基于OpenCV的RGB和HSV色彩空间相互转换C++程序

之所以说基于opencv，由于转换程序用到了一些OpenCV函数及数据类型。

OpenCV全称：Open Source Computer Vision Library，开源、免费，很好很强大。



帮助文档：http://docs.opencv.org/index.html

但凡图像处理软件，都会提供色相、饱和度、明度调整功能，比如常见的PS或者美图秀秀。在调整色相、饱和度、明度时，需要将每个像素点的rgb色彩空间转换到hsv色彩空间，然后做相应计算调整，最后在将计算结果转换回rgb颜色空间进行显示。有关概念及转换公式可以参考：http://zh.wikipedia.org/wiki/HSL%E5%92%8CHSV%E8%89%B2%E5%BD%A9%E7%A9%BA%E9%97%B4，
对于每个颜色向量 (r, g, b)，参照转换公式，两个空间的相互转换就十分简单了。

下面为C++转换代码：

struct BGR
{
uchar b;
uchar g;
uchar r;
};

struct HSV
{
int h;
double s;
double v;
};

bool IsEquals(double val1 , double val2)
{
return fabs(val1 - val2) < 0.001;
}

// BGR(BGR: 0~255)转HSV(H: [0~360), S: [0~1], V: [0~1])
void BGR2HSV(BGR &bgr, HSV &hsv)
{
double b, g, r;
double h, s, v;
double min, max;
double delta;

b = bgr.b / 255.0;
g = bgr.g / 255.0;
r = bgr.r / 255.0;

if (r > g)
{
max = MAX(r, b);
min = MIN(g, b);
}
else
{
max = MAX(g, b);
min = MIN(r, b);
}

v = max;
delta = max - min;

if (IsEquals(max, 0))
{
s = 0.0;
}
else
{
s = delta / max;
}

if (max == min)
{
h = 0.0;
}
else
{
if (IsEquals(r, max) && g >= b)
{
h = 60 * (g - b) / delta + 0;
}
else if (IsEquals(r, max) && g < b)
{
h = 60 * (g - b) / delta + 360;
}
else if (IsEquals(g, max))
{
h = 60 * (b - r) / delta + 120;
}
else if (IsEquals(b, max))
{
h = 60 * (r - g) / delta + 240;
}
}

hsv.h = (int)(h + 0.5);
hsv.h = (hsv.h > 359) ? (hsv.h - 360) : hsv.h;
hsv.h = (hsv.h < 0) ? (hsv. h + 360) : hsv.h;
hsv.s = s;
hsv.v = v;
}

// HSV转BGR
void HSV2BGR(HSV &hsv, BGR &bgr)
{
int h = hsv.h;
double s = hsv. s;
double v = hsv. v;
double b = 0.0;
double g = 0.0;
double r = 0.0;

int flag = (int)abs(h / 60.0);
double f = h/60.0 - flag;
double p = v * (1 - s);
double q = v * (1 - f*s);
double t = v * (1 - (1- f)*s);

switch (flag)
{
case 0:
b = p;
g = t;
r = v;
break;
case 1:
b = p;
g = v;
r = q;
break;
case 2:
b = t;
g = v;
r = p;
break;
case 3:
b = v;
g = q;
r = p;
break;
case 4:
b = v;
g = p;
r = t;
break;
case 5:
b = q;
g = p;
r = v;
break;
default:
break;
}

int blue = int(b * 255);
bgr.b = (blue > 255) ? 255 : blue;
bgr.b = (blue < 0) ? 0 : bgr.b;

int green = int(g * 255);
bgr.g = (green > 255) ? 255 : green;
bgr.g = (green < 0) ? 0 : bgr.g;

int red = int(r * 255);
bgr.r = (red > 255) ? 255 : red;
bgr.r = (red < 0) ? 0 : bgr.r;
}

int main()
{
string imgName = "lena.jpg";
Mat img = cv::imread(imgName);
Mat tmp = img.clone();

if (img.data == NULL)
{
cout<< "Could not open or find the image"<<endl;
return -1;
}

// 色彩空间转换>>自己实现
int row = img.rows;
int col = img.cols * img.channels();
uchar * pImg = NULL;
BGR bgr;
HSV hsv;
for (int i = 0; i < row; i++)
{
pImg = img.ptr<uchar>(i);// 遍历时用img.at()效率会降很多, 很耗时
for (int j = 0; j < col; j+=3)
{
bgr.b = pImg[j];
bgr.g = pImg[j + 1];
bgr.r = pImg[j + 2];
BGR2HSV(bgr, hsv);
hsv.h = hsv.h + 60;//调整色相 +60.取值范围为[0, 360)
hsv.h = (hsv.h > 359) ? (hsv.h - 360) : hsv.h;
hsv.h = (hsv.h < 0)   ? (hsv.h + 360) : hsv.h;
HSV2BGR( hsv, bgr);
pImg[j] = bgr.b;
pImg[j + 1] = bgr.g;
pImg[j + 2] = bgr.r;
}
}
imshow("my", img);

// 色彩空间转换>>调用OpenCV
cvtColor(tmp, tmp, CV_BGR2HSV);
vector<Mat> channels;
split(tmp, channels);
channels[0] += 30;// 调整色相 +30.这里没有做范围判断,opencv的h取值范围为[0, 180)
merge(channels, tmp);
cvtColor(tmp, tmp, CV_HSV2BGR);
imshow("opencv", tmp);
cv::waitKey();

return 0;
}

ps：main()函数中同时提供了调用opencv函数实现的色相调整功能，主要使用了cvtColor()：色彩空间转换、split()：通道分离及merge():通道合并等函数。程序使用的opencv版本为210，运行上述程序还需添加opencv头文件引用以及配置相应lib文件。由于程序只是作为验证demo，所以写的有点乱、不够优化。