plasma-framework/plasma/private/effects/blur.cpp

#ifndef BLUR_CPP
#define BLUR_CPP

/*
 *   Copyright 2007 Jani Huhtanen <jani.huhtanen@tut.fi>
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License version 2 as
 *   published by the Free Software Foundation
 *
 *   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 Library 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 <cmath>

// Exponential blur, Jani Huhtanen, 2006
//
template<int aprec, int zprec>
static inline void blurinner(unsigned char *bptr, int &zR, int &zG, int &zB, int &zA, int alpha);

template<int aprec,int zprec>
static inline void blurrow(QImage &im, int line, int alpha);

template<int aprec, int zprec>
static inline void blurcol(QImage &im, int col, int alpha);

/*
*  expblur(QImage &img, int radius)
*
*  In-place blur of image 'img' with kernel
*  of approximate radius 'radius'.
*
*  Blurs with two sided exponential impulse
*  response.
*
*  aprec = precision of alpha parameter
*  in fixed-point format 0.aprec
*
*  zprec = precision of state parameters
*  zR,zG,zB and zA in fp format 8.zprec
*/
template<int aprec,int zprec>
void expblur(QImage &img, int radius)
{
  if (radius < 1) {
    return;
  }

  img = img.convertToFormat(QImage::Format_ARGB32_Premultiplied);

  /* Calculate the alpha such that 90% of
     the kernel is within the radius.
     (Kernel extends to infinity)
  */
  int alpha = (int)((1 << aprec) * (1.0f - std::exp(-2.3f / (radius + 1.f))));

  int height = img.height();
  int width = img.width();
  for (int row=0; row<height; row++) {
    blurrow<aprec,zprec>(img, row, alpha);
  }

  for (int col=0; col<width; col++) {
    blurcol<aprec,zprec>(img, col, alpha);
  }
  return;
}

template<int aprec, int zprec>
static inline void blurinner(unsigned char *bptr, int &zR, int &zG, int &zB, int &zA, int alpha)
{
  int R, G, B, A;
  R = *bptr;
  G = *(bptr + 1);
  B = *(bptr + 2);
  A = *(bptr + 3);

  zR += (alpha * ((R << zprec) - zR)) >> aprec;
  zG += (alpha * ((G << zprec) - zG)) >> aprec;
  zB += (alpha * ((B << zprec) - zB)) >> aprec;
  zA += (alpha * ((A << zprec) - zA)) >> aprec;

  *bptr =     zR >> zprec;
  *(bptr+1) = zG >> zprec;
  *(bptr+2) = zB >> zprec;
  *(bptr+3) = zA >> zprec;
}

template<int aprec,int zprec>
static inline void blurrow(QImage &im, int line, int alpha)
{
  int zR, zG, zB, zA;

  QRgb *ptr = (QRgb *)im.scanLine(line);
  int width = im.width();

  zR = *((unsigned char *)ptr    ) << zprec;
  zG = *((unsigned char *)ptr + 1) << zprec;
  zB = *((unsigned char *)ptr + 2) << zprec;
  zA = *((unsigned char *)ptr + 3) << zprec;

  for (int index=1; index<width; index++) {
      blurinner<aprec,zprec>((unsigned char *)&ptr[index],zR,zG,zB,zA,alpha);
  }
  for (int index=width-2; index>=0; index--) {
      blurinner<aprec,zprec>((unsigned char *)&ptr[index],zR,zG,zB,zA,alpha);
  }
}

template<int aprec, int zprec>
static inline void blurcol(QImage &im, int col, int alpha)
{
  int zR, zG, zB, zA;

  QRgb *ptr = (QRgb *)im.bits();
  ptr += col;
  int height = im.height();
  int width = im.width();

  zR = *((unsigned char *)ptr    ) << zprec;
  zG = *((unsigned char *)ptr + 1) << zprec;
  zB = *((unsigned char *)ptr + 2) << zprec;
  zA = *((unsigned char *)ptr + 3) << zprec;

  for (int index=width; index<(height-1)*width; index+=width) {
      blurinner<aprec,zprec>((unsigned char *)&ptr[index], zR, zG, zB, zA, alpha);
  }

  for (int index=(height-2)*width; index>=0; index-=width) {
      blurinner<aprec,zprec>((unsigned char *)&ptr[index], zR, zG, zB, zA, alpha);
  }
}

template<class T>
inline const T &qClamp(const T &x, const T &low, const T &high)
{
    if (x <  low) {
        return low;
    } else if (x > high) {
        return high;
    } else {
        return x;
    }
}

#endif