[PATCH] Feature proposal : support "scale=" includegraphics option in the builtin latex exporter.

[Emmanuel Charpentier <emm.charpentier@free.fr>]

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Attached is my proposal for the feature I suggested. My quick tests
pass[1]. Better tests by someone knowledgeable in graphics would be 
useful, as well as a test in the test suite.

HTH,

--
Emmanuel Charpentier

[1] I get unrelated failures from "make test" :
4 unexpected results:
   FAILED  test-org-clock/clocktable/extend-today-until
   FAILED  test-org-clock/clocktable/step
   FAILED  test-org/timestamp-from-string
   FAILED  test-org/timestamp-from-time

I can't see any link with my proposal. BTW, I get the same failures
from the unmodified master branch (fetched this morning...).

Le vendredi 19 avril 2019 à 09:27 +0200, Emmanuel Charpentier a écrit :
> Dear list,
> 
> Most graphics-able exporters support some form of a scale parameter,
> sizing the resultant image as a function of the original graphics
> file
> (intended) size.
> 
> This is true for:
>   * built-in ODT exporter
>   * ox-pandoc Latex/ODT/DOCX exporters.
> 
> This possibility comes handy to avoid (or at least master) the side
> effects of scaling (fonts amplification, /reduction, bitmap
> fuzinness,
> etc...).
> 
> It should be supported on the native LaTeX exporter (and possibly
> "scale: 1" may become the default...).
> 
> In addition (but this is probably a different problem), some
> scaling/sizing mechanism may be implemented for the HTML exporter.
> 
> --
> Emmanuel Charpentier
> 

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From 2526a06e4f77a2fdae615a95365f557c40b6d968 Mon Sep 17 00:00:00 2001
From: Emmanuel Charpentier <emm.charpentier@free.fr>
Date: Sat, 20 Apr 2019 10:25:24 +0200
Subject: [PATCH] Support a :scale parameter in org-latex-export-to-latex and
 friends

* lisp/ox-latex.el: introduce a :scale #+ATTR_LATEX parameter, as well
as a "" default value for it.  When present, it overrides :width and
:height parameters (as it does for ODT export and in ox-pandoc
exporters) ; therefore, setting a default value for :scale should be
exceptional.

Implementation: uses \scalebox for tikz/pgf images, "scale=" parameter
of \includegraphics in other cases.

* doc/org-manual.org: document the new :scale #+ATTR_LATEX parameter,
---
 doc/org-manual.org |  8 ++++++--
 lisp/ox-latex.el   | 49 ++++++++++++++++++++++++++++++++++------------
 2 files changed, 42 insertions(+), 15 deletions(-)

diff --git a/doc/org-manual.org b/doc/org-manual.org
index a8f4a45ea..a9114184a 100644
--- a/doc/org-manual.org
+++ b/doc/org-manual.org
@@ -13277,14 +13277,18 @@ insert the image.  But for TikZ (http://sourceforge.net/projects/pgf/)
 images, the back-end uses an ~\input~ macro wrapped within
 a ~tikzpicture~ environment.
 
-For specifying image =:width=, =:height=, and other =:options=, use
-this syntax:
+For specifying image =:width=, =:height=, =:scale= and other =:options=,
+use this syntax:
 
 #+begin_example
 ,#+ATTR_LATEX: :width 5cm :options angle=90
 [[./img/sed-hr4049.pdf]]
 #+end_example
 
+A =:scale= parameter overrides both =:width= and =:height= parameters ;
+therefore, setting its default value should be done only in exceptional
+circumstances.
+
 For custom commands for captions, use the =:caption= attribute.  It
 overrides the default =#+CAPTION= value:
 
diff --git a/lisp/ox-latex.el b/lisp/ox-latex.el
index cdcb07aca..60b8773b0 100644
--- a/lisp/ox-latex.el
+++ b/lisp/ox-latex.el
@@ -127,6 +127,7 @@
     (:latex-format-headline-function nil nil org-latex-format-headline-function)
     (:latex-format-inlinetask-function nil nil org-latex-format-inlinetask-function)
     (:latex-hyperref-template nil nil org-latex-hyperref-template t)
+    (:latex-image-default-scale nil nil org-latex-image-default-scale)
     (:latex-image-default-height nil nil org-latex-image-default-height)
     (:latex-image-default-option nil nil org-latex-image-default-option)
     (:latex-image-default-width nil nil org-latex-image-default-width)
@@ -708,6 +709,17 @@ This value will not be used if a height is provided."
   :package-version '(Org . "8.0")
   :type 'string)
 
+(defcustom org-latex-image-default-scale ""
+  "Default scale for images.
+This value will not be used if a width or a scale is provided,
+or if the image is wrapped within a \"wrapfigure\",environment.
+Since scale overrides width and height, setting its default
+value should be done only in exceptional circumstances."
+  :group 'org-export-latex
+  :version "25.1"
+  :package-version '(Org . "9.2")
+  :type 'string)
+
 (defcustom org-latex-image-default-height ""
   "Default height for images.
 This value will not be used if a width is provided, or if the
@@ -2374,13 +2386,18 @@ used as a communication channel."
 	  (if (plist-member attr :center) (plist-get attr :center)
 	    (plist-get info :latex-images-centered)))
 	 (comment-include (if (plist-get attr :comment-include) "%" ""))
-	 ;; It is possible to specify width and height in the
-	 ;; ATTR_LATEX line, and also via default variables.
-	 (width (cond ((plist-get attr :width))
+	 ;; It is possible to specify scale or width and height in
+	 ;; the ATTR_LATEX line, and also via default variables.
+	 (scale (cond ((eq float 'wrap) "")
+		      ((plist-get attr :scale))
+		      (t (plist-get info :latex-image-default-scale))))
+	 (width (cond ((org-string-nw-p scale) "")
+		      ((plist-get attr :width))
 		      ((plist-get attr :height) "")
 		      ((eq float 'wrap) "0.48\\textwidth")
 		      (t (plist-get info :latex-image-default-width))))
-	 (height (cond ((plist-get attr :height))
+	 (height (cond ((org-string-nw-p scale) "")
+		       ((plist-get attr :height))
 		       ((or (plist-get attr :width)
 			    (memq float '(figure wrap))) "")
 		       (t (plist-get info :latex-image-default-height))))
@@ -2402,18 +2419,24 @@ used as a communication channel."
 		  (format "\\begin{tikzpicture}[%s]\n%s\n\\end{tikzpicture}"
 			  options
 			  image-code)))
-	  (when (or (org-string-nw-p width) (org-string-nw-p height))
-	    (setq image-code (format "\\resizebox{%s}{%s}{%s}"
-				     (if (org-string-nw-p width) width "!")
-				     (if (org-string-nw-p height) height "!")
-				     image-code))))
+	  (if (org-string-nw-p scale)
+	      (setq image-code
+		    (format "\\scalebox{%s}{%s}" scale image-code))
+	    (when (or (org-string-nw-p width) (org-string-nw-p height))
+	      (setq image-code (format "\\resizebox{%s}{%s}{%s}"
+				       (if (org-string-nw-p width) width "!")
+				       (if (org-string-nw-p height) height "!")
+				       image-code)))))
       ;; For other images:
       ;; - add width and height to options.
       ;; - include the image with \includegraphics.
-      (when (org-string-nw-p width)
-	(setq options (concat options ",width=" width)))
-      (when (org-string-nw-p height)
-	(setq options (concat options ",height=" height)))
+      (if (org-string-nw-p scale)
+	  (setq options (concat options ",scale=" scale))
+	(progn
+	  (when (org-string-nw-p width)
+	    (setq options (concat options ",width=" width)))
+	  (when (org-string-nw-p height)
+	    (setq options (concat options ",height=" height)))))
       (let ((search-option (org-element-property :search-option link)))
         (when (and search-option
                    (equal filetype "pdf")
-- 
2.20.1