Using a hidden HTML5 canvas as an image editor + translucent widgets

I have been working on extending my transparent widget script to support blurred translucent backgrounds, just like the Batteries widget. This was much more difficult than I had anticipated, since the built-in DrawContext doesn’t support blurring or blending modes.

Instead… I found out that you can pass HTML and Javascript code to a WebView object, have it render the page and execute Javascript, and then pass a value back to the script — all without displaying it on screen. And since Scriptable allows you to encode and decode images as base 64 data strings, you can easily pass images to and from the WebView. Here is some example code that takes an image and processes it using this method.

In my case, I used the amazing StackBlur algorithm and some additional algebra to create translucent widget backgrounds. Here is the script to create these backgrounds. Enjoy!


I have another approach where you set a background image like what you did on the transparent widget script and then add a semi-transparent linear gradient. Works just as well so I added it to my no-background module.

Nice! The semi-transparent gradient is definitely more straightforward, and the result looks nice. The only reason my code is so convoluted is because I was trying to match the Batteries widget exactly - to do that, you need to mess with the colors a bit further.

Yes, The blur provides a better effect than just plain alpha.