Add code to create a png from a string

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2018 
+Copyright (c) 2018 lamadeus <[email protected]> (https://github.com/lamadeus)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

es/index.js

@@ -0,0 +1,17 @@
+import { Buffer } from 'buffer';
+import { createPng } from './png';
+import { prependLength } from './utils';
+
+
+/**
+ * Encode the given data to png.
+ *
+ * @param {string} data
+ * @returns {Promise<Buffer>}
+ */
+export function encode(data) {
+	const bytes = Buffer.from(data, 'utf8');
+	const pixelData = prependLength(bytes);
+
+	return createPng(pixelData);
+}

es/png.js

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+import { Buffer } from 'buffer';
+import { crc32 } from 'crc';
+import zlib from 'zlib';
+
+
+/**
+ * PNG header.
+ *
+ * @type {Buffer}
+ */
+const PNG_HEADER = Buffer.from([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]);
+
+/**
+ * Max width of the png.
+ *
+ * @type {number}
+ */
+const MAX_WIDTH = 1024;
+
+/**
+ * Create a chunk of the given type with the given data.
+ *
+ * @param type
+ * @param data
+ * @returns {Buffer}
+ */
+function createChunk(type, data) {
+	const length = typeof data != 'undefined' ? data.length : 0;
+	const chunk = Buffer.alloc(4 + 4 + length + 4);
+
+	chunk.writeUInt32BE(length, 0);
+	chunk.fill(type, 4, 8, 'utf8');
+	if (typeof data != 'undefined') {
+		chunk.fill(data, 8, chunk.length - 4);
+	}
+	chunk.writeUInt32BE(crc32(chunk.slice(4, -4)), chunk.length - 4);
+
+	return chunk;
+}
+
+/**
+ * Create the IHDR chunk.
+ *
+ * @param width
+ * @param height
+ * @returns {Buffer}
+ */
+function createIHDRChunk(width, height) {
+	const data = Buffer.alloc(13);
+
+	// Width
+	data.writeUInt32BE(width);
+	// Height
+	data.writeUInt32BE(height, 4);
+	// Bit depth
+	data.writeUInt8(8, 8);
+	// RGBA mode
+	data.writeUInt8(6, 9);
+	// No compression
+	data.writeUInt8(0, 10);
+	// No filter
+	data.writeUInt8(0, 11);
+	// No interlacing
+	data.writeUInt8(0, 12);
+
+	return createChunk('IHDR', data);
+}
+
+/**
+ * Create the IDAT chunk.
+ *
+ * @param data
+ * @returns {Buffer}
+ */
+function createIDATChunk(data) {
+	return createChunk('IDAT', data);
+}
+
+/**
+ * Create the IEND chunk.
+ *
+ * @returns {Buffer}
+ */
+function createIENDChunk() {
+	return createChunk('IEND');
+}
+
+/**
+ * Create a png from the given pixel data.
+ *
+ * @param pixelData
+ * @returns {Promise<Buffer>}
+ */
+export function createPng(pixelData) {
+	const length = pixelData.length + 4 - (pixelData.length % 4);
+	const pixels = Math.ceil(length / 4);
+	const width = Math.min(pixels, MAX_WIDTH);
+	const height = Math.ceil(pixels / MAX_WIDTH);
+	const bytesPerRow = width * 4;
+	const buffer = Buffer.alloc((bytesPerRow + 1) * height);
+
+	// Write pixel data to buffer
+	for (let y = 0; y < height; y += 1) {
+		const offset = y * bytesPerRow;
+		const rowData = pixelData.slice(offset, offset + bytesPerRow);
+		const rowStartX = offset + y + 1;
+		const rowEndX = rowStartX + bytesPerRow;
+
+		buffer.writeUInt8(0, offset + y);
+		buffer.fill(rowData, rowStartX, rowEndX);
+	}
+
+	return new Promise((resolve, reject) => {
+		zlib.deflate(buffer, (error, deflated) => {
+			if (error) {
+				reject(error);
+				return;
+			}
+
+			resolve(Buffer.concat([
+				PNG_HEADER,
+				createIHDRChunk(width, height),
+				createIDATChunk(deflated),
+				createIENDChunk(),
+			]));
+		});
+	});
+}

es/utils.js

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+import { Buffer } from 'buffer';
+
+
+/**
+ * Prepend length to the data.
+ *
+ * @param data
+ * @returns {Buffer}
+ */
+export function prependLength(data) {
+	const lengthAsBytes = Buffer.alloc(4);
+
+	lengthAsBytes.writeUInt32BE(data.length);
+
+	return Buffer.concat([lengthAsBytes, data]);
+}

index.js

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+export * from './es';

package.json

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+{
+	"name": "data-to-png",
+	"version": "1.0.0",
+	"description": "A Javascript utility that lets you encode any data to png.",
+	"main": "index.js",
+	"scripts": {
+		"test": "echo \"Error: no test specified\" && exit 1"
+	},
+	"repository": {
+		"type": "git",
+		"url": "git+https://github.com/lamadeus/data-to-png.git"
+	},
+	"keywords": [
+		"javascript",
+		"encode",
+		"decode",
+		"png"
+	],
+	"author": "lamadeus <[email protected]>",
+	"license": "MIT",
+	"bugs": {
+		"url": "https://github.com/lamadeus/data-to-png/issues"
+	},
+	"homepage": "https://github.com/lamadeus/data-to-png#readme",
+	"dependencies": {
+		"buffer": "^5.2.1",
+		"crc": "^3.8.0",
+		"zlib": "^1.0.5"
+	}
+}

yarn.lock

@@ -0,0 +1,28 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+base64-js@^1.0.2:
+  version "1.3.0"
+  resolved "https://registry.yarnpkg.com/base64-js/-/base64-js-1.3.0.tgz#cab1e6118f051095e58b5281aea8c1cd22bfc0e3"
+
+buffer@^5.1.0, buffer@^5.2.1:
+  version "5.2.1"
+  resolved "https://registry.yarnpkg.com/buffer/-/buffer-5.2.1.tgz#dd57fa0f109ac59c602479044dca7b8b3d0b71d6"
+  dependencies:
+    base64-js "^1.0.2"
+    ieee754 "^1.1.4"
+
+crc@^3.8.0:
+  version "3.8.0"
+  resolved "https://registry.yarnpkg.com/crc/-/crc-3.8.0.tgz#ad60269c2c856f8c299e2c4cc0de4556914056c6"
+  dependencies:
+    buffer "^5.1.0"
+
+ieee754@^1.1.4:
+  version "1.1.12"
+  resolved "https://registry.yarnpkg.com/ieee754/-/ieee754-1.1.12.tgz#50bf24e5b9c8bb98af4964c941cdb0918da7b60b"
+
+zlib@^1.0.5:
+  version "1.0.5"
+  resolved "https://registry.yarnpkg.com/zlib/-/zlib-1.0.5.tgz#6e7c972fc371c645a6afb03ab14769def114fcc0"