renderutils.cpp

/*
    dspdfviewer - Dual Screen PDF Viewer for LaTeX-Beamer
    Copyright (C) 2012  Danny Edel <mail@danny-edel.de>

    This program 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 2 of the License, or
    (at your option) any later version.

    This program 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 this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/


#include "renderutils.h"

#include "debug.h"
#include <QApplication>
#include <stdexcept>

#include <boost/math/special_functions/round.hpp>

using boost::math::iround;

namespace {
	bool shuttingDown = false;
}

QImage RenderUtils::renderPagePart(QSharedPointer< const Poppler::Page > page, QSize targetSize, PagePart whichPart)
{
  if ( ! page )
  {
    throw std::runtime_error( std::string( qPrintable( QApplication::translate("RenderUtils", "RenderUtils::renderPagePart called with null page. Target size was %1x%2").
      arg(targetSize.width()).arg(targetSize.height()) ) ) );
  }

  if ( shuttingDown )
    return QImage();

  /* pagesize in points, (72 points is an inch) */
  QSizeF pagesize = page->pageSizeF();
  QSizeF fullsize = pagesize;

  if ( whichPart != PagePart::FullPage )
  {
    /* Only render half the page */
    pagesize.setWidth(pagesize.width()/2);
  }

  /* Calculate DPI for displaying on size */
  /* the 72 comes from converting from points to inches */
  double dpiWidth = 72.0 * targetSize.width() / pagesize.width();
  double dpiHeight = 72.0 * targetSize.height() / pagesize.height();

  /* Take the smaller one, so that the image surely fits on target area */
  double dpi = std::min(dpiWidth, dpiHeight);

  /* Calculate Page Size in pixels */

  QSize fullSizePixels( iround(dpi * fullsize.width() / 72.0),
			iround(dpi * fullsize.height() / 72.0) );

  /* Calculate rendered image size */
  QSize imageSizePixels( iround(dpi * pagesize.width() / 72.0),
		  iround( dpi * pagesize.height() / 72.0 ) );

  /* Calculate x-offset */
  int x = 0;
  if ( whichPart == PagePart::RightHalf ) {
    /* start at an offset of width() pixels to the right, rounding up */
    x = (fullSizePixels.width()+1)/2;
  }

  /* render it */
  QImage renderedImage =  page->renderToImage(
    dpi, dpi,
    x, /* x-offset */
    0, /* y-offset */
    imageSizePixels.width(),
    imageSizePixels.height()
		      );

  return renderedImage;
}

void RenderUtils::notifyShutdown(void) {
	shuttingDown = true;
}