颜色转换 cvtColor —— opencv学习记录（三）

颜色转换 cvtColor —— opencv学习记录（三） mini菜 2023-07-10 11:00:13 705
OpenCV
图像处理
C++

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。
先看源码： 

  1. void cvtColor(InputArray src, OutputArray dst, int code, int dstCn = 0);
  3. src 输入图像
  4. dst 输出图像
  5. code 代码颜色空间转换代码
  6. 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：

  1. int main()
  2. {
  3.     Mat img1, img2, img3, img4;
  4.     img1 = imread("猫1.jpg");
  5.     imshow("原图", img1);
  6.     cvtColor(img1, img2, COLOR_RGB2GRAY);
  7.     imshow("灰度图", img2);
  8.     cvtColor(img1, img3, COLOR_RGB2HSV);
  9.     imshow("HSV", img3);
  10.     cvtColor(img1, img4, COLOR_RGB2BGR);
  11.     imshow("BGR", img4);
  12.     waitKey(0);
  13. }

效果图：

附：代码颜色空间转换代码

  1. enum ColorConversionCodes {
  2.     COLOR_BGR2BGRA     = 0, //!< add alpha channel to RGB or BGR image
  3.     COLOR_RGB2RGBA     = COLOR_BGR2BGRA,
  5.     COLOR_BGRA2BGR     = 1, //!< remove alpha channel from RGB or BGR image
  6.     COLOR_RGBA2RGB     = COLOR_BGRA2BGR,
  8.     COLOR_BGR2RGBA     = 2, //!< convert between RGB and BGR color spaces (with or without alpha channel)
  9.     COLOR_RGB2BGRA     = COLOR_BGR2RGBA,
  11.     COLOR_RGBA2BGR     = 3,
  12.     COLOR_BGRA2RGB     = COLOR_RGBA2BGR,
  14.     COLOR_BGR2RGB      = 4,
  15.     COLOR_RGB2BGR      = COLOR_BGR2RGB,
  17.     COLOR_BGRA2RGBA    = 5,
  18.     COLOR_RGBA2BGRA    = COLOR_BGRA2RGBA,
  20.     COLOR_BGR2GRAY     = 6, //!< convert between RGB/BGR and grayscale, @ref color_convert_rgb_gray "color conversions"
  21.     COLOR_RGB2GRAY     = 7,
  22.     COLOR_GRAY2BGR     = 8,
  23.     COLOR_GRAY2RGB     = COLOR_GRAY2BGR,
  24.     COLOR_GRAY2BGRA    = 9,
  25.     COLOR_GRAY2RGBA    = COLOR_GRAY2BGRA,
  26.     COLOR_BGRA2GRAY    = 10,
  27.     COLOR_RGBA2GRAY    = 11,
  29.     COLOR_BGR2BGR565   = 12, //!< convert between RGB/BGR and BGR565 (16-bit images)
  30.     COLOR_RGB2BGR565   = 13,
  31.     COLOR_BGR5652BGR   = 14,
  32.     COLOR_BGR5652RGB   = 15,
  33.     COLOR_BGRA2BGR565  = 16,
  34.     COLOR_RGBA2BGR565  = 17,
  35.     COLOR_BGR5652BGRA  = 18,
  36.     COLOR_BGR5652RGBA  = 19,
  38.     COLOR_GRAY2BGR565  = 20, //!< convert between grayscale to BGR565 (16-bit images)
  39.     COLOR_BGR5652GRAY  = 21,
  41.     COLOR_BGR2BGR555   = 22,  //!< convert between RGB/BGR and BGR555 (16-bit images)
  42.     COLOR_RGB2BGR555   = 23,
  43.     COLOR_BGR5552BGR   = 24,
  44.     COLOR_BGR5552RGB   = 25,
  45.     COLOR_BGRA2BGR555  = 26,
  46.     COLOR_RGBA2BGR555  = 27,
  47.     COLOR_BGR5552BGRA  = 28,
  48.     COLOR_BGR5552RGBA  = 29,
  50.     COLOR_GRAY2BGR555  = 30, //!< convert between grayscale and BGR555 (16-bit images)
  51.     COLOR_BGR5552GRAY  = 31,
  53.     COLOR_BGR2XYZ      = 32, //!< convert RGB/BGR to CIE XYZ, @ref color_convert_rgb_xyz "color conversions"
  54.     COLOR_RGB2XYZ      = 33,
  55.     COLOR_XYZ2BGR      = 34,
  56.     COLOR_XYZ2RGB      = 35,
  58.     COLOR_BGR2YCrCb    = 36, //!< convert RGB/BGR to luma-chroma (aka YCC), @ref color_convert_rgb_ycrcb "color conversions"
  59.     COLOR_RGB2YCrCb    = 37,
  60.     COLOR_YCrCb2BGR    = 38,
  61.     COLOR_YCrCb2RGB    = 39,
  63.     COLOR_BGR2HSV      = 40, //!< convert RGB/BGR to HSV (hue saturation value), @ref color_convert_rgb_hsv "color conversions"
  64.     COLOR_RGB2HSV      = 41,
  66.     COLOR_BGR2Lab      = 44, //!< convert RGB/BGR to CIE Lab, @ref color_convert_rgb_lab "color conversions"
  67.     COLOR_RGB2Lab      = 45,
  69.     COLOR_BGR2Luv      = 50, //!< convert RGB/BGR to CIE Luv, @ref color_convert_rgb_luv "color conversions"
  70.     COLOR_RGB2Luv      = 51,
  71.     COLOR_BGR2HLS      = 52, //!< convert RGB/BGR to HLS (hue lightness saturation), @ref color_convert_rgb_hls "color conversions"
  72.     COLOR_RGB2HLS      = 53,
  74.     COLOR_HSV2BGR      = 54, //!< backward conversions to RGB/BGR
  75.     COLOR_HSV2RGB      = 55,
  77.     COLOR_Lab2BGR      = 56,
  78.     COLOR_Lab2RGB      = 57,
  79.     COLOR_Luv2BGR      = 58,
  80.     COLOR_Luv2RGB      = 59,
  81.     COLOR_HLS2BGR      = 60,
  82.     COLOR_HLS2RGB      = 61,
  84.     COLOR_BGR2HSV_FULL = 66,
  85.     COLOR_RGB2HSV_FULL = 67,
  86.     COLOR_BGR2HLS_FULL = 68,
  87.     COLOR_RGB2HLS_FULL = 69,
  89.     COLOR_HSV2BGR_FULL = 70,
  90.     COLOR_HSV2RGB_FULL = 71,
  91.     COLOR_HLS2BGR_FULL = 72,
  92.     COLOR_HLS2RGB_FULL = 73,
  94.     COLOR_LBGR2Lab     = 74,
  95.     COLOR_LRGB2Lab     = 75,
  96.     COLOR_LBGR2Luv     = 76,
  97.     COLOR_LRGB2Luv     = 77,
  99.     COLOR_Lab2LBGR     = 78,
  100.     COLOR_Lab2LRGB     = 79,
  101.     COLOR_Luv2LBGR     = 80,
  102.     COLOR_Luv2LRGB     = 81,
  104.     COLOR_BGR2YUV      = 82, //!< convert between RGB/BGR and YUV
  105.     COLOR_RGB2YUV      = 83,
  106.     COLOR_YUV2BGR      = 84,
  107.     COLOR_YUV2RGB      = 85,
  109.     //! YUV 4:2:0 family to RGB
  110.     COLOR_YUV2RGB_NV12  = 90,
  111.     COLOR_YUV2BGR_NV12  = 91,
  112.     COLOR_YUV2RGB_NV21  = 92,
  113.     COLOR_YUV2BGR_NV21  = 93,
  114.     COLOR_YUV420sp2RGB  = COLOR_YUV2RGB_NV21,
  115.     COLOR_YUV420sp2BGR  = COLOR_YUV2BGR_NV21,
  117.     COLOR_YUV2RGBA_NV12 = 94,
  118.     COLOR_YUV2BGRA_NV12 = 95,
  119.     COLOR_YUV2RGBA_NV21 = 96,
  120.     COLOR_YUV2BGRA_NV21 = 97,
  121.     COLOR_YUV420sp2RGBA = COLOR_YUV2RGBA_NV21,
  122.     COLOR_YUV420sp2BGRA = COLOR_YUV2BGRA_NV21,
  124.     COLOR_YUV2RGB_YV12  = 98,
  125.     COLOR_YUV2BGR_YV12  = 99,
  126.     COLOR_YUV2RGB_IYUV  = 100,
  127.     COLOR_YUV2BGR_IYUV  = 101,
  128.     COLOR_YUV2RGB_I420  = COLOR_YUV2RGB_IYUV,
  129.     COLOR_YUV2BGR_I420  = COLOR_YUV2BGR_IYUV,
  130.     COLOR_YUV420p2RGB   = COLOR_YUV2RGB_YV12,
  131.     COLOR_YUV420p2BGR   = COLOR_YUV2BGR_YV12,
  133.     COLOR_YUV2RGBA_YV12 = 102,
  134.     COLOR_YUV2BGRA_YV12 = 103,
  135.     COLOR_YUV2RGBA_IYUV = 104,
  136.     COLOR_YUV2BGRA_IYUV = 105,
  137.     COLOR_YUV2RGBA_I420 = COLOR_YUV2RGBA_IYUV,
  138.     COLOR_YUV2BGRA_I420 = COLOR_YUV2BGRA_IYUV,
  139.     COLOR_YUV420p2RGBA  = COLOR_YUV2RGBA_YV12,
  140.     COLOR_YUV420p2BGRA  = COLOR_YUV2BGRA_YV12,
  142.     COLOR_YUV2GRAY_420  = 106,
  143.     COLOR_YUV2GRAY_NV21 = COLOR_YUV2GRAY_420,
  144.     COLOR_YUV2GRAY_NV12 = COLOR_YUV2GRAY_420,
  145.     COLOR_YUV2GRAY_YV12 = COLOR_YUV2GRAY_420,
  146.     COLOR_YUV2GRAY_IYUV = COLOR_YUV2GRAY_420,
  147.     COLOR_YUV2GRAY_I420 = COLOR_YUV2GRAY_420,
  148.     COLOR_YUV420sp2GRAY = COLOR_YUV2GRAY_420,
  149.     COLOR_YUV420p2GRAY  = COLOR_YUV2GRAY_420,
  151.     //! YUV 4:2:2 family to RGB
  152.     COLOR_YUV2RGB_UYVY = 107,
  153.     COLOR_YUV2BGR_UYVY = 108,
  154.     //COLOR_YUV2RGB_VYUY = 109,
  155.     //COLOR_YUV2BGR_VYUY = 110,
  156.     COLOR_YUV2RGB_Y422 = COLOR_YUV2RGB_UYVY,
  157.     COLOR_YUV2BGR_Y422 = COLOR_YUV2BGR_UYVY,
  158.     COLOR_YUV2RGB_UYNV = COLOR_YUV2RGB_UYVY,
  159.     COLOR_YUV2BGR_UYNV = COLOR_YUV2BGR_UYVY,
  161.     COLOR_YUV2RGBA_UYVY = 111,
  162.     COLOR_YUV2BGRA_UYVY = 112,
  163.     //COLOR_YUV2RGBA_VYUY = 113,
  164.     //COLOR_YUV2BGRA_VYUY = 114,
  165.     COLOR_YUV2RGBA_Y422 = COLOR_YUV2RGBA_UYVY,
  166.     COLOR_YUV2BGRA_Y422 = COLOR_YUV2BGRA_UYVY,
  167.     COLOR_YUV2RGBA_UYNV = COLOR_YUV2RGBA_UYVY,
  168.     COLOR_YUV2BGRA_UYNV = COLOR_YUV2BGRA_UYVY,
  170.     COLOR_YUV2RGB_YUY2 = 115,
  171.     COLOR_YUV2BGR_YUY2 = 116,
  172.     COLOR_YUV2RGB_YVYU = 117,
  173.     COLOR_YUV2BGR_YVYU = 118,
  174.     COLOR_YUV2RGB_YUYV = COLOR_YUV2RGB_YUY2,
  175.     COLOR_YUV2BGR_YUYV = COLOR_YUV2BGR_YUY2,
  176.     COLOR_YUV2RGB_YUNV = COLOR_YUV2RGB_YUY2,
  177.     COLOR_YUV2BGR_YUNV = COLOR_YUV2BGR_YUY2,
  179.     COLOR_YUV2RGBA_YUY2 = 119,
  180.     COLOR_YUV2BGRA_YUY2 = 120,
  181.     COLOR_YUV2RGBA_YVYU = 121,
  182.     COLOR_YUV2BGRA_YVYU = 122,
  183.     COLOR_YUV2RGBA_YUYV = COLOR_YUV2RGBA_YUY2,
  184.     COLOR_YUV2BGRA_YUYV = COLOR_YUV2BGRA_YUY2,
  185.     COLOR_YUV2RGBA_YUNV = COLOR_YUV2RGBA_YUY2,
  186.     COLOR_YUV2BGRA_YUNV = COLOR_YUV2BGRA_YUY2,
  188.     COLOR_YUV2GRAY_UYVY = 123,
  189.     COLOR_YUV2GRAY_YUY2 = 124,
  190.     //CV_YUV2GRAY_VYUY    = CV_YUV2GRAY_UYVY,
  191.     COLOR_YUV2GRAY_Y422 = COLOR_YUV2GRAY_UYVY,
  192.     COLOR_YUV2GRAY_UYNV = COLOR_YUV2GRAY_UYVY,
  193.     COLOR_YUV2GRAY_YVYU = COLOR_YUV2GRAY_YUY2,
  194.     COLOR_YUV2GRAY_YUYV = COLOR_YUV2GRAY_YUY2,
  195.     COLOR_YUV2GRAY_YUNV = COLOR_YUV2GRAY_YUY2,
  197.     //! alpha premultiplication
  198.     COLOR_RGBA2mRGBA    = 125,
  199.     COLOR_mRGBA2RGBA    = 126,
  201.     //! RGB to YUV 4:2:0 family
  202.     COLOR_RGB2YUV_I420  = 127,
  203.     COLOR_BGR2YUV_I420  = 128,
  204.     COLOR_RGB2YUV_IYUV  = COLOR_RGB2YUV_I420,
  205.     COLOR_BGR2YUV_IYUV  = COLOR_BGR2YUV_I420,
  207.     COLOR_RGBA2YUV_I420 = 129,
  208.     COLOR_BGRA2YUV_I420 = 130,
  209.     COLOR_RGBA2YUV_IYUV = COLOR_RGBA2YUV_I420,
  210.     COLOR_BGRA2YUV_IYUV = COLOR_BGRA2YUV_I420,
  211.     COLOR_RGB2YUV_YV12  = 131,
  212.     COLOR_BGR2YUV_YV12  = 132,
  213.     COLOR_RGBA2YUV_YV12 = 133,
  214.     COLOR_BGRA2YUV_YV12 = 134,
  216.     //! Demosaicing
  217.     COLOR_BayerBG2BGR = 46,
  218.     COLOR_BayerGB2BGR = 47,
  219.     COLOR_BayerRG2BGR = 48,
  220.     COLOR_BayerGR2BGR = 49,
  222.     COLOR_BayerBG2RGB = COLOR_BayerRG2BGR,
  223.     COLOR_BayerGB2RGB = COLOR_BayerGR2BGR,
  224.     COLOR_BayerRG2RGB = COLOR_BayerBG2BGR,
  225.     COLOR_BayerGR2RGB = COLOR_BayerGB2BGR,
  227.     COLOR_BayerBG2GRAY = 86,
  228.     COLOR_BayerGB2GRAY = 87,
  229.     COLOR_BayerRG2GRAY = 88,
  230.     COLOR_BayerGR2GRAY = 89,
  232.     //! Demosaicing using Variable Number of Gradients
  233.     COLOR_BayerBG2BGR_VNG = 62,
  234.     COLOR_BayerGB2BGR_VNG = 63,
  235.     COLOR_BayerRG2BGR_VNG = 64,
  236.     COLOR_BayerGR2BGR_VNG = 65,
  238.     COLOR_BayerBG2RGB_VNG = COLOR_BayerRG2BGR_VNG,
  239.     COLOR_BayerGB2RGB_VNG = COLOR_BayerGR2BGR_VNG,
  240.     COLOR_BayerRG2RGB_VNG = COLOR_BayerBG2BGR_VNG,
  241.     COLOR_BayerGR2RGB_VNG = COLOR_BayerGB2BGR_VNG,
  243.     //! Edge-Aware Demosaicing
  244.     COLOR_BayerBG2BGR_EA  = 135,
  245.     COLOR_BayerGB2BGR_EA  = 136,
  246.     COLOR_BayerRG2BGR_EA  = 137,
  247.     COLOR_BayerGR2BGR_EA  = 138,
  249.     COLOR_BayerBG2RGB_EA  = COLOR_BayerRG2BGR_EA,
  250.     COLOR_BayerGB2RGB_EA  = COLOR_BayerGR2BGR_EA,
  251.     COLOR_BayerRG2RGB_EA  = COLOR_BayerBG2BGR_EA,
  252.     COLOR_BayerGR2RGB_EA  = COLOR_BayerGB2BGR_EA,
  254.     //! Demosaicing with alpha channel
  255.     COLOR_BayerBG2BGRA = 139,
  256.     COLOR_BayerGB2BGRA = 140,
  257.     COLOR_BayerRG2BGRA = 141,
  258.     COLOR_BayerGR2BGRA = 142,
  260.     COLOR_BayerBG2RGBA = COLOR_BayerRG2BGRA,
  261.     COLOR_BayerGB2RGBA = COLOR_BayerGR2BGRA,
  262.     COLOR_BayerRG2RGBA = COLOR_BayerBG2BGRA,
  263.     COLOR_BayerGR2RGBA = COLOR_BayerGB2BGRA,
  265.     COLOR_COLORCVT_MAX  = 143
  266. };
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