What is this fork for?
I did not touch a single line of the algorithm code but I did some modification:
- The original project is a lib, this is lib and a command line application that uses it
- The packages names are now coherent
- This is a maven project, not an Eclipse project
hqx ("hq" stands for "high quality" and "x" stands for magnification) is one of the pixel art scaling algorithms developed by Maxim Stepin, used in emulators such as Nestopia, bsnes, ZSNES, Snes9x, FCE Ultra and many more. There are 3 hqx filters: hq2x, hq3x, and hq4x, which magnify by factor of 2, 3, and 4 respectively.
Like the hqxSharp project, the focus of this code is asset creation and usage in tools, so no optimizations were done, just an almost-direct copy of the code.
Darshan@Darshan-HP:/Codice/Java/hqx-java/target$ java -jar .\hqx-java.jar hqx image converter Usage -> hqx.jar [options] inputFile the input file can olso be specified with an option If not overridden output file name will be inputfile.hq2x.png of hq2x hq3x.png for hq3x and so on Option Description ------ ----------- -?, -h, --help show help --all Upscale the input file with hq2x,hq3x,hq4x --hq2x Upscale the input file with hq2x --hq3x Upscale the input file with hq3x --hq4x Upscale the input file with hq4x --input Specify input file --output Override the default naming convention for output file
- Wikipedia entry for hq2x
- Cached version of the original links
A decription from the original implementation
The first step is an analysis of the 3x3 area of the source pixel. At first, we calculate the color difference between the central pixel and its 8 nearest neighbors. Then that difference is compared to a predefined threshold, and these pixels are sorted into two categories: "close" and "distant" colored. There are 8 neighbors, so we are getting 256 possible combinations. For the next step, which is filtering, a lookup table with 256 entries is used, one entry per each combination of close/distant colored neighbors. Each entry describes how to mix the colors of the source pixels from 3x3 area to get interpolated pixels of the filtered image. The present implementation is using YUV color space to calculate color differences, with more tolerance on Y (brightness) component, then on color components U and V. That color space conversion is quite easy to implement if the format of the source image is 16 bit per pixel, using a simple lookup table. It is also possible to calculate the color differences and compare them to a threshold very fast, using MMX instructions. Creating a lookup table was the most difficult part - for each combination the most probable vector representation of the area has to be determined, with the idea of edges between the different colored areas of the image to be preserved, with the edge direction to be as close to a correct one as possible. That vector representation is then rasterised with higher (3x) resolution using anti-aliasing, and the result is stored in the lookup table. The filter was not designed for photographs, but for images with clear sharp edges, like line graphics or cartoon sprites. It was also designed to be fast enough to process 256x256 images in real-time.
This software is released under the GNU Lesser General Public License
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Copyright © 2007 Free Software Foundation, Inc. <http://fsf.org/>
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