void PLFilterThreshold::Apply(PLBmpBase * pBmpSource, PLBmp * pBmpDest) const
{
int threshold_min = m_threshold_min;
int threshold_max = m_threshold_max;
int channel = m_channel;
// Only works for 32 bpp bitmaps at the moment.
PLASSERT (pBmpSource->GetBitsPerPixel() == 32);
pBmpDest->Create (pBmpSource->GetWidth(), pBmpSource->GetHeight(),
PLPixelFormat::L8, NULL, 0, pBmpSource->GetResolution());
PLBYTE ** pSrcLines = pBmpSource->GetLineArray();
PLBYTE ** pDstLines = pBmpDest->GetLineArray();
for (int y = 0; y<pBmpDest->GetHeight(); ++y)
{ // For each line
PLBYTE * pSrcPixel = pSrcLines[y];
PLBYTE * pDstPixel = pDstLines[y];
for (int x = 0; x < pBmpDest->GetWidth(); ++x)
{ // For each pixel
if ((PLBYTE (pSrcPixel[channel]) <= PLBYTE (threshold_min)) ||
(PLBYTE (pSrcPixel[channel]) >= PLBYTE(threshold_max)))
*pDstPixel = 0;
else
*pDstPixel = pSrcPixel[channel];
pSrcPixel += sizeof(PLPixel32);
++pDstPixel;
}
}
}
PLPixel24 hls2rgb (double h, double l, double s)
{
double m1, m2;
l /= 255;
s /= 100;
// Warning: Foley, van Dam has a typo on the next line!
m2 = (l<=0.5)?(l*(1.0+s)):(l+s-l*s);
m1 = 2.0*l-m2;
if (s<0.001)
return PLPixel24(PLBYTE(l*255), PLBYTE(l*255), PLBYTE(l*255));
else
{
return PLPixel24(hls_value(m1,m2,h+120.0),
hls_value(m1,m2,h),
hls_value(m1,m2,h-120.0));
}
}
// From Foley, van Dam p. 596
PLBYTE hls_value(double n1, double n2, double hue)
{
if (hue>360)
hue-=360;
if (hue<0)
hue+=360;
double rv;
if (hue<60)
rv = n1+(n2-n1)*hue/60.0;
else if (hue<180)
rv = n2;
else if (hue<240)
rv = n1+(n2-n1)*(240.0-hue)/60.0;
else
rv = n1;
return PLBYTE(rv*255);
}
