gifencoder-forced-color

gifencoder

Streaming server-side animated (and non-animated) gif generation for node.js

Difference from the original

The transparency color will now be forced instead of attempted. This means setting a transparency color of, for example, 0xff0000 will result in exact red as your replacement color. Before this would have resulted in whatever color is closest to red in your frame which could even result in the transparency color being omitted altogether. The library will now also mix the transparency color with the color in the PNG frame when the alpha value is between 1 and 0 to reduce the amount of hard edges you get in the resulting GIF.

Installation

This module is installed via npm:

$ npm install gifencoder

Streaming API - Duplex Piping with Writes

You can also stream writes of pixel data (or canvas contexts) to the encoder:

const GIFEncoder = require('gifencoder');
const encoder = new GIFEncoder(854, 480);
const pngFileStream = require('png-file-stream');
const fs = require('fs');
 
const stream = pngFileStream('test/**/frame?.png')
  .pipe(encoder.createWriteStream({ repeat: -1, delay: 500, quality: 10 }))
  .pipe(fs.createWriteStream('myanimated.gif'));
 
stream.on('finish', function () {
  // Process generated GIF
});
 
// Alternately, you can wrap the "finish" event in a Promise
await new Promise((resolve, reject) => {
  stream.on('finish', resolve);
  stream.on('error', reject);
});

NB: The chunks that get emitted by your read stream must either by a 1-dimensional bitmap of RGBA data (either an array or Buffer), or a canvas 2D context.

Example: Streaming API - Reads

You can also use a streaming API to receive data:

const GIFEncoder = require('gifencoder');
const { createCanvas } = require('canvas');
const fs = require('fs');
 
const encoder = new GIFEncoder(320, 240);
// stream the results as they are available into myanimated.gif
encoder.createReadStream().pipe(fs.createWriteStream('myanimated.gif'));
 
encoder.start();
encoder.setRepeat(0);   // 0 for repeat, -1 for no-repeat
encoder.setDelay(500);  // frame delay in ms
encoder.setQuality(10); // image quality. 10 is default.
 
// use node-canvas
const canvas = createCanvas(320, 240);
const ctx = canvas.getContext('2d');
 
// red rectangle
ctx.fillStyle = '#ff0000';
ctx.fillRect(0, 0, 320, 240);
encoder.addFrame(ctx);
 
// green rectangle
ctx.fillStyle = '#00ff00';
ctx.fillRect(0, 0, 320, 240);
encoder.addFrame(ctx);
 
// blue rectangle
ctx.fillStyle = '#0000ff';
ctx.fillRect(0, 0, 320, 240);
encoder.addFrame(ctx);
 
encoder.finish();

The above code will generate the following animated GIF:

Contributing

gifencoder is an OPEN Open Source Project. This means that:

Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.

See the CONTRIBUTING.md file for more details.

Contributors

gifencoder is only possible due to the excellent work of the following contributors:

Kevin Weiner	[e-mail]
Thibault Imbert	http://www.bytearray.org/
Eugene Ware	GitHub/eugeneware
Raine Virta	GitHub/raine
Paul Ochoa	GitHub/rochoa
Heikki Pora	GitHub/heikkipora