Please offer ZIP compression when saving as TIFF

Currently, when saving an image in TIFF format, Acorn offers only PackBits and LZW compression options. The TIFF specification also accommodates ZIP compression, which works slightly better than LZW in 8-bits-per-channel files, and massively better than LZW in 16 bits-per-channel files (which LZW can actually make larger than the uncompressed file). All of these options (including both LZW and ZIP with or without Prediction) have long been available in Thorsten Lemke’s venerable GraphicConverter app.

I see that Acorn is able to open a TIFF saved from GC using ZIP+Prediction compression, so that works. Please add the ability to save in that format as well. Thank you.

Better yet, in addition to the specific compression algorithms, offer the option “Best” (or “Best Lossless” if JPEG compression is offered; see below), preferably as the default, which would attempt all the lossless compression methods (as well as uncompressed) and automatically use whichever option results in the smallest file.

Perhaps it’s worth mentioning that TIFF supports using lossy JPEG compression as well, so that could be yet another option, though if offered it should be displayed as “JPEG (lossy)” to make clear that it’s not lossless. (I suppose one might want to use TIFF–JPEG instead of direct JPEG if in a given use case it were very important to use the metadata tagging features of the TIFF format, but lossless compression were not needed.)

I’ll consider this for a future release, though I’m wondering why anyone would pick TIFF with JPEG compression, instead of encoding as JPEG?

Thanks for the feedback!

-gus

I’ll consider this for a future release

Thank you!

I’m wondering why anyone would pick TIFF with JPEG compression, instead of encoding as JPEG?

As I said above, I can imagine that the TIFF metadata tagging features might be very useful in certain cases, but I’m only speculating.

Interestingly, as I discovered this week, when one uses Image Capture to make a flatbed scan saved to TIFF format, and the bounding box is orthogonal (zero rotation), LZW compression is used… but if the bounding box is even slightly rotated, JPEG compression is used! AFAIK this is not documented anywhere, and it strikes me as bizarre, but it’s true. (This is how the subject of TIFF compression came to my attention recently.)