PNG compression

[camsjams]

Thanks for the great library (I migrated from https://github.com/fzaninotto/screenshot-as-a-service).

Is there a way to modify the PNG compression? Or perhaps the color palette?

When I take a screenshot of a black and white document with pure text on a white background, the resulting PNG file is still well over 1MB.

When I use the JPEG or PDF compression, the file is much smaller.

Any tips?

[vbauer]

Yes, I faced with this issue. It looks like you use PhantomJS as an engine for Manet.

I've just make some test with the following request: http://localhost:8891/?url=https%3A%2F%2Fgithub.com%2Fvbauer%2Fmanet&force=true (it is the Github page of Manet) and got the following results:

• PhantomJS: 39.8 MB
• SlimerJS: 1.3 MB

Is it OK for you to switch engine to SlimerJS (as temporary workaround)?

I need some time to research possibilities of some compression library (like this one: https://github.com/imagemin/imagemin)

[vbauer]

I've just integrated imagemin and added compressing for the following formats: JPEG, PNG, GIF, SVG.

It shown the following results for the same page (PNG format):

• PhantomJS: 892 KB
• SlimerJS: 973 KB

I think the result is pretty good, but it takes additional time for compressing.
Compression is switched off by default, to enable it use --compress true.

[vbauer]

Imagemin is a good compressor, but the main problem in the "quality" parameter..

[vbauer]

It looks like I've found the problem. PhantomJS documentation contains mistake: http://phantomjs.org/api/webpage/method/render.html

quality parameter is "An integer between 0 and 100" and in example they use String type. The worst moment that Integer value works fine with JPEG, but doesn't work with PNG.

I've committed new fix, now it should work fine without compress parameter.

[jfix]

I guess it hasn't arrived on npm yet, because updating it doesn't make a change for me (using the --compression true or --compress true parameter). Google.com is still 3.0 MB in size. Any way I can verify I have the right version?

Oops: Just noticed that I was getting the cached version of the screenshot. Setting the --cache=-1 served freshly made screenshots. From 3.0MB to 22KB: FTW! Thanks a lot for you work!

Which also means that it has been published on npm (and it says that you published it 'one day ago': https://www.npmjs.com/package/manet), and that I have the latest version.

However, I still have to explicitly set the --compress true parameter, it doesn't seem to be the default. Without it, I get fat screenshots.

[vbauer]

Actually, --compress parameter works slow for really big screenshots (ex: 1024x20000), so I decided to switch it off by default.

In the next release all PNG images should be much smaller (even without this parameter) and --compress will be as an extra compression option.

[camsjams]

Thanks @vbauer for making this update - it helps out a lot!