Quick PNG circle clipper

clip-circle.js

#!/usr/bin/env node

const path = require('path');
const fs = require('fs');
const cmdr = require('commander');
//this requires Cairo: https://www.npmjs.com/package/canvas
//  brew install pkg-config cairo libpng jpeg giflib
const {createCanvas, Image} = require('canvas');

  cmdr
    .option('-p, --path <n>', 'Path to png to crop', (p)=>{return path.resolve(p)||undefined;})
    .option('-m, --margin <n>', 'width of circle margin in pixels', (m)=>{return isNaN(parseInt(m))?undefined:parseInt(m);})
    .parse(process.argv);

console.log('Manipulating : '+cmdr.path);

if(!cmdr.path){console.log('No --path given');process.exit();}

fs.readFile(cmdr.path, function(err, src){
  const margin = cmdr.margin||10;
  if (err) throw err;

  var img = new Image;
  img.src = src;

  var side = img.width>img.height?img.height:img.width

  var canvas = createCanvas(side+2, side+2);
  var ctx = canvas.getContext('2d');

  //linear-gradient(15deg, #44dd44, #dddd44);
  /*
  var g=ctx.createLinearGradient(side-10,0,0,side-10);
  g.addColorStop(0,"#dddd44");
  g.addColorStop(1,"#44dd44");
  ctx.fillStyle=g;
  ctx.fillRect(0, 0, side, side);
  */

  // Create a circle
    ctx.beginPath();

    ctx.arc(side/2, side/2, (side/2)-margin, 0, Math.PI * 2, true);

    // Clip to the current path
    ctx.clip();

  ctx.drawImage(img, (img.width-side)/2, (img.height-side)/2, side, side, 0, 0, side, side);

  fs.writeFile(cmdr.path.replace(/\.(jpg|png)$/,".clipped.png"), canvas.toDataURL().replace(/^data:image\/png;base64,/, ""), 'base64', function(err) {
    if(err)console.log(err);
    else console.log('Complete! '+cmdr.path.replace(/\.(jpg|png)$/,".clipped.png"));
  });
});

Throwing this in before the cropped image, gives a nice gradient.
I'll add it once I've thought about what command line options it should have.

//linear-gradient(15deg, #44dd44, #dddd44);
  var g=ctx.createLinearGradient(img.width-10,0,0,img.height-10);
  g.addColorStop(0,"#dddd44");
  g.addColorStop(1,"#44dd44");
  ctx.fillStyle=g;
  ctx.fillRect(0, 0, img.width, img.height);

(The comment is what I was aiming for, but it's more approximate and just for reference)

Newer version crops down non-square images, uses newer node-canvas version and doesn't overwrite .jpg files