Improve PNG decompression implementation

[EzraBrooks]

Use fast-png to unify the implementation between Node.js
and browser, and unbork Web Worker support (fixes #859)

[EzraBrooks]

Hey @tosscaster could you test this? I don't have a Web Worker environment to test this in.

Or even helping add an automated test would be awesome.

[EzraBrooks]

okay, added a test. now we actually know for sure that PNG compression works!

[EzraBrooks]

The test timeout isn't from the roslibjs side of things. The initial run before the V8 JIT optimizes it only takes 3.7ms, and then subsequent runs take under half a millisecond.

Decompressing PNG: 3.773ms
Decompressing PNG: 0.223ms
Decompressing PNG: 0.154ms
Decompressing PNG: 0.159ms
Decompressing PNG: 0.319ms

[EzraBrooks]

@bjsowa @sea-bass it looks like there's something wrong with rosbridge here, in ROS 2 specifically.

[bjsowa]

I'll try to take a look later today

[bjsowa]

@EzraBrooks I see what's the problem. There was a bug with PNG compression in rosbridge which was fixed some time ago (RobotWebTools/rosbridge_suite#1045). The fix is included in the newest versions of rosbridge which I release a week ago.

I tried the example against the newest version of rosbridge in Jazzy and Rolling and it worked.

[EzraBrooks]

So does the introduction of this test need to wait til the next sync?

[bjsowa]

So does the introduction of this test need to wait til the next sync?

Unless we change the dockerfile to use ROS testing repository or build rosbridge itself.

[EzraBrooks]

Given that the code works, I'm inclined to mark the test skipped and merge this. Are you okay with that?

[EzraBrooks]

Note to self: remove pngparse type declaration file here before merging because the dependency itself is gone

[bjsowa]

Given that the code works, I'm inclined to mark the test skipped and merge this. Are you okay with that?

I'm fine with that

[bjsowa]

There should be a new sync for each ros distro by the end of this month. After the sync and when the docker images are updated, we should be able to reenable the test.