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List:       kde-devel
Subject:    Re: [OT] Any plans to keep up with longhorn?
From:       Joachim Eibl <joachim.eibl () gmx ! de>
Date:       2003-11-06 22:58:44
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> > Well, browsers could include some "intelligent bitmap stretching" algo,
> > which takes resolution into account. It would not be too difficult.
>
> Essentially all it needs is a fast processor and some hefty memory. You
> upsample the image, apply a 2D FIR or IIR filter so that aliasing is
> removed, and you downsample it afterwards. Or a similar algorithm. The
> trick is that your filter should offer a sharp, almost brickboard cutoff.
> If you do it that way, the bitmap scaling is seamless, i.e. your bitmap
> could be scaled by a factor pi:1 and look as good as scaled by a factor
> 2:1.

Before doing that, you might want to try to optimize the little code snippet 
below.

Does any KDE-Image viewer support something like this? If not, I hope they 
will!

Cheers,
Joachim


/* Copyright (C) Joachim Eibl 2003
    Licence: GPL version 2 */
QImage smoothResize( int xSize, int ySize, QImage& inputImg )
{
   if( inputImg.isNull() )
      return;

   QImage outputImg;
   outputImg.create(xSize, ySize, 32);

   int inWidth = inputImg.width();
   int inHeight = inputImg.height();

   xFactor = (double)xSize/inWidth;
   yFactor = (double)ySize/inHeight;
   for ( x=0; x<xSize; ++x )
   {
      for ( y=0; y<ySize; ++y )
      {
         double xOrig = x / xFactor;
         double yOrig = y / yFactor;
         double dx = xOrig - floor( xOrig );
         double dy = yOrig - floor( yOrig );
         double f1 = (1-dx)*(1-dy);   // Interpolation
         double f2 = dx * (1-dy);
         double f3 = (1-dx)*dy;
         double f4 = dx*dy;
         int xo = min(int(floor(xOrig)),inWidth-1);
         int yo = min(int(floor(yOrig)),inHeight-1);
         int xo1 = min(int(floor(xOrig))+1,inWidth-1);
         int yo1 = min(int(floor(yOrig))+1,inHeight-1);
         QRgb c1 = inputImg.pixel( xo, yo );
         QRgb c2 = inputImg.pixel( xo1, yo );
         QRgb c3 = inputImg.pixel( xo, yo1 );
         QRgb c4 = inputImg.pixel( xo1, yo1 );

         int r=int( f1*qRed(c1)+f2*qRed(c2)+f3*qRed(c3)+f4*qRed(c4) );
         int g=int( f1*qGreen(c1)+f2*qGreen(c2)+f3*qGreen(c3)+f4*qGreen(c4));
         int b=int( f1*qBlue(c1)+f2*qBlue(c2)+f3*qBlue(c3)+f4*qBlue(c4) );
         outputImg.setPixel( x,y, qRgb(r,g,b) );
      }
   }
   return outputImg;
}


 
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