Re^4: How to keep Imager's image files small ?

You'd be wrong.

Imager can write to bmp, png, tif, ico at 4 bits per pixel, though png was only added to that list in Imager 0.90 (April 2012).

GIF is a special case - if the stored palette is 4 bits (16 colors) then it will start compression with a 5 bit code size, there's none of the packing 2 indices per byte as for the other formats.

Comment on Re^4: How to keep Imager's image files small ?

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Re^5: How to keep Imager's image files small ? by BrowserUk (Patriarch) on Jul 28, 2012 at 00:33 UTC
I stand corrected. Thankyou. Out of interest, what triggers the writing of a 4-bit per pel .png? Is it simply if the image is palettised and only uses 16 colors? I couldn't see any mechanism for forcing it. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. The start of some sanity?	[reply]
Re^6: How to keep Imager's image files small ? by tonyc (Friar) on Jul 28, 2012 at 01:12 UTC
Exactly that. Unlike GIF, PNG supports direct colour, so there's no need for the automatic to_paletted() that writing a GIF does. I've considered adding an optimization option, but it's low priority.	[reply]