Qt图片调整之饱和度调节

原理较简单不作详述

QImage AdjustSaturation(QImage Img, int iSaturateValue)
{
int red, green, blue, nRed, nGreen, nBlue;
int pixels = Img.width() * Img.height();
unsigned int *data = (unsigned int *)Img.bits();

float Increment = iSaturateValue/100.0;

float delta = 0;
float minVal, maxVal;
float L, S;
float alpha;

for (int i = 0; i < pixels; ++i)
{
nRed = qRed(data[i]);
nGreen = qGreen(data[i]);
nBlue = qBlue(data[i]);

minVal = std::min(std::min(nRed, nGreen), nBlue);
maxVal = std::max(std::max(nRed, nGreen), nBlue);
delta = (maxVal - minVal) / 255.0;
L = 0.5*(maxVal + minVal) / 255.0;
S = std::max(0.5*delta / L, 0.5*delta / (1 - L));

if (Increment > 0)
{
alpha = std::max(S, 1 - Increment);
alpha = 1.0 / alpha - 1;
red = nRed + (nRed - L*255.0)*alpha;
red = (red < 0x00) ? 0x00 : (red > 0xff) ? 0xff : red;
green = nGreen + (nGreen - L*255.0)*alpha;
green = (green < 0x00) ? 0x00 : (green > 0xff) ? 0xff : green;
blue = nBlue + (nBlue - L*255.0)*alpha;
blue = (blue < 0x00) ? 0x00 : (blue > 0xff) ? 0xff : blue;
}
else
{
alpha = Increment;
red = L*255.0 + (nRed - L * 255.0)*(1+alpha);
red = (red < 0x00) ? 0x00 : (red > 0xff) ? 0xff : red;
green = L*255.0 + (nGreen - L * 255.0)*(1+alpha);
green = (green < 0x00) ? 0x00 : (green > 0xff) ? 0xff : green;
blue = L*255.0 + (nBlue - L * 255.0)*(1+alpha);
blue = (blue < 0x00) ? 0x00 : (blue > 0xff) ? 0xff : blue;
}

data[i] = qRgba(red, green, blue, qAlpha(data[i]));
}

return Img;
}