plasma-framework/effects/blur.cpp

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#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;
/* Calculate the alpha such that 90% of
the kernel is within the radius.
(Kernel extends to infinity)
*/
int alpha = (int)((1<<aprec)*(1.0f-expf(-2.3f/(radius+1.f))));
for(int row=0;row<img.height();row++)
{
blurrow<aprec,zprec>(img,row,alpha);
}
for(int col=0;col<img.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);
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<im.width(); index++)
{
blurinner<aprec,zprec>((unsigned char *)&ptr[index],zR,zG,zB,zA,alpha);
}
for(int index=im.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;
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=im.width(); index<(im.height()-1)*im.width(); index+=im.width())
{
blurinner<aprec,zprec>((unsigned char *)&ptr[index],zR,zG,zB,zA,alpha);
}
for(int index=(im.height()-2)*im.width(); index>=0; index-=im.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;
}