Implement :max-width/:max-height for (ImageMagic) images

* doc/lispref/display.texi (ImageMagick Images): Mention :max-width and
:max-height.

* lisp/net/shr.el (shr-rescale-image): Use the new
:max-width/:max-height functionality.

* src/image.c (compute_image_size): New function to implement
:max-width and :max-height.
(imagemagick_load_image): Use it.

7 files changed, 121 insertions, 45 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index c00d3392908..e95010a11a9 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,8 @@
+2013-06-23  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+        * display.texi (ImageMagick Images): Mention :max-width and
+        :max-height.
+
 2013-06-20  Paul Eggert  <eggert@cs.ucla.edu>
 
         * numbers.texi (Math Functions): Remove obsolete function log10.
diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 34eda6ecd6f..d82b9a4c5a2 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -4653,6 +4653,15 @@ image.  If only one of them is specified, the other one will be
 calculated so as to preserve the aspect ratio.  If both are specified,
 aspect ratio may not be preserved.
 
+@item :max-width, :max-height
+The @code{:max-width} and @code{:max-height} keywords are used for
+scaling if the size of the image of the image exceeds these values.
+If @code{:width} is set it will have presedence over @code{max-width},
+and if @code{:height} is set it will have presedence over
+@code{max-height}, but you can otherwise mix these keywords as you
+wish.  @code{:max-width} and @code{:max-height} will always preserve
+the aspec ratio.
+
 @item :rotation
 Specifies a rotation angle in degrees.
 
diff --git a/etc/NEWS b/etc/NEWS
index 475b4b26fdb..d7364542ce1 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -695,6 +695,9 @@ ImageMagick types are treated as images.  The function
 `imagemagick-filter-types' returns the list of types that will be
 treated as images.
 
+*** ImageMagick images now support the :max-width and :max-height
+keywords.
+
 ** Minibuffer
 
 *** In minibuffer filename prompts, `C-M-f' and `C-M-b' now move to the
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index a3fc6bd172f..ff41129b906 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2013-06-23  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+        * net/shr.el (shr-rescale-image): Use the new
+        :max-width/:max-height functionality.
+
 2013-06-23  Ivan Kanis  <ivan@kanis.fr>
 
         * net/eww.el (eww-search-prefix): New variable.
diff --git a/lisp/net/shr.el b/lisp/net/shr.el
index 868956d3e21..979743f9588 100644
--- a/lisp/net/shr.el
+++ b/lisp/net/shr.el
@@ -741,34 +741,18 @@ size, and full-buffer size."
 (defun shr-rescale-image (data &optional force)
   "Rescale DATA, if too big, to fit the current buffer.
 If FORCE, rescale the image anyway."
-  (let ((image (create-image data nil t :ascent 100)))
-    (if (or (not (fboundp 'imagemagick-types))
-            (not (get-buffer-window (current-buffer))))
-        image
-      (let* ((size (image-size image t))
-             (width (car size))
-             (height (cdr size))
-             (edges (window-inside-pixel-edges
-                     (get-buffer-window (current-buffer))))
-             (window-width (truncate (* shr-max-image-proportion
-                                        (- (nth 2 edges) (nth 0 edges)))))
-             (window-height (truncate (* shr-max-image-proportion
-                                         (- (nth 3 edges) (nth 1 edges)))))
-             scaled-image)
-        (when (or force
-                  (> height window-height))
-          (setq image (or (create-image data 'imagemagick t
-                                        :height window-height
-                                        :ascent 100)
-                          image))
-          (setq size (image-size image t)))
-        (when (> (car size) window-width)
-          (setq image (or
-                       (create-image data 'imagemagick t
-                                     :width window-width
-                                     :ascent 100)
-                       image)))
-        image))))
+  (if (or (not (fboundp 'imagemagick-types))
+          (not (get-buffer-window (current-buffer))))
+      (create-image data nil t :ascent 100)
+    (let ((edges (window-inside-pixel-edges
+                  (get-buffer-window (current-buffer)))))
+      (create-image
+       data 'imagemagick t
+       :ascent 100
+       :max-width (truncate (* shr-max-image-proportion
+                               (- (nth 2 edges) (nth 0 edges))))
+       :max-height (truncate (* shr-max-image-proportion
+                                (- (nth 3 edges) (nth 1 edges))))))))
 
 ;; url-cache-extract autoloads url-cache.
 (declare-function url-cache-create-filename "url-cache" (url))
diff --git a/src/ChangeLog b/src/ChangeLog
index b2773ddbf50..f9451711f32 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2013-06-23  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+        * image.c (compute_image_size): New function to implement
+        :max-width and :max-height.
+        (imagemagick_load_image): Use it.
+
 2013-06-23  Paul Eggert  <eggert@cs.ucla.edu>
 
         Try to avoid malloc SEGVs on Cygwin (Bug#14569).
diff --git a/src/image.c b/src/image.c
index ffb3cd15e93..b65ee7df789 100644
--- a/src/image.c
+++ b/src/image.c
@@ -132,6 +132,8 @@ static void free_color_table (void);
 static unsigned long *colors_in_color_table (int *n);
 #endif
 
+Lisp_Object QCmax_width, QCmax_height;
+
 /* Code to deal with bitmaps.  Bitmaps are referenced by their bitmap
    id, which is just an int that this section returns.  Bitmaps are
    reference counted so they can be shared among frames.
@@ -7489,6 +7491,76 @@ gif_load (struct frame *f, struct image *img)
 #endif /* HAVE_GIF */
 
 
+static void
+compute_image_size (size_t width, size_t height,
+                    Lisp_Object spec,
+                    int *d_width, int *d_height)
+{
+  Lisp_Object value;
+  int desired_width, desired_height;
+
+  /* If width and/or height is set in the display spec assume we want
+     to scale to those values.  If either h or w is unspecified, the
+     unspecified should be calculated from the specified to preserve
+     aspect ratio.  */
+  value = image_spec_value (spec, QCwidth, NULL);
+  desired_width = (INTEGERP (value)  ? XFASTINT (value) : -1);
+  value = image_spec_value (spec, QCheight, NULL);
+  desired_height = (INTEGERP (value) ? XFASTINT (value) : -1);
+
+  if (desired_width == -1)
+    {
+      value = image_spec_value (spec, QCmax_width, NULL);
+      if (INTEGERP (value) &&
+          width > XFASTINT (value))
+        {
+          /* The image is wider than :max-width. */
+          desired_width = XFASTINT (value);
+          if (desired_height == -1)
+            {
+              value = image_spec_value (spec, QCmax_height, NULL);
+              if (INTEGERP (value))
+                {
+                  /* We have no specified height, but we have a
+                     :max-height value, so check that we satisfy both
+                     conditions. */
+                  desired_height = (double) desired_width / width * height;
+                  if (desired_height > XFASTINT (value))
+                    {
+                      desired_height = XFASTINT (value);
+                      desired_width = (double) desired_height / height * width;
+                    }
+                }
+              else
+                {
+                  /* We have no specified height and no specified
+                     max-height, so just compute the height. */
+                  desired_height = (double) desired_width / width * height;
+                }
+            }
+        }
+    }
+
+  if (desired_height == -1)
+    {
+      value = image_spec_value (spec, QCmax_height, NULL);
+      if (INTEGERP (value) &&
+          height > XFASTINT (value))
+          desired_height = XFASTINT (value);
+    }
+
+  if (desired_width != -1 && desired_height == -1)
+    /* w known, calculate h.  */
+    desired_height = (double) desired_width / width * height;
+
+  if (desired_width == -1 && desired_height != -1)
+    /* h known, calculate w.  */
+    desired_width = (double) desired_height / height * width;
+
+  *d_width = desired_width;
+  *d_height = desired_height;
+}
+
 /***********************************************************************
                                  ImageMagick
 ***********************************************************************/
@@ -7516,6 +7588,8 @@ enum imagemagick_keyword_index
     IMAGEMAGICK_BACKGROUND,
     IMAGEMAGICK_HEIGHT,
     IMAGEMAGICK_WIDTH,
+    IMAGEMAGICK_MAX_HEIGHT,
+    IMAGEMAGICK_MAX_WIDTH,
     IMAGEMAGICK_ROTATION,
     IMAGEMAGICK_CROP,
     IMAGEMAGICK_LAST
@@ -7538,6 +7612,8 @@ static struct image_keyword imagemagick_format[IMAGEMAGICK_LAST] =
     {":background",     IMAGE_STRING_OR_NIL_VALUE,              0},
     {":height",         IMAGE_INTEGER_VALUE,                    0},
     {":width",          IMAGE_INTEGER_VALUE,                    0},
+    {":max-height",     IMAGE_INTEGER_VALUE,                    0},
+    {":max-width",      IMAGE_INTEGER_VALUE,                    0},
     {":rotation",       IMAGE_NUMBER_VALUE,                     0},
     {":crop",           IMAGE_DONT_CHECK_VALUE_TYPE,            0}
   };
@@ -7726,24 +7802,10 @@ imagemagick_load_image (struct frame *f, struct image *img,
     PixelSetBlue  (bg_wand, (double) bgcolor.blue  / 65535);
   }
 
-  /* If width and/or height is set in the display spec assume we want
-     to scale to those values.  If either h or w is unspecified, the
-     unspecified should be calculated from the specified to preserve
-     aspect ratio.  */
-  value = image_spec_value (img->spec, QCwidth, NULL);
-  desired_width = (INTEGERP (value)  ? XFASTINT (value) : -1);
-  value = image_spec_value (img->spec, QCheight, NULL);
-  desired_height = (INTEGERP (value) ? XFASTINT (value) : -1);
-
-  height = MagickGetImageHeight (image_wand);
-  width = MagickGetImageWidth (image_wand);
+  compute_image_size (MagickGetImageWidth (image_wand),
+                      MagickGetImageHeight (image_wand),
+                      img->spec, &desired_width, &desired_height);
 
-  if (desired_width != -1 && desired_height == -1)
-    /* w known, calculate h.  */
-    desired_height = (double) desired_width / width * height;
-  if (desired_width == -1 && desired_height != -1)
-    /* h known, calculate w.  */
-    desired_width = (double) desired_height / height * width;
   if (desired_width != -1 && desired_height != -1)
     {
       status = MagickScaleImage (image_wand, desired_width, desired_height);
@@ -8895,6 +8957,8 @@ non-numeric, there is no explicit limit on the size of images.  */);
   DEFSYM (Qheuristic, "heuristic");
 
   DEFSYM (Qpostscript, "postscript");
+  DEFSYM (QCmax_width, ":max-width");
+  DEFSYM (QCmax_height, ":max-height");
 #ifdef HAVE_GHOSTSCRIPT
   ADD_IMAGE_TYPE (Qpostscript);
   DEFSYM (QCloader, ":loader");