C++中怎么使用cvtColor实现颜色转换

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前言

在我们读取图像时通常会用到imread（）函数，里面flags可以决定通道数，来得到我们想要的图像，比如：

-1 按解码得到的方式读入图像；

0 单通道 灰度图；

1 三通道 彩色；

当我们想要其他类型的图像时，这种方法就有一些局限性了，所以我们有必要了解cvtColor 这是一种颜色空间转换函数。

源码

void cvtColor(InputArray src, OutputArray dst, int code, int dstCn = 0);src 输入图像dst 输出图像code 代码颜色空间转换代码dstCn 目标图像中的信道数; 如果该参数为0，则通道的数量自动从SRC和code派生。

可以支持RGB HSV 等颜色空间转换（建议不要使用人脸尝试，有些效果懂的都懂）

代码：

int main(){        Mat img1, img2, img3, img4;        img1 = imread("猫1.jpg");        imshow("原图", img1);        cvtColor(img1, img2, COLOR_RGB2GRAY);        imshow("灰度图", img2);        cvtColor(img1, img3, COLOR_RGB2HSV);        imshow("HSV", img3);        cvtColor(img1, img4, COLOR_RGB2BGR);        imshow("BGR", img4);        waitKey(0);}

效果图

代码颜色空间转换代码

enum ColorConversionCodes {    COLOR_BGR2BGRA     = 0, //!< add alpha channel to RGB or BGR image    COLOR_RGB2RGBA     = COLOR_BGR2BGRA,    COLOR_BGRA2BGR     = 1, //!< remove alpha channel from RGB or BGR image    COLOR_RGBA2RGB     = COLOR_BGRA2BGR,    COLOR_BGR2RGBA     = 2, //!< convert between RGB and BGR color spaces (with or without alpha channel)    COLOR_RGB2BGRA     = COLOR_BGR2RGBA,    COLOR_RGBA2BGR     = 3,    COLOR_BGRA2RGB     = COLOR_RGBA2BGR,    COLOR_BGR2RGB      = 4,    COLOR_RGB2BGR      = COLOR_BGR2RGB,    COLOR_BGRA2RGBA    = 5,    COLOR_RGBA2BGRA    = COLOR_BGRA2RGBA,    COLOR_BGR2GRAY     = 6, //!< convert between RGB/BGR and grayscale, @ref color_convert_rgb_gray "color conversions"    COLOR_RGB2GRAY     = 7,    COLOR_GRAY2BGR     = 8,    COLOR_GRAY2RGB     = COLOR_GRAY2BGR,    COLOR_GRAY2BGRA    = 9,    COLOR_GRAY2RGBA    = COLOR_GRAY2BGRA,    COLOR_BGRA2GRAY    = 10,    COLOR_RGBA2GRAY    = 11,    COLOR_BGR2BGR565   = 12, //!< convert between RGB/BGR and BGR565 (16-bit images)    COLOR_RGB2BGR565   = 13,    COLOR_BGR5652BGR   = 14,    COLOR_BGR5652RGB   = 15,    COLOR_BGRA2BGR565  = 16,    COLOR_RGBA2BGR565  = 17,    COLOR_BGR5652BGRA  = 18,    COLOR_BGR5652RGBA  = 19,    COLOR_GRAY2BGR565  = 20, //!< convert between grayscale to BGR565 (16-bit images)    COLOR_BGR5652GRAY  = 21,    COLOR_BGR2BGR555   = 22,  //!< convert between RGB/BGR and BGR555 (16-bit images)    COLOR_RGB2BGR555   = 23,    COLOR_BGR5552BGR   = 24,    COLOR_BGR5552RGB   = 25,    COLOR_BGRA2BGR555  = 26,    COLOR_RGBA2BGR555  = 27,    COLOR_BGR5552BGRA  = 28,    COLOR_BGR5552RGBA  = 29,    COLOR_GRAY2BGR555  = 30, //!< convert between grayscale and BGR555 (16-bit images)    COLOR_BGR5552GRAY  = 31,    COLOR_BGR2XYZ      = 32, //!< convert RGB/BGR to CIE XYZ, @ref color_convert_rgb_xyz "color conversions"    COLOR_RGB2XYZ      = 33,    COLOR_XYZ2BGR      = 34,    COLOR_XYZ2RGB      = 35,    COLOR_BGR2YCrCb    = 36, //!< convert RGB/BGR to luma-chroma (aka YCC), @ref color_convert_rgb_ycrcb "color conversions"    COLOR_RGB2YCrCb    = 37,    COLOR_YCrCb2BGR    = 38,    COLOR_YCrCb2RGB    = 39,    COLOR_BGR2HSV      = 40, //!< convert RGB/BGR to HSV (hue saturation value), @ref color_convert_rgb_hsv "color conversions"    COLOR_RGB2HSV      = 41,    COLOR_BGR2Lab      = 44, //!< convert RGB/BGR to CIE Lab, @ref color_convert_rgb_lab "color conversions"    COLOR_RGB2Lab      = 45,    COLOR_BGR2Luv      = 50, //!< convert RGB/BGR to CIE Luv, @ref color_convert_rgb_luv "color conversions"    COLOR_RGB2Luv      = 51,    COLOR_BGR2HLS      = 52, //!< convert RGB/BGR to HLS (hue lightness saturation), @ref color_convert_rgb_hls "color conversions"    COLOR_RGB2HLS      = 53,    COLOR_HSV2BGR      = 54, //!< backward conversions to RGB/BGR    COLOR_HSV2RGB      = 55,    COLOR_Lab2BGR      = 56,    COLOR_Lab2RGB      = 57,    COLOR_Luv2BGR      = 58,    COLOR_Luv2RGB      = 59,    COLOR_HLS2BGR      = 60,    COLOR_HLS2RGB      = 61,    COLOR_BGR2HSV_FULL = 66,    COLOR_RGB2HSV_FULL = 67,    COLOR_BGR2HLS_FULL = 68,    COLOR_RGB2HLS_FULL = 69,    COLOR_HSV2BGR_FULL = 70,    COLOR_HSV2RGB_FULL = 71,    COLOR_HLS2BGR_FULL = 72,    COLOR_HLS2RGB_FULL = 73,    COLOR_LBGR2Lab     = 74,    COLOR_LRGB2Lab     = 75,    COLOR_LBGR2Luv     = 76,    COLOR_LRGB2Luv     = 77,    COLOR_Lab2LBGR     = 78,    COLOR_Lab2LRGB     = 79,    COLOR_Luv2LBGR     = 80,    COLOR_Luv2LRGB     = 81,    COLOR_BGR2YUV      = 82, //!< convert between RGB/BGR and YUV    COLOR_RGB2YUV      = 83,    COLOR_YUV2BGR      = 84,    COLOR_YUV2RGB      = 85,    //! YUV 4:2:0 family to RGB    COLOR_YUV2RGB_NV12  = 90,    COLOR_YUV2BGR_NV12  = 91,    COLOR_YUV2RGB_NV21  = 92,    COLOR_YUV2BGR_NV21  = 93,    COLOR_YUV420sp2RGB  = COLOR_YUV2RGB_NV21,    COLOR_YUV420sp2BGR  = COLOR_YUV2BGR_NV21,    COLOR_YUV2RGBA_NV12 = 94,    COLOR_YUV2BGRA_NV12 = 95,    COLOR_YUV2RGBA_NV21 = 96,    COLOR_YUV2BGRA_NV21 = 97,    COLOR_YUV420sp2RGBA = COLOR_YUV2RGBA_NV21,    COLOR_YUV420sp2BGRA = COLOR_YUV2BGRA_NV21,    COLOR_YUV2RGB_YV12  = 98,    COLOR_YUV2BGR_YV12  = 99,    COLOR_YUV2RGB_IYUV  = 100,    COLOR_YUV2BGR_IYUV  = 101,    COLOR_YUV2RGB_I420  = COLOR_YUV2RGB_IYUV,    COLOR_YUV2BGR_I420  = COLOR_YUV2BGR_IYUV,    COLOR_YUV420p2RGB   = COLOR_YUV2RGB_YV12,    COLOR_YUV420p2BGR   = COLOR_YUV2BGR_YV12,    COLOR_YUV2RGBA_YV12 = 102,    COLOR_YUV2BGRA_YV12 = 103,    COLOR_YUV2RGBA_IYUV = 104,    COLOR_YUV2BGRA_IYUV = 105,    COLOR_YUV2RGBA_I420 = COLOR_YUV2RGBA_IYUV,    COLOR_YUV2BGRA_I420 = COLOR_YUV2BGRA_IYUV,    COLOR_YUV420p2RGBA  = COLOR_YUV2RGBA_YV12,    COLOR_YUV420p2BGRA  = COLOR_YUV2BGRA_YV12,    COLOR_YUV2GRAY_420  = 106,    COLOR_YUV2GRAY_NV21 = COLOR_YUV2GRAY_420,    COLOR_YUV2GRAY_NV12 = COLOR_YUV2GRAY_420,    COLOR_YUV2GRAY_YV12 = COLOR_YUV2GRAY_420,    COLOR_YUV2GRAY_IYUV = COLOR_YUV2GRAY_420,    COLOR_YUV2GRAY_I420 = COLOR_YUV2GRAY_420,    COLOR_YUV420sp2GRAY = COLOR_YUV2GRAY_420,    COLOR_YUV420p2GRAY  = COLOR_YUV2GRAY_420,    //! YUV 4:2:2 family to RGB    COLOR_YUV2RGB_UYVY = 107,    COLOR_YUV2BGR_UYVY = 108,    //COLOR_YUV2RGB_VYUY = 109,    //COLOR_YUV2BGR_VYUY = 110,    COLOR_YUV2RGB_Y422 = COLOR_YUV2RGB_UYVY,    COLOR_YUV2BGR_Y422 = COLOR_YUV2BGR_UYVY,    COLOR_YUV2RGB_UYNV = COLOR_YUV2RGB_UYVY,    COLOR_YUV2BGR_UYNV = COLOR_YUV2BGR_UYVY,    COLOR_YUV2RGBA_UYVY = 111,    COLOR_YUV2BGRA_UYVY = 112,    //COLOR_YUV2RGBA_VYUY = 113,    //COLOR_YUV2BGRA_VYUY = 114,    COLOR_YUV2RGBA_Y422 = COLOR_YUV2RGBA_UYVY,    COLOR_YUV2BGRA_Y422 = COLOR_YUV2BGRA_UYVY,    COLOR_YUV2RGBA_UYNV = COLOR_YUV2RGBA_UYVY,    COLOR_YUV2BGRA_UYNV = COLOR_YUV2BGRA_UYVY,    COLOR_YUV2RGB_YUY2 = 115,    COLOR_YUV2BGR_YUY2 = 116,    COLOR_YUV2RGB_YVYU = 117,    COLOR_YUV2BGR_YVYU = 118,    COLOR_YUV2RGB_YUYV = COLOR_YUV2RGB_YUY2,    COLOR_YUV2BGR_YUYV = COLOR_YUV2BGR_YUY2,    COLOR_YUV2RGB_YUNV = COLOR_YUV2RGB_YUY2,    COLOR_YUV2BGR_YUNV = COLOR_YUV2BGR_YUY2,    COLOR_YUV2RGBA_YUY2 = 119,    COLOR_YUV2BGRA_YUY2 = 120,    COLOR_YUV2RGBA_YVYU = 121,    COLOR_YUV2BGRA_YVYU = 122,    COLOR_YUV2RGBA_YUYV = COLOR_YUV2RGBA_YUY2,    COLOR_YUV2BGRA_YUYV = COLOR_YUV2BGRA_YUY2,    COLOR_YUV2RGBA_YUNV = COLOR_YUV2RGBA_YUY2,    COLOR_YUV2BGRA_YUNV = COLOR_YUV2BGRA_YUY2,    COLOR_YUV2GRAY_UYVY = 123,    COLOR_YUV2GRAY_YUY2 = 124,    //CV_YUV2GRAY_VYUY    = CV_YUV2GRAY_UYVY,    COLOR_YUV2GRAY_Y422 = COLOR_YUV2GRAY_UYVY,    COLOR_YUV2GRAY_UYNV = COLOR_YUV2GRAY_UYVY,    COLOR_YUV2GRAY_YVYU = COLOR_YUV2GRAY_YUY2,    COLOR_YUV2GRAY_YUYV = COLOR_YUV2GRAY_YUY2,    COLOR_YUV2GRAY_YUNV = COLOR_YUV2GRAY_YUY2,    //! alpha premultiplication    COLOR_RGBA2mRGBA    = 125,    COLOR_mRGBA2RGBA    = 126,    //! RGB to YUV 4:2:0 family    COLOR_RGB2YUV_I420  = 127,    COLOR_BGR2YUV_I420  = 128,    COLOR_RGB2YUV_IYUV  = COLOR_RGB2YUV_I420,    COLOR_BGR2YUV_IYUV  = COLOR_BGR2YUV_I420,    COLOR_RGBA2YUV_I420 = 129,    COLOR_BGRA2YUV_I420 = 130,    COLOR_RGBA2YUV_IYUV = COLOR_RGBA2YUV_I420,    COLOR_BGRA2YUV_IYUV = COLOR_BGRA2YUV_I420,    COLOR_RGB2YUV_YV12  = 131,    COLOR_BGR2YUV_YV12  = 132,    COLOR_RGBA2YUV_YV12 = 133,    COLOR_BGRA2YUV_YV12 = 134,    //! Demosaicing    COLOR_BayerBG2BGR = 46,    COLOR_BayerGB2BGR = 47,    COLOR_BayerRG2BGR = 48,    COLOR_BayerGR2BGR = 49,    COLOR_BayerBG2RGB = COLOR_BayerRG2BGR,    COLOR_BayerGB2RGB = COLOR_BayerGR2BGR,    COLOR_BayerRG2RGB = COLOR_BayerBG2BGR,    COLOR_BayerGR2RGB = COLOR_BayerGB2BGR,    COLOR_BayerBG2GRAY = 86,    COLOR_BayerGB2GRAY = 87,    COLOR_BayerRG2GRAY = 88,    COLOR_BayerGR2GRAY = 89,    //! Demosaicing using Variable Number of Gradients    COLOR_BayerBG2BGR_VNG = 62,    COLOR_BayerGB2BGR_VNG = 63,    COLOR_BayerRG2BGR_VNG = 64,    COLOR_BayerGR2BGR_VNG = 65,    COLOR_BayerBG2RGB_VNG = COLOR_BayerRG2BGR_VNG,    COLOR_BayerGB2RGB_VNG = COLOR_BayerGR2BGR_VNG,    COLOR_BayerRG2RGB_VNG = COLOR_BayerBG2BGR_VNG,    COLOR_BayerGR2RGB_VNG = COLOR_BayerGB2BGR_VNG,    //! Edge-Aware Demosaicing    COLOR_BayerBG2BGR_EA  = 135,    COLOR_BayerGB2BGR_EA  = 136,    COLOR_BayerRG2BGR_EA  = 137,    COLOR_BayerGR2BGR_EA  = 138,    COLOR_BayerBG2RGB_EA  = COLOR_BayerRG2BGR_EA,    COLOR_BayerGB2RGB_EA  = COLOR_BayerGR2BGR_EA,    COLOR_BayerRG2RGB_EA  = COLOR_BayerBG2BGR_EA,    COLOR_BayerGR2RGB_EA  = COLOR_BayerGB2BGR_EA,    //! Demosaicing with alpha channel    COLOR_BayerBG2BGRA = 139,    COLOR_BayerGB2BGRA = 140,    COLOR_BayerRG2BGRA = 141,    COLOR_BayerGR2BGRA = 142,    COLOR_BayerBG2RGBA = COLOR_BayerRG2BGRA,    COLOR_BayerGB2RGBA = COLOR_BayerGR2BGRA,    COLOR_BayerRG2RGBA = COLOR_BayerBG2BGRA,    COLOR_BayerGR2RGBA = COLOR_BayerGB2BGRA,    COLOR_COLORCVT_MAX  = 143};

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