Preview API: different aspect ratio / scale options

[felix-schwarz]

Talking with @DeepDiver1975 about the Preview API, the topic of aspect ratio scaling came up. Right now, it appears the y parameter is ignored if the aspect ratio parameter a is set.

This works for wide images, but would return a larger-than-requested image for portrait images.

Landscape Example:

• image size: 200 x 100
• maximum size: 20 x 20
• returned image size: 20 x 10

Portrait Example:

• image size: 100 x 200
• maximum size: 20 x 20
• returned image size: 20 x 40

Ideally, Preview API would allow clients to pick one of these scaling methods:

• ignore: ignore aspect ratio

• aspect fit: scale image to fit the requested size while maintaining the aspect ratio. The resulting image can be smaller than the requested size.

• aspect fill: scale image to fill the requested size while maintaining the aspect ratio, cutting off parts of the image if needed. The resulting image is exactly the requested size.

[ownclouders]

GitMate.io thinks possibly related issues are #13516 (Previews with aspect ratio need to be properly cached), #16551 (Thumbnail API asks for a preview twice each time), #19548 (Add option to configure preview (and thumbnail, ect.) location), #19958 (Streaming API?), and #6550 ("Enable Previews" config option should default to "false").

[michaelstingl]

There have been some limitations in the past:

• Missing methods from the PreviewManager  #12772
• Thumbnail generation: does not obey aspect ratio / max values for x and y #16250
• Resized images android#1599

Maybe this can be done right with the new implementation…

[ownclouders]

Hey, this issue has been closed because the label status/STALE is set and there were no updates for 7 days. Feel free to reopen this issue if you deem it appropriate.

(This is an automated comment from GitMate.io.)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 10 days if no further activity occurs. Thank you for your contributions.