Alpha channel heuristic when not using ImageWorker doesn't deal with uppercase file extensions

[pascalatfetch]

I tried loading an externally supplied file with .PNG extension, and the alpha channel wasn't clear.
It seems that the heuristic is to just look at the file path, whereas the ImageWorker detects mime types.
That said, there is a flag hasAlpha which the ImageWorker subsequently ignores.

Should the non-worker based code path use a FileReader and do mime type detection as well, or is that too much of a performance hit? At the very least the heuristic string comparison should ignore case.

Looking into this, the code responsible here is this line:

https://github.com/rdkcentral/Lightning/blob/master/src/platforms/browser/WebPlatform.mjs#L270

[wouterlucas]

Hi @pascalatfetch ! Thanks for reporting, I made a tiny fix to straighten this out. Hope to get this into the next release!

[pascalatfetch]

@wouterlucas Great work.

Do you think the image worker ignoring the hasAlpha flag is a potential issue?

[wouterlucas]

During my tests it didn’t seem to ignore the hasAlpha flag on the function itself.

This might be higher up the chain if that is the case, I can look into it but suggest we move this along for the next release.

[pascalatfetch]

I don't think it's super important. Just saw this as a discrepancy.
Maybe I didn't explain what I meant correctly:

When providing the hasAlpha flag to the actual component, it is overriding the heuristic outcome when not running in a worker, but ignored when the worker finishes.

Instead, on worker execution, the hasAlphaChannel result is the only value that is acknowledged.

A fix for that might be to process hasAlpha || hasAlphaChannel when the worker finishes?

[wouterlucas]

ah yes, thanks for clarifying. It indeed seems to be ignored on the image worker because it relies on the mimeType:
https://github.com/rdkcentral/Lightning/blob/master/src/platforms/browser/ImageWorker.mjs#L306

Although I agree that doesn't make sense and it should probably be included when evaluating the alpha also on the image worker. I do think the mimeType itself is solid way to check for the alpha channel, not sure if having an override is necessary at this point.

[elsassph]

It is certainly awkward when image URLs don't include .png somewhere... so we add #.png to the URL in places where we know we want the image to be transparent...