On 04/05/2019 07.56, L A Walsh wrote:
On 5/3/2019 2:07 PM, Carlos E. R. wrote:
And the result is pretty good for sending informative screenshots.
However, all of them seem to be 8 bit, according to "file":
cer@Elesar:~/Pictures/Screenshots> file *png
...run through extraneous info deletion...amazing what you can do if you go for the lossy option:
PNG, 8-bit/color RGB, non-interlaced <-- original PNG, 8-bit colormap, non-interlaced <-- pngquant PNG, 8-bit/color RGB, non-interlaced <-- optipng
I suspect you would get similar results if you did a conversion to GIF format as that's essentially what it appears to be doing.
I.e. an 8-bit colormap = 256-color image vs. 24-bit colormap with 2**24 (4 mega colors).
What about 16 bit colors?
For the stated purpose of a color limited screenshot, pngquant is clearly superior, however it would be nice if we knew if it was losing color information or not -- i.e. if there really are no colors that are dropped, approximated or dithered, then you have an accurate reproduction at a smaller size and that's cool!
But it if throws away info and doesn't tell you, color me less than impressed.
Yes, that's a point.
On the otherhand -- people lived with GIF's and 256-bit color for several years back in the late 80's, early 90's...wasn't until VRAM got cheap enough for 24-bit color that interest faded for most applications.
And less. I had occasion to test some astronomical photograph samples that came with a CCD camera for a telescope (it was cooled with peltzier cells, around 1990, B&W. The software came in basic, so I analyzed it, and started doing an equivalent in turbo pascal. A problem was that the VGA (SVGA?) displays of that the time could not display 256 levels of gray (or any single colour), just 64 (with a color map). So what it did was create variations adding a bit of blue, red or yellow to change the light value of the pixel, thus "emulating" 256 levels of gray. Even so, it did "impressive" manipulation of the photos. Altering the rendition curve, for instance, hidden important details appeared on the photo (taking a minute). Of course, tools like gimp can do that now in "really" impressive manner and in a second on a big photo.
Still, if the picture you encoded really had only 256 colors, I've seen png files compress alot better with low-detail pictures.
Yep. -- Cheers / Saludos, Carlos E. R. (from openSUSE, Leap 15.1 x86_64 (ssd-test)) -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org