decodePNGFromStream() causes PNGs to lose their transparency. about node-pureimage

[jarrodwatts]

What was your solution for this issue @soulos45?

[joshmarinacci]

Is this bug happening to you? Could you send me a test case to reproduce it? I haven't been able to.

[solace]

Hi! Thanks for this package.

The png renders with a black background using this code fragment. I've tried running the buffer through sharp and changing the background to rgba(255, 255, 255, 0) before passing it into Readable.from and it renders with a white background instead. So it looks like somewhere along the way it's losing the alpha.

const response = await fetch(url);
const buffer = Buffer.from(await response.arrayBuffer());
const stream = Readable.from(buffer);
const img = await PureImage.decodePNGFromStream(stream);
ctx.drawImage(img, x, y, w, h);

I'll see if I can sort out a demo at the weekend.

[solace]

Link to repro: https://codesandbox.io/s/node-js-test-forked-kxp643

Nav to /image in the sandbox browser to trigger download of the generated image which I have also attached.

Note that the react icon should be transparent, not black. This demo also demonstrates a clipping issue I am experiencing which I will detail in a new ticket.

Currently working around this by passing the buffer through sharp and applying the matching background colour before sending it to decodePNGFromStream.