Watertext - text watermarking library

Features

• Zero dependencies library, works with NodeJS and in the browser.
• 1.7kb minified (481B gzipped) version.

Quickstart

1. Install library:

npm install --save watertext

2. Watermark regular image with awesome text:

var el = document.getElementsByTagName('img')[0];

// Version 1: callback based (watertext.core.umd.min.js)
watertext(el.src, {text: 'Awesome cat'}, function(err, src){
  el.src = src;
});
// Version 2: promise based (watertext.umd.min.js)
watertext(el.src, {text: 'Awesome cat'})
  .then(function(url){el.src = url;});

Original image	Watermarked image

Versions

There are two main versions:

1. Callback-based vanilla js core.
2. Promise-based (via core-js polyfill) regular.

Depending on usage, there are 3 build options: CommonJS, ES6 module and UMD library. All build are handled by rollup. Backend specific versions (CommonJS and ES6 module) are not minified (~5 Kb) and browser specific UMD comes in minified version only (~1.7 Kb).

Name	CommonJS	ES6 module	UMD
Core (Callback based)	watertext.core.cjs.js	watertext.core.esm.js	watertext.core.umd.min.js
Regular (Promise based)	watertext.cjs.js	watertext.esm.js	watertext.umd.min.js

Development

The library is tiny and the whole source code is in index.js file. It uses ES6 syntax with AirBnB style-guide. Make sure to eslint your code and write jsdoc for every method.

Supported Browsers

npx browserslist

Deployment

Webpack builds both regular and minified versions to dist folder. It uses rollup + bublé because they are faster than webpack + buble and result into smaller build size (~30% reduction).

yarn build

Publish new version with yarn:

yarn publish

Watermarking options

All of the parameters except text are optional. By default, the watermark is placed at the bottom of the image with 10px margin.

Name	Type	Default	Description
text	string	''	Watermark text.
textWidth	number	undefined	Width of watermark in pixels. By default watermark uses 100% of the image width if positioned at the top/bottom and 100% of hight if positioned on the left/right.
textSize	number	12	Watermark text size.
textFont	string	'Sans-serif'	Watermark text font.
textColor	string	'rgb(255, 255, 255)'	Watermark text color.
backgroundColor	string	'rgba(0, 0, 0, 0.4)'	Watermark background color. Default is gray.
position	string	'bottom'	Position of watermark text, one of "top", "left", "right" or "bottom".
margin	number	10	Margin from the nearest edge. Negative margin positions watermark at the opposite edge. Useful for text orientation control for "left" and "right" positioning.
dataURL	Array	[]	Parameters of canvas.toDataURL(type, encoderOptions). Default format type is image/png. Example options: ["image/jpeg", 0.5] or ["image/webp", 0.6].

Links

• base64 to image converter.
• image to base64 converter.

Acknowledgement

• baivong/watermark library hugely inspired this project. While there are a lot of similarities, this library does not require jQuery to watermark images.
• brianium/watermarkjs good multi-purpose watermarking library, inspired ES6 adoption and Webpack usage.
• Cat image is provided by pexels.