C实现改变彩色图像亮度

对于灰度图像，改变亮度只需同时增加或减少整张图像的灰度值即可，但是对于彩色图像，相对来说就比较麻烦点。对RGB空间的图像来说，需将RGB空间转换到HSL，H是色调，S是饱和度，L是亮度。改变亮度时将RGB颜色转换成HSL表示，修改L，其他不变，再将HSL转换为RGB。
公式：
RGB to HSL：

HSL to RGB：

代码实现：

#ifndef max#define max(a,b)            (((a) > (b)) ? (a) : (b))#endif#ifndef min#define min(a,b)            (((a) < (b)) ? (a) : (b))#endifvoid RGB32ChangeBright1(uint8_t* src, int width, int height, float factor){    int i,j;    uint32_t* img;    float r,g,b;    uint32_t color;    float h, s, l;    float m,M;    float f,d;    float tr,tg,tb;    float p,q;    float ntr,ntg,ntb;    img = (uint32_t*)src;    for (i = 0; i < height; i++)    {        for (j = 0; j < width; j++)        {            //RGB to HSL            color = *img;            r = (float)(color & 0x000000FF);            g = (float)((color >> 8) & 0x000000FF);            b = (float)((color >> 16) & 0x000000FF);            r /= 255.0;            g /= 255.0;            b /= 255.0;            m = min(min(r,g),b),            M = max(max(r,g),b);            l = (m + M)/2;            if (M==m) h = s = 0.0;            else            {                f = (r==m)?(g-b):((g==m)?(b-r):(r-g));                d = (r==m)?3.0f:((g==m)?5.0f:1.0f);                h = (d - f/(M-m));                if (h>=6.0)                     h-=6;                h*=60;                s = (2*l<=1)?((M-m)/(M+m)):((M-m)/(2-M-m));            }            l += factor;            if (l < 0)            {                l = 0;            }            if (l > 1.0)            {                l = 1.0;            }            //HSL to RGB            q = 2*l<1?l*(1+s):(l+s-l*s);            p = 2*l-q;            h = h/360;            tr = h + ONE_THIRD;            tg = h;            tb = h - ONE_THIRD;            ntr = tr<0?tr+1:(tr>1?tr-1:tr);            ntg = tg<0?tg+1:(tg>1?tg-1:tg);            ntb = tb<0?tb+1:(tb>1?tb-1:tb);            r = 255*(6*ntr<1?p+(q-p)*6*ntr:(2*ntr<1?q:(3*ntr<2?p+(q-p)*6*(2.0f*ONE_THIRD-ntr):p))),            g = 255*(6*ntg<1?p+(q-p)*6*ntg:(2*ntg<1?q:(3*ntg<2?p+(q-p)*6*(2.0f*ONE_THIRD-ntg):p))),            b = 255*(6*ntb<1?p+(q-p)*6*ntb:(2*ntb<1?q:(3*ntb<2?p+(q-p)*6*(2.0f*ONE_THIRD-ntb):p)));            color &= 0xFF000000;            color =  (uint8_t)(r<0?0:(r>255?255:r)) + ((uint8_t)(g<0?0:(g>255?255:g)) << 8) +  ((uint8_t)(b<0?0:(b>255?255:b)) << 16);            //            *img = color;            img++;        }    }}

测试效果：
原图：

效果图，测试参数0.2