How to use graphicsmagick in node.js to crop circle picture (other use any other way to make this on node.js)

Question

How to use graphicsmagick crop circle picture?

(use png transparent background outer circle)

I use graphicsmagick in node.js , or have any other way make this in node.js?

Before: https://i.sstatic.net/B34C5.png

After: https://i.sstatic.net/PWjQW.png

Answer 1

I use another module to solve this problem:

this code is for square image (this.height = this.width)

node-pngjs

var fs = require('fs'),
PNG = require('pngjs').PNG;

fs.createReadStream(__dirname + "/input.png")
    .pipe(new PNG({
        filterType: 4
    }))
    .on('parsed', function() {
    for (var y = 0; y < this.height; y++) {
        for (var x = 0; x < this.width; x++) {
            var idx = (this.width * y + x) << 2;
            var radius = this.height / 2;
            if(y >= Math.sqrt(Math.pow(radius, 2) - Math.pow(x - radius, 2)) + radius || y <= -(Math.sqrt(Math.pow(radius, 2) - Math.pow(x - radius, 2))) + radius) {
                this.data[idx + 3] = 0;
            }
        }
    }
        this.pack().pipe(fs.createWriteStream(__dirname + "/output.png"));
    });