WebP images with alpha channel renders in poor quality in the Emacs.
See http://lgarc.narod.ru/pics/emacs-webp-poor-quality.png

If I convert webp image to png, quality is ok in resulting image.  Also, if
I add webp as native image under MacOS (requires Emacs patch) then quality
is also ok.

Looks like partial transparency is incorrectly applied for webp images.

Thanks

In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.20, cairo version 1.16.0) of 2022-10-25 built on x1
Repository revision: 9bfe00dda6b59d9b93eb7a825f6e0868afa1cca3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12009000
System Description: Ubuntu 20.04.1 LTS

Configured using:
 'configure --with-modules'

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LIBSELINUX LIBXML2 MODULES NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND
SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS WEBP X11 XDBE XIM XINPUT2 XPM
GTK3 ZLIB

Important settings:
  value of $LC_MONETARY: ru_RU.UTF-8
  value of $LC_NUMERIC: ru_RU.UTF-8
  value of $LC_TIME: ru_RU.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: ◁Chat

Minor modes in effect:
  tracking-mode: t
  telega-adblock-mode: t
  global-telega-mnz-mode: t
  telega-mnz-mode: t
  global-telega-url-shorten-mode: t
  telega-url-shorten-mode: t
  telega-stories-mode: t
  telega-root-auto-fill-mode: t
  telega-recognize-voice-message-mode: t
  telega-active-locations-mode: t
  telega-my-location-mode: t
  telega-patrons-mode: t
  global-telega-squash-message-mode: t
  telega-autoplay-mode: t
  telega-appindicator-mode: t
  telega-mode-line-mode: t
  telega-notifications-mode: t
  cursor-sensor-mode: t
  cursor-intangible-mode: t
  reverse-im-mode: t
  mlscroll-mode: t
  desktop-save-mode: t
  company-mode: t
  pyvenv-mode: t
  which-function-mode: t
  shell-dirtrack-mode: t
  global-paren-face-mode: t
  save-place-mode: t
  display-time-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  icomplete-mode: t
  disable-mouse-global-mode: t
  override-global-mode: t
  global-eldoc-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
/home/lg/.emacs.d/elpa/magit-20210327.1617/magit-section hides
/home/lg/.emacs.d/elpa/magit-section-20210702.822/magit-section
~/dev/emacs-libvterm/vterm hides
/home/lg/.emacs.d/elpa/vterm-20210326.1458/vterm
/home/lg/.emacs.d/elpa/transient-20210315.1902/transient hides
/usr/local/share/emacs/29.0.50/lisp/transient

Features:
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vterm bookmark face-remap term disp-table ehelp vterm-module term/xterm
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telega-url-shorten telega-stories telega-dashboard telega-live-location
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generate-lisp-file url-domsuf url-util mailcap url-handlers url-parse
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lisp-float-type elisp-mode mwheel term/x-win x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer nadvice seq
simple cl-generic indonesian philippine cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
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cyrillic chinese composite emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button
loaddefs theme-loaddefs faces cus-face macroexp files window
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget keymap hashtable-print-readable backquote threads dbusbind
inotify dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit xinput2 x multi-tty make-network-process
emacs)

Memory information:
((conses 16 6192449 1055030)
 (symbols 48 58618 3)
 (strings 32 883577 49058)
 (string-bytes 1 23200329)
 (vectors 16 308140)
 (vector-slots 8 3071505 351145)
 (floats 8 562338 2818)
 (intervals 56 305793 15205)
 (buffers 1000 131))

-- 
lg