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, 281 insertions, 0 deletions

diff --git a/src/image.c b/src/image.c
index ff05741b2cd..fe0bb509c58 100644
--- a/src/image.c
+++ b/src/image.c
@@ -8739,8 +8739,280 @@ gif_load (struct frame *f, struct image *img)
 #endif /* HAVE_GIF */
 
 
+#ifdef HAVE_WEBP
+
+
+/***********************************************************************
+				 WebP
+ ***********************************************************************/
+
+#include "webp/decode.h"
+
+/* Indices of image specification fields in webp_format, below.  */
+
+enum webp_keyword_index
+{
+  WEBP_TYPE,
+  WEBP_DATA,
+  WEBP_FILE,
+  WEBP_ASCENT,
+  WEBP_MARGIN,
+  WEBP_RELIEF,
+  WEBP_ALGORITHM,
+  WEBP_HEURISTIC_MASK,
+  WEBP_MASK,
+  WEBP_BACKGROUND,
+  WEBP_LAST
+};
+
+/* Vector of image_keyword structures describing the format
+   of valid user-defined image specifications.  */
+
+static const struct image_keyword webp_format[WEBP_LAST] =
+{
+  {":type",		IMAGE_SYMBOL_VALUE,			1},
+  {":data",		IMAGE_STRING_VALUE,			0},
+  {":file",		IMAGE_STRING_VALUE,			0},
+  {":ascent",		IMAGE_ASCENT_VALUE,			0},
+  {":margin",		IMAGE_NON_NEGATIVE_INTEGER_VALUE_OR_PAIR, 0},
+  {":relief",		IMAGE_INTEGER_VALUE,			0},
+  {":conversion",	IMAGE_DONT_CHECK_VALUE_TYPE,		0},
+  {":heuristic-mask",	IMAGE_DONT_CHECK_VALUE_TYPE,		0},
+  {":mask",		IMAGE_DONT_CHECK_VALUE_TYPE,		0},
+  {":background",	IMAGE_STRING_OR_NIL_VALUE,		0}
+};
+
+/* Return true if OBJECT is a valid WebP image specification.  */
+
+static bool
+webp_image_p (Lisp_Object object)
+{
+  struct image_keyword fmt[WEBP_LAST];
+  memcpy (fmt, webp_format, sizeof fmt);
+
+  if (!parse_image_spec (object, fmt, WEBP_LAST, Qwebp))
+    return false;
+
+  /* Must specify either the :data or :file keyword.  */
+  return fmt[WEBP_FILE].count + fmt[WEBP_DATA].count == 1;
+}
+
+#ifdef WINDOWSNT
+
+/* WebP library details.  */
+
+DEF_DLL_FN (int, WebPGetInfo, (const uint8_t *, size_t, int *, int *));
+DEF_DLL_FN (VP8StatusCode, WebPGetFeatures, (const uint8_t *, size_t, WebPBitstreamFeatures *));
+DEF_DLL_FN (uint8_t *, WebPDecodeRGB, (const uint8_t *, size_t, int *, int *));
+DEF_DLL_FN (uint8_t *, WebPDecodeBGR, (const uint8_t *, size_t, int *, int *));
+DEF_DLL_FN (void, WebPFreeDecBuffer (WebPDecBuffer *));
+
+static bool
+init_webp_functions (void)
+{
+  HMODULE library;
+
+  if (!(library = w32_delayed_load (Qwebp)))
+    return false;
+
+  LOAD_DLL_FN (library, WebPGetInfo);
+  LOAD_DLL_FN (library, WebPGetFeatures);
+  LOAD_DLL_FN (library, WebPDecodeRGBA);
+  LOAD_DLL_FN (library, WebPDecodeRGB);
+  LOAD_DLL_FN (library, WebPFree);
+  return true;
+}
+
+#undef WebPGetInfo
+#undef WebPGetFeatures
+#undef WebPDecodeRGBA
+#undef WebPDecodeRGB
+#undef WebPFree
+
+#define WebPGetInfo fn_WebPGetInfo
+#define WebPGetFeatures fn_WebPGetFeatures
+#define WebPDecodeRGBA fn_WebPDecodeRGBA
+#define WebPDecodeRGB fn_WebPDecodeRGB
+#define WebPFree fn_WebPFree
+
+#endif /* WINDOWSNT */
+
+/* Load WebP image IMG for use on frame F.  Value is true if
+   successful.  */
+
+static bool
+webp_load (struct frame *f, struct image *img)
+{
+  ptrdiff_t size = 0;
+  uint8_t *contents;
+  Lisp_Object file;
+
+  /* Open the WebP file.  */
+  Lisp_Object specified_file = image_spec_value (img->spec, QCfile, NULL);
+  Lisp_Object specified_data = image_spec_value (img->spec, QCdata, NULL);
+
+  if (NILP (specified_data))
+    {
+      int fd;
+      file = image_find_image_fd (specified_file, &fd);
+      if (!STRINGP (file))
+	{
+	  image_error ("Cannot find image file `%s'", specified_file);
+	  return false;
+	}
+
+      contents = (uint8_t *) slurp_file (fd, &size);
+      if (contents == NULL)
+	{
+	  image_error ("Error loading WebP image `%s'", file);
+	  return false;
+	}
+    }
+  else
+    {
+      if (!STRINGP (specified_data))
+	{
+	  image_error ("Invalid image data `%s'", specified_data);
+	  return false;
+	}
+      contents = SDATA (specified_data);
+      size = SBYTES (specified_data);
+    }
+
+  /* Validate the WebP image header.  */
+  if (!WebPGetInfo (contents, size, NULL, NULL))
+    {
+      if (!NILP (specified_data))
+	image_error ("Not a WebP file: `%s'", file);
+      else
+	image_error ("Invalid header in WebP image data");
+      goto webp_error1;
+    }
+
+  /* Get WebP features.  */
+  WebPBitstreamFeatures features;
+  VP8StatusCode result = WebPGetFeatures (contents, size, &features);
+  switch (result)
+    {
+    case VP8_STATUS_OK:
+      break;
+    case VP8_STATUS_NOT_ENOUGH_DATA:
+    case VP8_STATUS_OUT_OF_MEMORY:
+    case VP8_STATUS_INVALID_PARAM:
+    case VP8_STATUS_BITSTREAM_ERROR:
+    case VP8_STATUS_UNSUPPORTED_FEATURE:
+    case VP8_STATUS_SUSPENDED:
+    case VP8_STATUS_USER_ABORT:
+    default:
+      /* Error out in all other cases.  */
+      if (!NILP (specified_data))
+	image_error ("Error when interpreting WebP image data: `%s'", file);
+      else
+	image_error ("Error when interpreting WebP image data");
+      goto webp_error1;
+    }
+
+  /* Decode WebP data.  */
+  uint8_t *decoded;
+  int width, height;
+  if (features.has_alpha)
+    /* Linear [r0, g0, b0, a0, r1, g1, b1, a1, ...] order.  */
+    decoded = WebPDecodeRGBA (contents, size, &width, &height);
+  else
+    /* Linear [r0, g0, b0, r1, g1, b1, ...] order.  */
+    decoded = WebPDecodeRGB (contents, size, &width, &height);
+
+  if (!(width <= INT_MAX && height <= INT_MAX
+	&& check_image_size (f, width, height)))
+    {
+      image_size_error ();
+      goto webp_error2;
+    }
+
+  /* Create the x image and pixmap.  */
+  Emacs_Pix_Container ximg, mask_img;
+  if (!image_create_x_image_and_pixmap (f, img, width, height, 0, &ximg, false))
+    goto webp_error2;
+
+  /* Create an image and pixmap serving as mask if the WebP image
+     contains an alpha channel.  */
+  if (features.has_alpha
+      && !image_create_x_image_and_pixmap (f, img, width, height, 1, &mask_img, true))
+    {
+      image_destroy_x_image (ximg);
+      image_clear_image_1 (f, img, CLEAR_IMAGE_PIXMAP);
+      goto webp_error2;
+    }
+
+  /* Fill the X image and mask from WebP data.  */
+  init_color_table ();
+
+  uint8_t *p = decoded;
+  for (int y = 0; y < height; ++y)
+    {
+      for (int x = 0; x < width; ++x)
+	{
+	  int r = *p++ << 8;
+	  int g = *p++ << 8;
+	  int b = *p++ << 8;
+	  PUT_PIXEL (ximg, x, y, lookup_rgb_color (f, r, g, b));
+
+	  /* An alpha channel associates variable transparency with an
+	     image.  WebP allows up to 256 levels of partial transparency.
+	     We handle this like with PNG (which see), using the frame's
+	     background color to combine the image with.  */
+	  if (features.has_alpha)
+	    {
+	      if (mask_img)
+		PUT_PIXEL (mask_img, x, y, *p > 0 ? PIX_MASK_DRAW : PIX_MASK_RETAIN);
+	      ++p;
+	    }
+	}
+    }
+
+#ifdef COLOR_TABLE_SUPPORT
+  /* Remember colors allocated for this image.  */
+  img->colors = colors_in_color_table (&img->ncolors);
+  free_color_table ();
+#endif /* COLOR_TABLE_SUPPORT */
+
+  /* Put ximg into the image.  */
+  image_put_x_image (f, img, ximg, 0);
+
+  /* Same for the mask.  */
+  if (mask_img)
+    {
+      /* Fill in the background_transparent field while we have the
+	 mask handy.  Casting avoids a GCC warning.  */
+      image_background_transparent (img, f, (Emacs_Pix_Context)mask_img);
+
+      image_put_x_image (f, img, mask_img, 1);
+    }
+
+  img->width = width;
+  img->height = height;
+
+  /* Clean up.  */
+  WebPFree (decoded);
+  if (NILP (specified_data))
+    xfree (contents);
+  return true;
+
+ webp_error2:
+  WebPFree (decoded);
+
+ webp_error1:
+  if (NILP (specified_data))
+    xfree (contents);
+  return false;
+}
+
+#endif /* HAVE_WEBP */
+
+
 #ifdef HAVE_IMAGEMAGICK
 
+
 /***********************************************************************
 				 ImageMagick
 ***********************************************************************/
@@ -10726,6 +10998,10 @@ static struct image_type const image_types[] =
  { SYMBOL_INDEX (Qxpm), xpm_image_p, xpm_load, image_clear_image,
    IMAGE_TYPE_INIT (init_xpm_functions) },
 #endif
+#if defined HAVE_WEBP
+ { SYMBOL_INDEX (Qwebp), webp_image_p, webp_load, image_clear_image,
+   IMAGE_TYPE_INIT (init_webp_functions) },
+#endif
  { SYMBOL_INDEX (Qxbm), xbm_image_p, xbm_load, image_clear_image },
  { SYMBOL_INDEX (Qpbm), pbm_image_p, pbm_load, image_clear_image },
 };
@@ -10891,6 +11167,11 @@ non-numeric, there is no explicit limit on the size of images.  */);
   add_image_type (Qpng);
 #endif
 
+#if defined (HAVE_WEBP)
+  DEFSYM (Qwebp, "webp");
+  add_image_type (Qwebp);
+#endif
+
 #if defined (HAVE_IMAGEMAGICK)
   DEFSYM (Qimagemagick, "imagemagick");
   add_image_type (Qimagemagick);