Smart Cropping Unexpectedly Applies Rule of Thirds with no off mechanism

[tomjn]

I'm dealing with an issue where a client has recently moved to Tachyon, but now headshots that were centred are postioned off to the side.

Further investigation reveals that smart media cropping tool is applying the smart crop strategy, and the smart cropping library is applying the rule of thirds, shifting the faces to the left or right and causing issues for stakeholders.

tachyon/src/lib.ts

Line 255 in 24cbb12

// apply smart crop if available

I can find no mechanism to turn the rule of thirds off and have resorted to disabling smart cropping as a feature in the clients codebase to mitigate the issue.

I can reliably recreate the problem and toggle it using https://29a.ch/sandbox/2014/smartcrop/examples/testbed.html by checking and unchecking the rule of thirds box.

[rmccue]

Smart cropping by its nature isn't perfect, but rather a best guess at a way to crop an image. It's a heuristic approach, so overriding it manually is recommended (eg via Smart Media).

If this is for a customer on Altis, I'd suggest manually adjusting the crops via Smart Media's admin UI.

Do you have an example image you can provide which is cropping "incorrectly"?

[tomjn]

Not without revealing the client name publicly, and it was actually smart media that caused the problem by setting the smart cropping strategy on URLs that resize but don't specify a cropping strategy. Investigation shows this is undocumented behaviour that affects all Tachon users.

It's a heuristic approach, so overriding it manually is recommended

The heuristic finds the faces in the expected position, but instead of centering them it places them off to the side changing the default Tachyon behaviour, hence the issue. Manually adjusting what could be thousands of images was never an option.