Exported PNG not transparent

[rinne]

Expected Behaviour

1. Canvas should by default be transparent and so should in my opinion be the exported bitmap if the export format supports that.

Actual Behaviour

var fs = require('fs');
var PImage = require('pureimage');
var img1 = PImage.make(100,50);
PImage.encodePNGToStream(img1, fs.createWriteStream('out.png')).then(()=> {
    console.log("wrote out the png file to out.png");
}).catch((e)=>{
    console.log("there was an error writing");
});

Results an opaque black PNG.

[elmbrent]

var fs = require('fs');
var PImage = require('pureimage');
var img1 = PImage.make(100,50);
var context = img.getContext('2d')
context.clearRect(0, 0, 100,50)
PImage.encodePNGToStream(img1, fs.createWriteStream('out.png')).then(()=> {
    console.log("wrote out the png file to out.png");
}).catch((e)=>{
    console.log("there was an error writing");
});

You need to add a clearRect and then also set to same height and width of your canvas.

[joshmarinacci]

You are right. According to the spec a canvas is transparent by default. I've confirmed this experimentally as well.

I've just pushed back a change which makes the bitmap be clear by default. This should automatically work with exported PNGs as well.

Note that the spec also indicates you can create an opaque canvas by passing an option to getContext(). We should support this in the future.

https://html.spec.whatwg.org/multipage/canvas.html#the-canvas-element