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TIFF thumbnailing fails and page count is wrong
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Description

I recently uploaded some tiff files from the National Library of Sweden. They are all quite big but display properly as one-page TIFFs in both Gimp an ImageMagick (display) on my Ubuntu machine.

Upon uploading them to Commons they are however interpreted as two-page files and the generated thumbnails are entirely (or almost entirely) white. I've had the two-page issue before with tiffs from another source but the white thumbnails are new.

The files can be found at Category:Maps digitised by the National Library of Sweden

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Restricted Application added a subscriber: Aklapper. · View Herald TranscriptJan 20 2015, 3:35 PM

We have a bug with tiff files that have 16 bit colour channels when > 50 mp which sounds likexwhat you describe

Ah, thanks. Is this the same as T54045 or is there another ticket?

Will create thumbnails manually then and tag with {{LargeTIFF}}.

Its the same as T54045#546265 (Arguably though, that comment should be broken out into a separate bug).

btw, to tell if its that bug, or something else, on the exif section of the image page, under extended details, if the bits per component reads 16, then its this issue.

Thanks for the tip. Is the two-page issue also created by the same bug?

Btw. I assume simply running convert x.tif y.png should give me something which should thumbnail correctly, or will there be a similar issue with the png?

Thanks for the tip. Is the two-page issue also created by the same bug?

I'm not sure what the cause of the two page thing is, but its unrelated. Maybe a bug in tiffinfo. Its probably a "thumbnail" image being picked up as an extra page.

Btw. I assume simply running convert x.tif y.png should give me something which should thumbnail correctly, or will there be a similar issue with the png?

That should be fine.