Size of Embedded Thumbnails

[MichaelG]

I have a TIFF file created by PTGui. The dimensions are 7500 x 3500 pixels. The size of the file is almost exactly 45 MB. So far, so good.

I happened to discover that the embedded thumbnails are relatively large - in terms of bytes. The dimensions of the thumbnail is 469 x 235 pixels, which seems to be a reasonable size. It turned out that the size of the thumbnail is 440 KB. My first thought was, hm, quite big for such a small image. The reason is, the thumbnail is stored as uncompressed TIFF with 4 byte per pixel. 

My question, is that extrem high quality thumbnail really needed? My answer would be: no. For a single reason: its a thumbnail.

I created a JPG out of the original TIFF with the size of the thumbnail with a medium quality (7 out of 12). The size of the resulting JPG is just 42 KB (after removing all metadata). A reduction by factor 10. Maybe its worth another thought about the type of the embedded thumbnails.

Just my little observation...

Michael

[PTGui Support]

Hi Michael,

You're right. The thing is though, jpeg doesn't support transparency,
that's why PTGui embeds raw tiff data as a thumbnail.

Given that the TIFF output from PTGui will never be used on a website,
and it's 1 or a few % increase, I'd say it's not a big deal?

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

> --
> You received this message because you are subscribed to the Google
> Groups "PTGui Support" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to ptgui+un...@googlegroups.com
> <mailto:ptgui+un...@googlegroups.com>.
> To view this discussion visit https://groups.google.com/d/msgid/
> ptgui/13e50831-9aa6-4ba0-8863-12d9d07746bfn%40googlegroups.com <https://
> groups.google.com/d/msgid/
> ptgui/13e50831-9aa6-4ba0-8863-12d9d07746bfn%40googlegroups.com?
> utm_medium=email&utm_source=footer>.

[MichaelG]

Hi Joost,

I see.

As Einstein told us: Everything is relativ. 1% is obviously a smaller number than 440 KB :-)))))))

440 KB is still a big number. But I see, if preserving the transparency has priority there aren't much alternatives:

- TIFF supports LZW compression for thumbnails: reduction about 50%

- TIFF supports PNG for thumbnail: reduction about 50%. But although PNG is defined the support by readers seems to be limited

- WebP is also possible but is not included in the official TIFF definition: reduction by factor 10 (26 KB). Support by readers seems to be questionable.

To be honest until I came to that topic I didn't know that Photoshop gives me the option how I save a TIFF file: with or without a thumbnail, with or without transparency. Ok, it isn't very obvious that the option "Save Image Pyramid" in the TIFF save dialog is exactly that option. The option seems to be off by default.

Michael