Re: libwebp and YUV sharpness

On Fri, 2 Apr 2021, Shane Bishop wrote:

> Hi folks,
> We use the gmagick extension (2.0.5rc1/1.3.35) for PHP (7.3) to produce
> WebP images for our client sites, and we're wondering if there is a way to
> pass the use_sharp_yuv to libwebp (1.2.0) via gmagick?
> We have a particular client who has done some testing with cwebp and the
> -sharp-yuv option and they are pleased with the results, but gmagick is
> currently yielding "softer" results than they like.
> Any ideas on this?

GraphicsMagick supports a bunch of WebP defines.  There is a define 
called 'webp:use-sharp-yuv' which may be set to the values 'true' or 
'false'.  Hopefully the gmagick extension supports passing 'define' 
options for the reader and writer.

> Also, somewhat related, I'm noticing that gmagick.so seems to be linked to
> both libwebp.so.6 (system-installed) and libwebp.so.7 (version 1.2.0 that
> we install from source). Does gmagick automatically use the newer one if
> available? Or how do we know which one is in use?

That does not sound good.  If using Linux, one can enable run-time 
linker debugging via the LD_DEBUG environment variable and then run 
your program.  Debug output should appear on the terminal.  This is 
documented in the ld.so manual page.  For example, you could specify 
'LD_DEBUG=symbols' or 'LD_DEBUG=libs'.  This is way to know the 
symbols used and the 
libraries searched.

Bob
-- 
Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
Public Key,     http://www.simplesystems.org/users/bfriesen/public-key.txt