;;; svg.el --- SVG image creation functions -*- lexical-binding: t -*-
;; Copyright (C) 2014-2022 Free Software Foundation, Inc.
;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; Felix E. Klee <felix.klee@inka.de>
;; Keywords: image
;; Version: 1.1
;; Package-Requires: ((emacs "25"))
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; This package allows creating SVG images in Emacs. SVG images are
;; vector-based XML files, really, so you could create them directly
;; as XML. However, that's really tedious, as there are some fiddly
;; bits.
;; In addition, the `svg-insert-image' function allows inserting an
;; SVG image into a buffer that's updated "on the fly" as you
;; add/alter elements to the image, which is useful when composing the
;; images.
;; Here are some usage examples:
;; Create the base image structure, add a gradient spec, and insert it
;; into the buffer:
;;
;; (setq svg (svg-create 800 800 :stroke "orange" :stroke-width 5))
;; (svg-gradient svg "gradient" 'linear '((0 . "red") (100 . "blue")))
;; (save-excursion (goto-char (point-max)) (svg-insert-image svg))
;; Then add various elements to the structure:
;;
;; (svg-rectangle svg 100 100 500 500 :gradient "gradient" :id "rec1")
;; (svg-circle svg 500 500 100 :id "circle1")
;; (svg-ellipse svg 100 100 50 90 :stroke "red" :id "ellipse1")
;; (svg-line svg 100 190 50 100 :id "line1" :stroke "yellow")
;; (svg-polyline svg '((200 . 100) (500 . 450) (80 . 100))
;; :stroke "green" :id "poly1")
;; (svg-polygon svg '((100 . 100) (200 . 150) (150 . 90))
;; :stroke "blue" :fill "red" :id "gon1")
;;; Code:
(require 'cl-lib)
(require 'xml)
(require 'dom)
(defun svg-create (width height &rest args)
"Create a new, empty SVG image with dimensions WIDTH x HEIGHT.
ARGS can be used to provide `stroke' and `stroke-width' parameters to
any further elements added."
(dom-node 'svg
`((width . ,width)
(height . ,height)
(version . "1.1")
(xmlns . "http://www.w3.org/2000/svg")
,@(unless (plist-get args :xmlns:xlink)
'((xmlns:xlink . "http://www.w3.org/1999/xlink")))
,@(svg--arguments nil args))))
(defun svg-gradient (svg id type stops)
"Add a gradient with ID to SVG.
TYPE is `linear' or `radial'.
STOPS is a list of percentage/color pairs."
(svg--def
svg
(apply
#'dom-node
(if (eq type 'linear)
'linearGradient
'radialGradient)
`((id . ,id)
(x1 . 0)
(x2 . 0)
(y1 . 0)
(y2 . 1))
(mapcar
(lambda (stop)
(dom-node 'stop `((offset . ,(format "%s%%" (car stop)))
(stop-color . ,(cdr stop)))))
stops))))
(defun svg-rectangle (svg x y width height &rest args)
"Create a rectangle on SVG, starting at position X/Y, of WIDTH/HEIGHT.
ARGS is a plist of modifiers. Possible values are
:stroke-width PIXELS The line width.
:stroke-color COLOR The line color.
:gradient ID The gradient ID to use."
(svg--append
svg
(dom-node 'rect
`((width . ,width)
(height . ,height)
(x . ,x)
(y . ,y)
,@(svg--arguments svg args)))))
(defun svg-circle (svg x y radius &rest args)
"Create a circle of RADIUS on SVG.
X/Y denote the center of the circle."
(svg--append
svg
(dom-node 'circle
`((cx . ,x)
(cy . ,y)
(r . ,radius)
,@(svg--arguments svg args)))))
(defun svg-ellipse (svg x y x-radius y-radius &rest args)
"Create an ellipse of X-RADIUS/Y-RADIUS on SVG.
X/Y denote the center of the ellipse."
(svg--append
svg
(dom-node 'ellipse
`((cx . ,x)
(cy . ,y)
(rx . ,x-radius)
(ry . ,y-radius)
,@(svg--arguments svg args)))))
(defun svg-line (svg x1 y1 x2 y2 &rest args)
"Create a line starting in X1/Y1, ending at X2/Y2 on SVG."
(svg--append
svg
(dom-node 'line
`((x1 . ,x1)
(x2 . ,x2)
(y1 . ,y1)
(y2 . ,y2)
,@(svg--arguments svg args)))))
(defun svg-polyline (svg points &rest args)
"Create a polyline going through POINTS on SVG.
POINTS is a list of x/y pairs."
(svg--append
svg
(dom-node
'polyline
`((points . ,(mapconcat (lambda (pair)
(format "%s %s" (car pair) (cdr pair)))
points
", "))
,@(svg--arguments svg args)))))
(defun svg-polygon (svg points &rest args)
"Create a polygon going through POINTS on SVG.
POINTS is a list of x/y pairs."
(svg--append
svg
(dom-node
'polygon
`((points . ,(mapconcat (lambda (pair)
(format "%s %s" (car pair) (cdr pair)))
points
", "))
,@(svg--arguments svg args)))))
(defun svg-embed (svg image image-type datap &rest args)
"Insert IMAGE into the SVG structure.
IMAGE should be a file name if DATAP is nil, and a binary string
otherwise. IMAGE-TYPE should be a MIME image type, like
\"image/jpeg\" or the like."
(svg--append
svg
(dom-node
'image
`((xlink:href . ,(svg--image-data image image-type datap))
,@(svg--arguments svg args)))))
(defun svg-embed-base-uri-image (svg relative-filename &rest args)
"Insert image placed at RELATIVE-FILENAME into the SVG structure.
RELATIVE-FILENAME will be searched in `file-name-directory' of the
image's `:base-uri' property. If `:base-uri' is not specified for the
image, then embedding won't work. Embedding large images using this
function is much faster than `svg-embed'."
(svg--append
svg
(dom-node
'image
`((xlink:href . ,relative-filename)
,@(svg--arguments svg args)))))
(defun svg-text (svg text &rest args)
"Add TEXT to SVG."
(svg--append
svg
(dom-node
'text
`(,@(svg--arguments svg args))
(svg--encode-text text))))
(defun svg--encode-text (text)
;; Apparently the SVG renderer needs to have all non-ASCII
;; characters encoded, and only certain special characters.
(with-temp-buffer
(insert text)
(dolist (substitution '(("&" . "&")
("<" . "<")
(">" . ">")))
(goto-char (point-min))
(while (search-forward (car substitution) nil t)
(replace-match (cdr substitution) t t nil)))
(goto-char (point-min))
(while (not (eobp))
(let ((char (following-char)))
(if (< char 128)
(forward-char 1)
(delete-char 1)
(insert "&#" (format "%d" char) ";"))))
(buffer-string)))
(defun svg--append (svg node)
(let ((old (and (dom-attr node 'id)
(dom-by-id svg
(concat "\\`" (regexp-quote (dom-attr node 'id))
"\\'")))))
(if old
;; FIXME: This was (dom-set-attributes old (dom-attributes node))
;; and got changed by commit f7ea7aa11f6211b5142bbcfc41c580d75485ca56
;; without any explanation.
(setcdr (car old) (cdr node))
(dom-append-child svg node)))
(svg-possibly-update-image svg))
(defun svg--image-data (image image-type datap)
(with-temp-buffer
(set-buffer-multibyte nil)
(if datap
(insert image)
(insert-file-contents image))
(base64-encode-region (point-min) (point-max) t)
(goto-char (point-min))
(insert "data:" image-type ";base64,")
(buffer-string)))
(defun svg--arguments (svg args)
(let ((stroke-width (or (plist-get args :stroke-width)
(dom-attr svg 'stroke-width)))
(stroke-color (or (plist-get args :stroke-color)
(dom-attr svg 'stroke-color)))
(fill-color (plist-get args :fill-color))
attr)
(when stroke-width
(push (cons 'stroke-width stroke-width) attr))
(when stroke-color
(push (cons 'stroke stroke-color) attr))
(when fill-color
(push (cons 'fill fill-color) attr))
(when (plist-get args :gradient)
(setq attr
(append
;; We need a way to specify the gradient direction here...
`((x1 . 0)
(x2 . 0)
(y1 . 0)
(y2 . 1)
(fill . ,(format "url(#%s)"
(plist-get args :gradient))))
attr)))
(cl-loop for (key value) on args by #'cddr
unless (memq key '(:stroke-color :stroke-width :gradient
:fill-color))
;; Drop the leading colon.
do (push (cons (intern (substring (symbol-name key) 1) obarray)
value)
attr))
attr))
(defun svg--def (svg def)
(dom-append-child
(or (dom-by-tag svg 'defs)
(let ((node (dom-node 'defs)))
(dom-add-child-before svg node)
node))
def)
svg)
(defun svg-image (svg &rest props)
"Return an image object from SVG.
PROPS is passed on to `create-image' as its PROPS list."
(apply
#'create-image
(with-temp-buffer
(svg-print svg)
(buffer-string))
'svg t props))
(defun svg-insert-image (svg)
"Insert SVG as an image at point.
If the SVG is later changed, the image will also be updated."
(let ((image (svg-image svg))
(marker (point-marker)))
(insert-image image)
(dom-set-attribute svg :image marker)))
(defun svg-possibly-update-image (svg)
(let ((marker (dom-attr svg :image)))
(when (and marker
(buffer-live-p (marker-buffer marker)))
(with-current-buffer (marker-buffer marker)
(put-text-property marker (1+ marker) 'display (svg-image svg))))))
(defun svg-print (dom)
"Convert DOM into a string containing the xml representation."
(if (stringp dom)
(insert dom)
(insert (format "<%s" (car dom)))
(dolist (attr (nth 1 dom))
;; Ignore attributes that start with a colon.
(unless (= (aref (format "%s" (car attr)) 0) ?:)
(insert (format " %s=\"%s\"" (car attr) (cdr attr)))))
(insert ">")
(dolist (elem (nthcdr 2 dom))
(insert " ")
(svg-print elem))
(insert (format "</%s>" (car dom)))))
(defun svg-remove (svg id)
"Remove the element identified by ID from SVG."
(let* ((node (car (dom-by-id
svg
(concat "\\`" (regexp-quote id)
"\\'")))))
(when node (dom-remove-node svg node))))
;; Function body copied from `org-plist-delete' in Emacs 26.1.
(defun svg--plist-delete (plist property)
"Delete PROPERTY from PLIST.
This is in contrast to merely setting it to 0."
(let (p)
(while plist
(if (not (eq property (car plist)))
(setq p (plist-put p (car plist) (nth 1 plist))))
(setq plist (cddr plist)))
p))
(defun svg--path-command-symbol (command-symbol command-args)
(let ((char (symbol-name command-symbol))
(relative (if (plist-member command-args :relative)
(plist-get command-args :relative)
(plist-get command-args :default-relative))))
(intern (if relative (downcase char) (upcase char)))))
(defun svg--elliptical-arc-coordinates (rx ry x y &rest args)
(list
rx ry
(or (plist-get args :x-axis-rotation) 0)
(if (plist-get args :large-arc) 1 0)
(if (plist-get args :sweep) 1 0)
x y))
(defun svg--elliptical-arc-command (coordinates-list &rest args)
(cons
(svg--path-command-symbol 'a args)
(mapcan
(lambda (coordinates)
(apply #'svg--elliptical-arc-coordinates
coordinates))
coordinates-list)))
(defun svg--moveto-command (coordinates-list &rest args)
(cons
(svg--path-command-symbol 'm args)
(mapcan
(lambda (coordinates)
(list (car coordinates) (cdr coordinates)))
coordinates-list)))
(defun svg--closepath-command (&rest args)
(list (svg--path-command-symbol 'z args)))
(defun svg--lineto-command (coordinates-list &rest args)
(cons
(svg--path-command-symbol 'l args)
(mapcan
(lambda (coordinates)
(list (car coordinates) (cdr coordinates)))
coordinates-list)))
(defun svg--horizontal-lineto-command (coordinate-list &rest args)
(cons
(svg--path-command-symbol 'h args)
coordinate-list))
(defun svg--vertical-lineto-command (coordinate-list &rest args)
(cons
(svg--path-command-symbol 'v args)
coordinate-list))
(defun svg--curveto-command (coordinates-list &rest args)
(cons
(svg--path-command-symbol 'c args)
(apply #'append coordinates-list)))
(defun svg--smooth-curveto-command (coordinates-list &rest args)
(cons
(svg--path-command-symbol 's args)
(apply #'append coordinates-list)))
(defun svg--quadratic-bezier-curveto-command (coordinates-list
&rest args)
(cons
(svg--path-command-symbol 'q args)
(apply #'append coordinates-list)))
(defun svg--smooth-quadratic-bezier-curveto-command (coordinates-list
&rest args)
(cons
(svg--path-command-symbol 't args)
(apply #'append coordinates-list)))
(defun svg--eval-path-command (command default-relative)
(cl-letf
(((symbol-function 'moveto) #'svg--moveto-command)
((symbol-function 'closepath) #'svg--closepath-command)
((symbol-function 'lineto) #'svg--lineto-command)
((symbol-function 'horizontal-lineto)
#'svg--horizontal-lineto-command)
((symbol-function 'vertical-lineto)
#'svg--vertical-lineto-command)
((symbol-function 'curveto) #'svg--curveto-command)
((symbol-function 'smooth-curveto)
#'svg--smooth-curveto-command)
((symbol-function 'quadratic-bezier-curveto)
#'svg--quadratic-bezier-curveto-command)
((symbol-function 'smooth-quadratic-bezier-curveto)
#'svg--smooth-quadratic-bezier-curveto-command)
((symbol-function 'elliptical-arc)
#'svg--elliptical-arc-command)
(extended-command (append command (list :default-relative
default-relative))))
(mapconcat #'prin1-to-string (apply extended-command) " ")))
(defun svg-path (svg commands &rest args)
"Add the outline of a shape to SVG according to COMMANDS.
Coordinates by default are absolute. ARGS is a plist of
modifiers. If :relative is t, then coordinates are relative to
the last position, or -- initially -- to the origin."
(let* ((default-relative (plist-get args :relative))
(stripped-args (svg--plist-delete args :relative))
(d (mapconcat #'identity
(mapcar
(lambda (command)
(svg--eval-path-command command
default-relative))
commands) " ")))
(svg--append
svg
(dom-node 'path
`((d . ,d)
,@(svg--arguments svg stripped-args))))))
(defun svg-clip-path (svg &rest args)
"Add a clipping path to SVG, where ARGS is a plist of modifiers.
If applied to a shape via the :clip-path property, parts of that
shape which lie outside of the clipping path are not drawn."
(let ((new-dom-node (dom-node 'clipPath
`(,@(svg--arguments svg args)))))
(svg--append svg new-dom-node)
new-dom-node))
(defun svg-node (svg tag &rest args)
"Add the custom node TAG to SVG."
(let ((new-dom-node (dom-node tag
`(,@(svg--arguments svg args)))))
(svg--append svg new-dom-node)
new-dom-node))
(provide 'svg)
;;; svg.el ends here