I don’t know of anything that will work exactly the way you describe. The lasso loop slection tool is almost excluseive to drawing apps, and perhaps a few PDF apps. I don’t now of anything that will direclty extract content from web pages using this kind of tool.
That’s not to say it does not exist, just that I’ve never run accross it. If it exists, it will proably be a specialized thrid party browser. I’d start my research there.
That said, I have a couple things you can look at.
One is using a shelf app like Gladys alongside your favorite webbrowser. You are limited to the selectiont tools of the browser (pencile or finger) but it’s fairly easy to collect content. It’s stong point is that you can collect content from several apps, and then paste it back into whatever other app you want. I like Gladys. It’s flexible, and allows you to specify the kind of content you want to paste (copied content often has more than one type: html, image, text)
The weakness of whatever method is that you are limited to methods the source app lets you use to select content. The strength is that it works with almost all apps, acting as a kind of super clipboard.
The other app I suggset you look at is Liquid Text. It’s primarily used with PDF files, but it has a web browser that lets you convert webpages to PDF. While you can not lasso stuff, it does allow you to select text, images, or just chunks of the document. It takes alittle practice to get the selection type youwant (image, text, bock of page), but works fairly well with the pencil. Non text selections are always retangles. Text is text.
The strength is that it works will pretty much every part of the document. It’s weakness is that using the collected content outside the app si limited. You can export PDF’s, note style pages, and other stuff. What you can’t do is directly paste the collected content into other apps.
Which of these would be the most useful to you would depend on what youa re trying to accomplish. If you are pulling thigs out of documents to study or research, the Liquid Text should be better. That’s what it is designed to do. If you are collecting content for a project, then a shelf app like Gladys will be better.
Good luck.