Only works with PNG images, fails on JPG or WebP about puppeteer-screenshot-tester

[burnpiro]

Hi, the error is caused by reasembleJS and it's because it only supports .png files (I'm not sure if other formats with transparency are supported but neither .jpg nor .webm are one of them). You need transparency to create a diff, but I guess we could work with white or black backgrounds as well. I could try to rewrite that part of the code and replace transparency with a solid background. Let me look at that over the weekend.

[wadeharrell]

saw that, figured you knew the guy working on node-resemble.js ;)

Unfortunately I don't see any npm package for webp as straight forward as pngjs, but webp does support alpha https://developers.google.com/speed/webp/gallery2 so in theory it should be able to do everything you can with PNG at a much smaller file size; JPG is out of luck in that regard though.

In the context of puppeteer-screenshot-tester you know that you have chrome, so perhaps could leverage some canvas APIs? i.e. https://stackoverflow.com/a/55896125
I could see the case for even converting webp & jpg to PNG before sending them to resemble, then converting the diff to the desired output on the way back.

p.s. thanks for the quick response!

[burnpiro]

Fixed in v1.5.0.

Additionally, there is a new option to change the default compression levels for images. This might help with reducing the size if you want.