useful code or version which runs on GNU/Linux.


The waifu2x fork waifu2x-glsl, available at https://github.com/yui0/waifu2x-glsl, compiles and runs on GNU/Linux (and Windows and macOS). It uses the cross-platform glfw library to do OpenGL-assisted up-scaling. Its webpage lists these installation instructions for GNU/Linux:

dnf install glfw-devel

Installing the glfx development headers with dnf -y install glfw-devel and cloning the source with git clone https://github.com/yui0/waifu2x-glsl.git and entering the folder with cd waifu2x-glsl and compiling with make was all it took to get a get a working waifu2x_glsl binary. There is no Makefile so there is no make install, that won't work.

Using a compiled waifu2x_glsl requires a "noise model" file. It will by default look for a noise1_model.json file in the current folder. Other files in other locations can be specified by adding a -m path/file.json parameter.

The desired up-scaling size is specified with -s (2 for 2x, 4 for 4x etc) and an output file needs to be specified with -o.

Note that you can not just place waifu2x_glsl and noise1_model.json in $HOME/bin and expect that to work. It looks for a model in the current working folder, not the folder where the binary lives. You can make put both files in $HOME/bin and make an alias:

alias waifu2x="$HOME/bin/waifu2x_glsl -m $HOME/bin/noise1_model.json"

That alias makes it possible to up-scale an image by 4x using

waifu2x -s 4 inputfile.jpg -o outputfile.jpg

The GitHub source includes a folder named vgg_7/art_y/ with four files named "noise1_model.json", "noise2_model.json", "noise3_model.json" and "scale2.0x_model.json". What, if any, difference there is between this files is a unsolved mystery. Testing them with numerous images and comparing the could reveal a difference.

64x64px "agt_family" icon

Everaldo Coelho (www.everaldo.com) is a graphics designer who created several free themes such as "Crystal" and "Kids" in the early 2000s. The Kids theme, released in 2003, did not include any SVG images - only icons up to 64x64. "agt_family.png" is one such icon:

Agt family.png

convert agt_family.png -resize 256 agt_family.256px.ImageMagick.png :

Agt family.256px.ImageMagick.png

waifu2x -s 4 agt_family.png -o agt_family.waifu2x-4x.png:

Agt family.waifu2x-4x.png

waifu2x_glsl appears to lack any PNG transparency support. Adding a white background with GIMP or other software is required to use transparent images. That produces a usable result which can be compared to ImageMagick:

ImageMagick's "convert" waifu2x gimp
Agt family.256px.ImageMagick.png Agt family.waifu2x-4x-2.png Agt family 256 gimp.png

256px photo

Original (though not really, it is a higher-resolution photo down-scaled for testing purposes):








Verdict And Conclusion

The visible difference between up-scaling these images in GIMP and ImageMagick's convert and waifu2x-glsl does not appear to be gigantic. It is hard to make a judgement. Regardless, it is nice that there is a waifu2x implementation which does work on GNU/Linux.

We leave you with the following 500x500 image and three only numbered 2x upscaled images of Jennie from the k-pop group Blackpink for your comparison pleasure and/or consideration:

Based Jennie on relationships.jpg


Based Jennie on relationships-2x-gimp.jpg


Based Jennie on relationships-waifu2x.jpg


Based Jennie on relationships-convert.jpg

Image 1 was made using GIMPs Image ▸ Scale Image, 2 was made with waifu2x and 3 was made using convert -resize.

If you were able to correctly guess which images was made with that tool then waifu2x is probably for you. If you can't tell the difference then it is quite possible that there is no real difference.


Anonymous user #1

6 months ago
Score 0++
Imagemagick certainly did a better job scaling the text. I got #1 correctly as gimp, but other than the text I can't see a difference between #2 and #3.

Anonymous user #2

3 days ago
Score 0++
I checked the results and it seems that the algorithm is not working at all in this case. The results you got are completely wrong and do not represent the algorithm.
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