Add WebP image format support (Bug#51296)

* configure.ac (--with-webp): New option.
(HAVE_WEBP): New variable.
(emacs_config_features): Add webp.
* src/image.c (enum webp_keyword_index) [HAVE_WEBP]: New enum.
(webp_format) [HAVE_WEBP]: New variable.
(webp_image_p, init_webp_functions, webp_load) [HAVE_WEBP]: New
functions for WebP support.
(image_types) [HAVE_WEBP]: Define WebP format.
(syms_of_image) <Qwebp> [HAVE_WEBP]: New DEFSYM.  Add image type Qwebp.
* src/Makefile.in (LIBIMAGE): Add WEBP_LIBS.

* lisp/files.el (auto-mode-alist):
* lisp/image-file.el (image-file-name-extensions):
* lisp/image.el (image-type-header-regexps)
(image-type-file-name-regexps, image-type-auto-detectable): Add WebP
support.
* lisp/term/w32-win.el (dynamic-library-alist): Add the libwebp DLL.

* INSTALL:
* admin/CPP-DEFINES:
* doc/lispref/display.texi (Image Formats, Other Image Types):
* nt/INSTALL: Document WebP support.

* test/lisp/image-tests.el (image-find-image)
(image-type-from-file-name): Expand tests.
* test/src/image-tests.el (image-tests--files): Add WebP.
(image-tests-image-size/webp, image-tests-image-mask-p/webp)
(image-tests-image-metadata/webp): New tests.
* test/data/image/black.webp: New file.

1 files changed, 21 insertions, 2 deletions

diff --git a/test/src/image-tests.el b/test/src/image-tests.el
index d5e3a7cc5ca..b921739a056 100644
--- a/test/src/image-tests.el
+++ b/test/src/image-tests.el
@@ -44,6 +44,8 @@
     (tiff . ,(expand-file-name
               "nextstep/GNUstep/Emacs.base/Resources/emacs.tiff"
               source-directory))
+    (webp . ,(expand-file-name "test/data/image/black.webp"
+                               source-directory))
     (xbm . ,(find-image '((:file "gnus/gnus.xbm" :type xbm))))
     (xpm . ,(find-image '((:file "splash.xpm" :type xpm))))
     ;; TODO: gif
@@ -86,6 +88,13 @@
      (should (floatp a))
      (should (floatp b)))))
 
+(ert-deftest image-tests-image-size/webp ()
+  (image-skip-unless 'webp)
+  (pcase (image-size (create-image (cdr (assq 'webp image-tests--files))))
+    (`(,a . ,b)
+     (should (floatp a))
+     (should (floatp b)))))
+
 (ert-deftest image-tests-image-size/xbm ()
   (image-skip-unless 'xbm)
   (pcase (image-size (cdr (assq 'xbm image-tests--files)))
@@ -130,7 +139,12 @@
 (ert-deftest image-tests-image-mask-p/tiff ()
   (image-skip-unless 'tiff)
   (should-not (image-mask-p (create-image
-                             (cdr (assq 'tiff image-tests--files))))))
+                             (cdr (assq 'tiff image-tests--files))))))
+
+(ert-deftest image-tests-image-mask-p/webp ()
+  (image-skip-unless 'webp)
+  (should-not (image-mask-p (create-image
+                             (cdr (assq 'webp image-tests--files))))))
 
 (ert-deftest image-tests-image-mask-p/xbm ()
   (image-skip-unless 'xbm)
@@ -173,7 +187,12 @@
 (ert-deftest image-tests-image-metadata/tiff ()
   (image-skip-unless 'tiff)
   (should-not (image-metadata
-               (create-image (cdr (assq 'tiff image-tests--files))))))
+               (create-image (cdr (assq 'tiff image-tests--files))))))
+
+(ert-deftest image-tests-image-metadata/webp ()
+  (image-skip-unless 'webp)
+  (should-not (image-metadata
+               (create-image (cdr (assq 'webp image-tests--files))))))
 
 (ert-deftest image-tests-image-metadata/xbm ()
   (image-skip-unless 'xbm)