Texel + Saving Canvas PNG

about.md

Saving GIF/MP4 Frames with Texel

The above GIF was rendered with Canvas2D and JavaScript. I used texel, a tool I am developing but have not yet released.

If you want to try this very experimental tool, install the latest working version like so:

npm install [email protected] --global

Copy the index.js example script (see next file) into a new directory:

pbpaste > index.js

Now, start a development server on that file and open the browser:

texel index.js --open

When the page loads, it will save 100 numbered PNG frames in a tmp/ folder relative to your current working directory.

Encode a Movie

To create a GIF with ffmpeg:

ffmpeg -framerate 24 -i tmp/%02d.png -y output.gif

To create an MP4 file:

ffmpeg -framerate 24 -i tmp/%02d.png -y -c:v libx264 -profile:v high -crf 20 -pix_fmt yuv420p output.mp4

Another one using the same technique:

index.js

// The devtool utility for saving canvas frames
import devtool from 'texel/devtool';

// Create canvas
const canvas = document.createElement('canvas');
document.body.appendChild(canvas);

const size = 256;
canvas.width = size;
canvas.height = size;

// Grab 2D canvas context
const context = canvas.getContext('2d');

// How many frames to draw
let frame = 0;
const totalFrames = 100;

// Start drawing
render();

function render () {
  // Clear background to black
  context.fillStyle = 'black';
  context.fillRect(0, 0, size, size);

  // Draw some shapes
  const margin = 40;
  context.strokeStyle = 'white';
  context.beginPath();
  context.moveTo(margin, margin);
  context.lineTo(size - margin, size - margin);
  context.lineWidth = Math.sin(frame / totalFrames * Math.PI) * 20;
  context.stroke();

  // Save a single frame
  devtool.saveCanvas(canvas, {
    // The output folder, relative to current working directory
    output: 'tmp',
    // The current frame index, the filename will be zero-padded
    frame: frame++,
    // The total number of frames in our sequence
    totalFrames
  }).then(() => {
    // Render another frame if necessary
    if (frame < totalFrames) window.requestAnimationFrame(render);
  });
}