Mailinglist Archive: opensuse (958 mails)

< Previous Next >
[opensuse] Re: pngquant - PNG compressor
On 5/3/2019 2:07 PM, Carlos E. R. wrote:
216845 Screenshot_original.png
213845 Screenshot_2019-05-03_13-57-51-copy.png optipng

90144 Screenshot_2019-05-03_13-57-51-copy-2-fs8.png <===quant

I'm not very impressed ;-)
Now I'm impressed.


Trying pngquant from the graphics repo, as there is no 15.1 version on
David's repo:

cer@Elesar:~/Pictures/Screenshots> cp Screenshot_2019-05-03_13-57-51.png
Screenshot_2019-05-03_13-57-51-copy-2.png
cer@Elesar:~/Pictures/Screenshots> pngquant
Screenshot_2019-05-03_13-57-51-copy-2.png
cer@Elesar:~/Pictures/Screenshots> l
total 948
drwxr-xr-x 2 cer users 4096 May 3 23:01 ./
drwxr-xr-x 5 cer users 4096 Apr 21 14:53 ../
-rw-r--r-- 1 cer users 90144 May 3 23:01
Screenshot_2019-05-03_13-57-51-copy-2-fs8.png <===
-rw-r--r-- 1 cer users 216845 May 3 23:01
Screenshot_2019-05-03_13-57-51-copy-2.png
-rw-r--r-- 1 cer users 213845 May 3 22:54
Screenshot_2019-05-03_13-57-51-copy.png
-rw-r--r-- 1 cer users 216845 May 3 22:54
Screenshot_2019-05-03_13-57-51-copy.png.bak
-rw-r--r-- 1 cer users 216845 May 3 13:58 Screenshot_2019-05-03_13-57-51.png
cer@Elesar:~/Pictures/Screenshots>




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).

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.


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.

Still, if the picture you encoded really had only 256 colors, I've
seen png files compress alot better with low-detail pictures.


--
To unsubscribe, e-mail: opensuse+unsubscribe@xxxxxxxxxxxx
To contact the owner, e-mail: opensuse+owner@xxxxxxxxxxxx

< Previous Next >
Follow Ups