Crate a_sixel

A-Sixel library for encoding sixel images.

Basic Usage

use a_sixel::BitMergeSixelEncoderBest;
use image::RgbaImage;

let img = RgbaImage::new(100, 100);
println!("{}", <BitMergeSixelEncoderBest>::encode(img));

Choosing an Encoder

• I want good quality:
  • Use BitMergeSixelEncoderBest or KMeansSixelEncoder.
• I’m time constrained:
  • Use BitMergeSixelEncoderLow, or BitSixelEncoder.
• I’m really time constrained and can sacrifice a little quality:
  • Use BitSixelEncoder<NoDither>.

For a more detailed breakdown, here’s the encoders by average speed and quality against the test images (speed figures will vary) at 256 colors with Sierra dithering:

Algorithm	MSE	DSSIM	PHash Distance	Mean ΔE	Max ΔE	ΔE >2.3	ΔE >5.0	Execution Time (ms)
adu	15.07	0.0053	8.66	1.79	12.88	31.6%	4.4%	1416
bit	35.82	0.0132	31.14	3.16	11.03	64.5%	15.1%	426
bit-no-dither	31.78	0.0214	39.10	3.09	10.23	64.0%	13.4%	274
bit-merge-low	10.67	0.0038	13.97	1.95	9.98	32.4%	2.2%	785
bit-merge	10.36	0.0037	13.55	1.89	10.01	31.0%	2.2%	932
bit-merge-better	10.31	0.0037	13.45	1.85	10.21	30.6%	2.2%	1275
bit-merge-best	10.29	0.0037	13.52	1.83	10.26	30.6%	2.2%	1496
focal	14.62	0.0056	19.97	2.30	9.16	45.3%	3.3%	2428
k-means	10.07	0.0036	13.07	1.80	10.17	29.1%	2.2%	2996
k-medians	17.67	0.0068	21.07	2.61	10.17	53.6%	5.1%	7305
median-cut	19.63	0.0059	16.45	2.24	10.36	42.2%	5.9%	692
octree	54.48	0.0148	26.03	3.89	12.49	78.6%	25.4%	682
wu	17.89	0.0068	21.03	2.34	10.24	46.3%	5.1%	1853

Note: Execution time includes the time taken to compute error statistics - this is non-trivial. For example, exclusive of error statistics computation, bit-no-dither takes <100ms on average. Performance figures will vary based on machine, etc. They are only useful for comparing algorithms against each other within this dataset.

Here’s the encoders at 16 colors with Sierra dithering:

Algorithm	MSE	DSSIM	PHash Distance	Mean ΔE	Max ΔE	ΔE >2.3	ΔE >5.0	Execution Time (ms)
adu	116.85	0.036	39.83	4.02	18.39	66%	33%	332
bit	178.47	0.049	59.79	5.53	16.61	89%	51%	307
bit-merge	95.17	0.030	41.52	3.95	16.16	67%	31%	712
focal	118.57	0.035	48.59	4.36	16.88	72%	34%	2150
k-means	99.36	0.031	43.10	3.99	16.41	67%	31%	637
k-medians	166.88	0.050	60.59	5.48	16.77	88%	52%	5447
median-cut	164.52	0.037	45.28	4.68	16.72	74%	42%	374
octree	459.37	0.085	75.07	7.69	18.89	98%	74%	446
wu	125.84	0.039	50.52	4.48	16.70	75%	39%	906

Re-exports

pub use crate::adu::ADUPaletteBuilder;adu

pub use crate::bit::BitPaletteBuilder;

pub use crate::bitmerge::BitMergePaletteBuilder;bit-merge

pub use crate::focal::FocalPaletteBuilder;focal

pub use crate::kmeans::KMeansPaletteBuilder;k-means

pub use crate::kmedians::KMediansPaletteBuilder;k-medians

pub use crate::median_cut::MedianCutPaletteBuilder;median-cut

pub use crate::octree::OctreePaletteBuilder;octree

pub use crate::wu::WuPaletteBuilder;wu

Modules

aduadu

Use Adaptive Distributive Units to “learn” the image’s color properties and select palette entries.

bit

Encodes a palette by bucketing bit ranges into a power of two number of buckets. This is very fast and produces ok results for most images at larger palette sizes (e.g. 256).

bitmergebit-merge

Uses BitSixelEncoder with k-means and agglomerative merging to build a palette.

dither

A collection of various dithering algorithms that can be used with the SixelEncoder to dither the result.

focalfocal

Use weighted pixels based on the image’s spectral properties to provided weighted input to k-means.

kmeansk-means

Use k-means clustering to determine a palette for the image.

kmediansk-medians

Uses k-medians to build a palette of colors.

median_cutmedian-cut

https://en.wikipedia.org/wiki/Median_cut

octreeoctree

Uses an octree to build a palette from an image.

wuwu

Uses Wu’s quantization algorithm to build a palette from an image.

Structs

SixelEncoder

The main type for performing sixel encoding.

Traits

PaletteBuilder

A trait for types that perform quantization of an image to a target palette size.

Type Aliases

ADUSixelEncoderadu

BitMergeSixelEncoderbit-merge

BitMergeSixelEncoderBestbit-merge

BitMergeSixelEncoderBetterbit-merge

BitMergeSixelEncoderLowbit-merge

BitSixelEncoder

FocalSixelEncoderfocal

KMeansSixelEncoderk-means

KMediansSixelEncoderk-medians

MedianCutSixelEncodermedian-cut

OctreeSixelEncoderoctree

WuSixelEncoderwu