in reply to Re^3: How to keep Imager's image files small ?
in thread 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.

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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?

      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.