opencv|opencv学习笔记（三）颜色转换 cvtColor opencv|c++

【opencv|opencv学习笔记（三）颜色转换 cvtColor】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：

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：

文章图片

文章图片

附：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 };