kris
5cab854269
Fit palettes from overlapping line ranges, and map line to palette
...
when dithering with two limitations:
- cannot choose the same palette as the previous line (this avoids banding)
- must be within +/- 1 of the "base" palette for the line number
This gives pretty good results!
2021-11-11 16:10:03 +00:00
kris
ee2229d0ea
* Modify Floyd-Steinberg dithering to diffuse less error in the y
...
direction. Otherwise, errors can accumulate in an RGB channel if
there are no palette colours with an extremal value, and then when
we introduce a new palette the error all suddenly discharges in a
spurious horizontal line. This now gives quite good results!
* Switch to using L1-norm for k-means, per suggestion of Lucas
Scharenbroich: "A k-medians effectively uses an L1 distance metric
instead of L2 for k-means. Using a squared distance metric causes
the fit to "fall off" too quickly and allows too many of the k
centroids to cluster around areas of high density, which results in
many similar colors being selected. A linear cost function forces
the centroids to spread out since the error influence has a broader
range."
2021-11-11 11:10:22 +00:00
kris
8c34d87216
WIP - interleave 3 successive palettes for each contiguous row range.
...
Avoids the banding but not clear if it's overall better
Also implement my own k-means clustering which is able to keep some
centroids fixed, e.g. to be able to retain some fixed palette entries
while swapping out others. I was hoping this would improve colour
blending across neighbouring palettes but it's also not clear if it
does.
2021-11-10 18:30:39 +00:00
kris
322123522c
Assign scan lines randomly to palettes and cluster independently. This doesn't give good results either, since
...
neighbouring lines end up getting similar but not identical colours, which still results in horizontal striping.
2021-11-10 00:34:17 +00:00
kris
fb52815412
Experiment with striping 16 palettes contiguously across line ranges.
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As expected it has clear banding. A better approach (though still not optimal)
might be to assign lines to palettes randomly.
2021-11-09 22:42:27 +00:00
kris
80885aabf9
Working SHR version. Still just uses a single palette
2021-11-09 22:26:34 +00:00
kris
21058084e2
Tidy
2021-11-09 16:14:37 +00:00
kris
01b19a4a06
Use 4-bit RGB values instead of 8-bit
2021-11-09 15:35:44 +00:00
kris
a92c9cd7b5
Work in CAM16-UCS colour space and cythonize
2021-11-09 15:13:07 +00:00
kris
173c283369
First implementation of using k-means clustering in RGB space to dither a 320x200 SHR image.
2021-11-09 11:23:25 +00:00
kris
0630db2bf1
More relnotes
2021-11-04 14:55:23 +00:00
kris
f097945b2e
Add version history
2021-11-04 14:46:53 +00:00
kris
aebb21263e
Update docs
2021-11-04 14:35:14 +00:00
kris
387500a9b4
Remove stray file
2021-11-04 14:34:44 +00:00
kris
bd19d27bd3
Add a script to regenerate image conversions for example images, and add a .po disk image
2021-11-04 14:32:58 +00:00
kris
7e68847bfe
nit
2021-11-04 14:31:33 +00:00
kris
1010b64272
Fix shift_pixel_window when shift_right_by > window_width
2021-11-03 15:19:29 +00:00
kris
34ae40ac2d
Fix a bug with output for non-ntsc palette
2021-11-03 15:17:57 +00:00
kris
b7174778e6
Oops, no that was wrong. I forgot to cross-check against OpenEmulator <o>
2021-11-03 12:40:22 +00:00
kris
bf76271d75
NTSC conversion should be using YIQ space instead of YUV, which seems
...
to explain several fudge factors I needed to include to match colours.
2021-11-02 23:28:58 +00:00
kris
df0adec8aa
Fix typo
2021-11-02 22:24:47 +00:00
kris
d35cdbc877
Switch remaining palettes to be indexed by (n-bit pixel value, NTSC
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phase) and update the comments to explain the encoding scheme.
2021-11-02 22:15:13 +00:00
kris
52bd35e875
Update comment
2021-11-02 22:15:09 +00:00
kris
3544bd74c8
Update comment
2021-11-02 22:14:59 +00:00
kris
1ed565ff8d
Fix a bug with palette depths < 8
2021-11-02 22:14:42 +00:00
kris
0f1ec6f6f2
Optimize memory a bit
2021-11-02 21:25:00 +00:00
kris
4fbb0faf84
Fixes
2021-11-02 15:47:37 +00:00
kris
9dbf413733
Tidy
2021-11-02 15:45:20 +00:00
kris
e84dfb59f9
Tidy a bit
2021-11-02 15:26:43 +00:00
kris
b63fd81c07
Unify DHGRScreen implementations
2021-11-02 15:23:23 +00:00
kris
75a3c6bc48
Simplify image_to_rgb and remove the need for DOTS and DOTS_TO_INDEX
2021-11-02 15:14:22 +00:00
kris
809b975e6e
Return a bitmap directly from dither_image. This removes the need to
...
deal with n-bit encodings at all in DHGRScreen
2021-11-02 14:42:00 +00:00
kris
b7e8c69f64
More descriptive variables
2021-11-02 13:48:53 +00:00
kris
cf69dc9cf2
Bounds check lookahead
2021-11-02 13:42:23 +00:00
kris
8cfee55b1d
Get rid of support for 140px mode, it was only useful as a demo of why
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other converters have the wrong basic approach.
2021-11-02 13:40:32 +00:00
kris
d442baf1f1
Tidy a bit
2021-11-02 12:30:43 +00:00
kris
5675fac40d
Clean up a bit and accommodate palette depth in sliding pixel window
2021-11-02 12:29:30 +00:00
kris
24644658cb
Tidy a bit
2021-11-01 12:10:02 +00:00
kris
0c588f7489
Tidy
2021-07-19 18:40:16 +01:00
kris
e5c49b3518
Floyd-Steinberg is working well now, and gives better detail
2021-07-19 18:39:38 +01:00
kris
feefdb5dc6
Use .npy format for RGB to CAM16UCS conversion matrix, and get rid of precomputed CIE2000 distances
2021-07-19 18:35:44 +01:00
kris
e979df03bc
Nope, don't need XYZ
2021-07-19 18:13:43 +01:00
kris
8b500b16cb
Dither in XYZ representation but use CAM16UCS for colour differences.
...
This gives the best of both worlds: dithering in a linear space, with
good (and fast) perceptual error differences
TBD: would linear RGB work as well as XYZ?
2021-07-19 17:54:46 +01:00
kris
4984df7f7a
Tidy up and optimize a bit
2021-07-19 13:21:32 +01:00
kris
e08f25e4cc
Simplify
2021-07-19 12:55:50 +01:00
kris
20a73ffb8a
Checkpoint - working again, and simpler
2021-07-19 12:33:49 +01:00
kris
508ce134aa
Try to fix how we compute the next pixel palette for 8-bit mode.
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Still not sure this is correct.
2021-07-19 09:58:22 +01:00
kris
70074a2942
Support arbitrary gamma correction of input image
2021-07-19 09:57:26 +01:00
kris
7a3adea025
Try cam16UCS instead
2021-07-15 14:25:32 +01:00
kris
4fcda908bd
WIP - use colourspacious to perform image dithering in CAM02_UCS
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colour space, which is supposed to be perceptually uniform. i.e. we
can use Euclidean distance instead of CIEDE2000
2021-07-15 13:58:22 +01:00
