Quote:
Originally Posted by innocenat
While this is can be technically correct, I still find that for most manga image, PNG is still bigger than JPG, so JPG is still more space efficient. It's true that adding dithering will result in worse compression in JPEG, but such is life. All digital cameras use dithering and still save in JPEG. And KCC still use Floyd Steinburg dithering to this day.
The operation order problem stated in the pull request is absolutely correct but has since been fixed.
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Hardly on topic rant:
Digital cameras don't dither, they tend to compress jpegs a little even on highest compression settings. Either that, or the fact that jpegs are 8-bit only, may cause some artefacts. Jpegs are secondary quality, mainly it's RAW's that are used for serious work. RAW is compete sensors read-out, it handles 16-bit, but is limited by dynamic range of digital sensors, so it's colour capturing capabilities range from 12 to 14 bits.
Regarding quality difference and dithering of PNG's and Jpeg's. PNG is superior format, no questions about that, it supports 16bit and is entirely lossless. But you can safely go with jpegs at maximum quality (low compression), or even have them slightly compressed at around 90-95%, and you won't be able to see any differences at all. If you 'compress' jpeg at maximum quality, it'll be near identical to PNG. Basically, it's no compression, besides going down to 8-bit. When discussing black and white comics, this results in no difference at all. It'd be possible to see differences on tonally complex black and white drawings, and on variously dithered black and white images.
Concerning dithering and display of BW images on eink screens things become more complex. First you have screens that are extremely low bit. Software of the devices dithers everything that's over that level on it's own, to various result. To get the best results, it's best to dither an image beforehand manually. It's more creative, and offers higher levels of customization of the output. My process of converting photos for e-ink screensavers and covers involves converting them to BW, adjusting contrasts, then dithering them via Ximagic pluging in Photoshop at very low levels. I always save them in at 100% jpeg, just to be sure.
With that in mind we come to this:
Quote:
Originally Posted by innocenat
It's true that adding dithering will result in worse compression in JPEG
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Dithering and high Jpeg compression indeed is bad. At least for more complex images. It mashes dithered look with jpeg compression artefacts, and can cause ruinous results. PNG is a sure solution, but high quality jpeg output is just as effective.