1945768 - captureScreenshot format type "image/jpg" gets converted to "image/png"

Status: NEW

(Remote Protocol :: WebDriver BiDi, defect, P3)

Description

[Julian Descottes [:jdescottes]]

Not sure if this is actually a defect, but I stumbled upon this when writing the blog post for 135.
We advertise using "image/png" or "image/jpg", but the second one is actually not recognized properly and will produce a png. To create a JPG, one should use "image/jpeg". This is quite important, because the quality parameter only has an impact with image/jpeg.

I wonder if we should restrict values to known supported types, and throw an UnsupportedOperationError otherwise?

Comment 1

[Henrik Skupin [:whimboo][⌚️UTC+2]]

Oh, good catch. Yes we should fix that sooner than later as best for the 135 release. Maybe we should revert the announcement in the blog post and on MDN and bring it up again in the next release? It doesn't make sense to announce a feature that actually doesn't work. :/

Comment 2

[Julian Descottes [:jdescottes]]

The feature works fine if you provide the expected MIME type "image/jpeg", but it looks like "image/jpg" is actually not a valid / known MIME type, so it falls back to image/png when using canvas' toDataURL. I think spec-wise everything is fine, it's just easy to make the same mistake for end users.

I will send a PR to update our MDN release note and mention the correct MIME type, but I wouldn't backout anything at this point?

Comment 3

[Henrik Skupin [:whimboo][⌚️UTC+2]]

(In reply to Julian Descottes [:jdescottes] from comment #2)

I will send a PR to update our MDN release note and mention the correct MIME type, but I wouldn't backout anything at this point?

If it's just the fallback that is wrong then I agree. No need to change the release notes.