@thi.ng/grid-iterators

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About
Status
Related packages
Installation
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Usage examples
API
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About

2D grid and shape iterators w/ multiple orderings.

Provides the altogether 25 following orderings (excluding symmetries) to generate grid coordinates, including iterators for shape rasterization, drawing, clipping, filling, processing in general:

Columns

anim

Source

Also see the filtered version columnEnds2d(), which only includes the end points of each column.

Diagonal (45 degrees)

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Also see the filtered version diagonalEnds2d(), which only includes the end points of the diagonals.

Diagonal with configurable slope

anim anim

Source

Interleave columns

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Supports custom strides... example uses step = 4

Interleave rows

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Supports custom strides... example uses step = 4

Random

anim

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Supports custom PRNG implementations via IRandom interface defined in @thi.ng/random

Rows

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Also see the filtered version rowEnds2d(), which only includes the end points of each row.

Zigzag rows

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Some functions have been ported from Christopher Kulla's Java-based Sunflow renderer.

For more basic 2D/3D grid iteration, also see range2d() & range3d() in @thi.ng/transducers.

Mirror symmetries & arbitrary coordinate transformations

All of the above mentioned grid iterators support point (grid coordinate) transformations to create variations of their base orderings. The package provides the flipX, flipY and flipXY preset transforms to mirror one or both axes, but custom transforms can be easily implemented via the same underlying mechanism. These transforms can be specified via the tx option passed to the iterators (see code example further below).

Flood filling

The floodFill() iterator can be used to iterate arbitrary 2D grids using an user-provided predicate function. The function recursively explores (in a row-major manner) the space in the [0,0]..(width,height) interval, starting at given x,y and continues as long given predicate function returns a truthy value. Any eligible 90-degree connected regions will be found and iterated recursively. The predicate function is used to select eligible grid cells (e.g. "pixels" of sorts).

import { floodFill } from "@thi.ng/grid-iterators";

// source "image"
const img = [
    "█", " ", " ", " ", "█",
    "█", " ", "█", " ", " ",
    " ", " ", "█", " ", "█",
    " ", "█", "█", " ", " ",
    " ", " ", " ", "█", "█",
];

// flood fill iterator from point (1,0)
// only accept " " as source pixel value
// image size is 5x5
const region = floodFill((x, y) => img[x + y * 5] === " ", 1, 0, 5, 5);

// label filled pixels using increasing ASCII values
let ascii = 65; // "A"
for(let [x,y] of region) img[x + y * 5] = String.fromCharCode(ascii++);

// result image showing fill order
img
// [
//   "█", "A", "B", "C", "█",
//   "█", "I", "█", "D", "E",
//   "K", "J", "█", "F", "█",
//   "L", "█", "█", "G", "H",
//   "M", "N", "O", "█", "█"
// ]

Shape iterators

Additionally, the following shape iterators are available, all also with optional clipping:

circle (Bresenham)
hline
vline
line (Bresenham)

Status

STABLE - used in production

Search or submit any issues for this package

Related packages

@thi.ng/morton - Z-order curve / Morton encoding, decoding & range extraction for arbitrary dimensions
@thi.ng/rasterize - 2D shape drawing & rasterization
@thi.ng/transducers - Lightweight transducer implementations for ES6 / TypeScript

Installation

yarn add @thi.ng/grid-iterators

ES module import:

<script type="module" src="https://cdn.skypack.dev/@thi.ng/grid-iterators"></script>

Skypack documentation

For Node.js REPL:

const gridIterators = await import("@thi.ng/grid-iterators");

Package sizes (brotli'd, pre-treeshake): ESM: 2.58 KB

Dependencies

Usage examples

Several projects in this repo's /examples directory are using this package:

Description	Live demo	Source
Visualization of different grid iterator strategies	Demo	Source
Generating pure CSS image transitions	Demo	Source
Multi-layer vectorization & dithering of bitmap images	Demo	Source

API

Generated API docs

import * as gi from "@thi.ng/grid-iterators";

[...gi.zigzagRows2d({ cols: 4, rows: 4 })]

// [
//   [ 0, 0 ], [ 1, 0 ], [ 2, 0 ], [ 3, 0 ],
//   [ 3, 1 ], [ 2, 1 ], [ 1, 1 ], [ 0, 1 ],
//   [ 0, 2 ], [ 1, 2 ], [ 2, 2 ], [ 3, 2 ],
//   [ 3, 3 ], [ 2, 3 ], [ 1, 3 ], [ 0, 3 ]
// ]

// with applied horizontal mirroring
// also, if `rows` is missing, it defaults to same value as `cols`
[...gi.zigzagRows2d({ cols: 4, tx: gi.flipX })]
// [
//   [ 3, 0 ], [ 2, 0 ], [ 1, 0 ], [ 0, 0 ],
//   [ 0, 1 ], [ 1, 1 ], [ 2, 1 ], [ 3, 1 ],
//   [ 3, 2 ], [ 2, 2 ], [ 1, 2 ], [ 0, 2 ],
//   [ 0, 3 ], [ 1, 3 ], [ 2, 3 ], [ 3, 3 ]
// ]

Authors

Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-grid-iterators,
  title = "@thi.ng/grid-iterators",
  author = "Karsten Schmidt",
  note = "https://thi.ng/grid-iterators",
  year = 2019
}