;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2016, 2017, 2018 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 (rsvg)
  #:use-module (cairo)
  #:use-module (srfi srfi-11)
  #:export (svg->png))

(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-                    GNU GENERAL PUBLIC LICENSE
                       Version 3, 29 June 2007

 Copyright (C) 2007 Free Software Foundation, Inc. &lt;http://fsf.org/&gt;
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

                            Preamble

  The GNU General Public License is a free, copyleft license for
software and other kinds of works.

  The licenses for most software and other practical works are designed
to take away your freedom to share and change the works.  By contrast,
the GNU General Public License is intended to guarantee your freedom to
share and change all versions of a program--to make sure it remains free
software for all its users.  We, the Free Software Foundation, use the
GNU General Public License for most of our software; it applies also to
any other work rel