jjrv

Image dithering using a low discrepancy quasirandom sequence

Inspired by and image sourced from: https://liamappelbe.medium.com/dizzy-dithering-2ae76dbceba1

Animated example using sigma 1.5: https://github.com/user-attachments/assets/b1d8a059-a142-4007-8417-c013229f5577

jjrv

// Fast sixel encoder for indexed color bitmap terminal graphics
// Copyright 2025- Juha Järvi
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM

jjrv

// Copyright 2025- Juha Järvi
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR

jjrv

const std = @import("std");

pub const Sizes = @Vector(4, u6);
const debug = true;

pub const BitReader = struct {
    word_buf: [*]const u32,
    bit_count: u6,
    bits: u64,

jjrv

/*
Map index along 2D Hilbert curve to coordinates (x,y) and back,
branchless using bit twiddling.

Copyright 2012, 2024 Juha Järvi

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH

jjrv

Copyright 2024- Juha Järvi

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR

jjrv

import { LCS, Interned } from './lcs';

export class Histogram<Token> {

	constructor(before: Token[], after: Token[]) {
		let prefix = 0;
		let beforeEnd = before.length;
		let afterEnd = after.length;

		// Skip common prefix.

jjrv

We want to find a perspective camera lookat direction $\hat{d}$ so that a given direction $\hat{a}$ in world coordinates becomes $\hat{b}$ in camera coordinates. The camera rotation matrix $R$ is defined by:

World local up vector:

$$ \hat{y} = \begin{bmatrix} 0 & 1 & 0 \end{bmatrix}^{\mkern-1.5mu\mathsf{T}} $$

Camera lookat vector:

jjrv

const std = @import("std");

/// Given an example struct with methods, create a function that produces vtables for similarly shaped structs.
/// A vtable contains function pointers to all the struct methods, with the struct type erased.
/// All structs should have an init function that takes an allocator as the first parameter and stores it in a field called "allocator".
/// At most 2 parameters are supported for methods (in addition to the initial self parameter).
pub fn VTableShape(comptime Template: type) type {
    var fields = @typeInfo(struct { //
        deinit: *const fn (*anyopaque) void,
    }).Struct.fields;

jjrv

Copyright (c) 2020- Juha Järvi

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR