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Old 10-15-2019, 02:28 PM   #11
ratinox
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Quote:
Originally Posted by davidfor View Post
And as @NiLuJe, Kobo actually renders in colour. I assume it is writing to the screen that does the gray-scaling. I suspect you won't get any noticeable performance benefit. I would say that space is the only advantage and you can test this manually to see if it is actually worthwhile following it up. Try what @theducks suggested.
Pretty much. Blitting to the display is what converts color to greyscale so greyscale conversion of source images isn't going to get you much of anything for performance.

Converting from 16/24/32-bit deep color to 8-bit greyscale may save some space but the reason I do it is to minimize artifacts when the display hardware does it on the fly. My commands include some blur and fuzz in order to reduce visible artifacts and take advantage of efficiencies in the JPEG libraries.

Using jpegtran to optimize JPEG files or optipng to optimize PNG files may help reduce image file sizes by a few percent if they haven't already been optimized.

Performance gains can be had by scaling to the native resolution of the display so that the renderer doesn't have to spend procesor cycles (and battery) scaling on the fly. This can either increase or reduce image file sizes depending on the source resolutions and depths.
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