# resynth

resynthesis is the process of taking a source texture and
creating similar (oft tiling) textures based on it.

resynth is a C rewrite of the original resynthesizer by [Paul Harrison.][pfh]
it does not require GIMP to function; just feed it image paths and it will save copies.
however, this program lacks the patching (masking) and texture transfer abilities of the original plugin.

resynth produces [tiling images like those seen here.][examples]

[pfh]: http://logarithmic.net/pfh/
[examples]: http://logarithmic.net/pfh/resynthesizer/more

## related projects

* [the original resynthesizer GIMP plugin in C++][orig] and [the associated paper][paper]
* [an updated resynthesizer GIMP plugin in C and C++][gimp]
* [syntex: similar algorithms based on resynthesizer in C#][syntex]

[orig]: http://logarithmic.net/pfh/resynthesizer
[paper]: http://www.logarithmic.net/pfh-files/thesis/dissertation.pdf
[gimp]: https://github.com/bootchk/resynthesizer/
[syntex]: https://github.com/mxgmn/SynTex/

## help

```
usage:
  -a  --autism
        sensitivity to outliers
        range: [0,256];     default: 32
  -N  --neighbors
        points to use when sampling
        range: [0,1024];    default: 29
  -r  --radius
        square neighborhood, always odd
        range: [0,32];      default: [n/a]
  -R  --circle-radius
        circle neighborhood radius
        range: [1,128];     default: [n/a]
  -M  --tries
        random points added to candidates
        range: [0,65536];   default: 192
  -p  --polish
        extra iterations
        range: [0,9];       default: 0
  -m  --magic
        magic constant, affects iterations
        range: [0,255];     default: 192
  -s  --scale
        output size multiplier; negative values set width and height
        range: [-8192,32];  default: 1
  -S  --seed
        initial RNG value
                            default: 0 [time(0)]
  {files...}
        image files to open, resynthesize, and save as {filename}.resynth.png
        required            default: [none]
```

the `radius` and `polish` parameters should probably be
properly described or removed.

### neighborhood

offsets are sorted in ascending distance from the center (the 0,0 point).

the order of equal distances is undefined.
this probably doesn't matter matter,
considering the algorithm handles non-circular
neighborhoods just fine — more on that later.

consider the first 29 offsets,
which is the default number of neighbors:

* distance of 0:  
    `{ 0, 0}`
* distance of 1:  
    `{ 0,-1}, {+1, 0}, {-1, 0}, { 0,+1}`
* distance of sqrt(2):  
    `{-1,-1}, {-1,+1}, {+1,+1}, {+1,-1}`
* distance of 2:  
    `{+2, 0}, {-2, 0}, { 0,+2}, { 0,-2}`
* distance of sqrt(5):  
    `{-1,-2}, {-2,+1}, {-2,-1}, {+1,+2}, {-1,+2}, {+2,-1}, {+1,-2}, {+2,+1}`
* distance of sqrt(8):  
    `{+2,-2}, {-2,-2}, {-2,+2}, {+2,+2}`
* distance of 3:  
    `{+3, 0}, { 0,-3}, {-3, 0}, { 0,+3}`

the default neighborhood of 29 yields a (pixelated) circle,
as in this crude ascii art:
```
   X
 XXXXX
 XXXXX
XXXXXXX
 XXXXX
 XXXXX
   X
```

resynth provides a portion of [the associated integer sequence A057961,][A057961]
allowing the neighborhood to be specified as a radius-like size,
with guaranteed symmetry about the X and Y axes.
this is the `-R` flag, and the first few values are visualized here:
```
   -R1     -R2     -R3     -R4     -R5     -R6     -R7

                                                    X
                            X      XXX    XXXXX   XXXXX
            X      XXX     XXX    XXXXX   XXXXX   XXXXX
    X      XXX     XXX    XXXXX   XXXXX   XXXXX  XXXXXXX
            X      XXX     XXX    XXXXX   XXXXX   XXXXX
                            X      XXX    XXXXX   XXXXX
                                                    X
                      equivalent to
   -N1     -N5     -N9     -N13    -N21    -N25    -N29
```
[A057961]: http://oeis.org/A057961

## notes

includes header libraries from [nothings (stb)][stb] and [notwa (kyaa).][kyaa]

[stb]: https://github.com/nothings/stb
[kyaa]: https://gist.github.com/notwa/5d287d807ffe11bbb553462c9940445c#file-kyaa-md

compile like
```
clang -std=gnu11 -lm -Ofast resynth.c -o resynth
```

extra flags that i use are
```
-Wall -Wextra -Werror=implicit-function-declaration -Winline -Wshadow
-Wno-unused -Wno-padded -Wno-missing-field-initializers -Wno-misleading-indentation -Wno-disabled-macro-expansion -Wno-language-extension-token -Wno-unknown-warning-option
```