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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2015 Andy Wingo <wingo@igalia.com>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix 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 Guix 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 Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (gnu build svg)
#:use-module (srfi srfi-11)
#:export (svg->png))
;; We need Guile-RSVG and Guile-Cairo. Load them lazily, at run time, to
;; allow compilation to proceed. See also <http://bugs.gnu.org/12202>.
(module-autoload! (current-module)
'(rsvg) '(rsvg-handle-new-from-file))
(module-autoload! (current-module)
'(cairo) '(cairo-image-surface-create))
(define* (downscaled-surface surface
#:key
source-width source-height
width height)
"Return a new rendering context where SURFACE is scaled to WIDTH x HEIGHT."
(let ((cr (cairo-create (cairo-image-surface-create 'argb32
width height))))
(cairo-scale cr (/ width source-width) (/ height source-height))
(cairo-set-source-surface cr surface 0 0)
(cairo-pattern-set-filter (cairo-get-source cr) 'best)
(cairo-rectangle cr 0 0 source-width source-height)
(cairo-fill cr)
cr))
(define* (svg->png in-svg out-png
#:key width height)
"Render the file at IN-SVG as a PNG file in OUT-PNG. When WIDTH and HEIGHT
are provided, use them as the dimensions of OUT-PNG; otherwise preserve the
dimensions of IN-SVG."
(define svg
(rsvg-handle-new-from-file in-svg))
(let-values (((origin-width origin-height em ex)
(rsvg-handle-get-dimensions svg)))
(let* ((surf (cairo-image-surface-create 'argb32
origin-width origin-height))
(cr (cairo-create surf)))
(rsvg-handle-render-cairo svg cr)
(cairo-surface-flush surf)
(let ((cr (if (and width height
(not (= width origin-width))
(not (= height origin-height)))
(downscaled-surface surf
#:source-width origin-width
#:source-height origin-height
#:width width
#:height height)
cr)))
(cairo-surface-write-to-png (cairo-get-target cr) out-png)))))
;;; svg.scm ends here
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