'White balance/color temperature algorithm

I have a picture(RGB) and i wanna adjust color temperature, like in Lightroom. I try converting RGB to LAB and adjust B channel, but it's wrong. May be someone can help with sample code or algorithm of color temperature implementation? Like this:

rgb temperature(int temp, rgb color);

where value - temperature, color - input color (from image), return value - output color (adjusted)

Now, I use this algorithm. RGBtoLAB and LABtoRGB I took from: http://www.easyrgb.com/index.php?X=MATH&H=01#text1

for (int i = 0; i < img.pixCount; i++)
{
    lab32f lab = RGBtoLAB(img.getPixel(i));  
    lab.b += temp.value;  // -100..100
    img.setPixel(i, LABtoRGB(lab));
}

Result images:

Result images