Speed Up Resizing?

[glennrp]

Use the Q8 configuration of ImageMagick if you aren't already.

You are right about the reason: the TIFFs get expanded internally
to 64 bits per pixel (Q16) or 32 bits per pixel (Q8).

If you are running *nix, you could investigate the San Diego
Supercomputer Center's image tools. They are not maintained
any more (since 1995) but they are free and can rescale TIFFs
using only 1 bit per pixel for internal storage. You might be able
to incorporate that somehow in your work stream for the initial
scaledown of TIFFs before processing them with ImageMagick.

[anthony]

If you can get them to work scale them to say 4 time your final dimensions, then let IM finish the job to create a grey scale anti-aliased image.

In actual fact this is riught what the -thumbnail operator does to improve its speed, scale, then use a resize on the smaller version, though that will not help you in this case.

[anthony]

Output to JPEG (or GIF) should always be the final step, and these should not be used as the inital source image (unless it can not be helped) as both formats are lossy. They loss information when saving images. GIF because fo color limitations, JPEG because of its compression methodology. They should never be used at the intermediate format between image processing steps, is quality is of concern.

[anthony]

If the JPEG is the final image, that is fine, just try not to further process the JPEG, unless quality loss is acceptable (such as thumbnail generation).