cvtColor函数是OpenCV里用于图像颜色空间转换，可以实现RGB颜色、HSV颜色、HSI颜色、lab颜色、YUV颜色等转换，也可以彩色和灰度图互转。
cvtColor原型：
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/** @brief Converts an image from one color space to another. The function converts an input image from one color space to another. In case of a transformation to-from RGB color space, the order of the channels should be specified explicitly (RGB or BGR). Note that the default color format in OpenCV is often referred to as RGB but it is actually BGR (the bytes are reversed). So the first byte in a standard (24-bit) color image will be an 8-bit Blue component, the second byte will be Green, and the third byte will be Red. The fourth, fifth, and sixth bytes would then be the second pixel (Blue, then Green, then Red), and so on. The conventional ranges for R, G, and B channel values are: - 0 to 255 for CV_8U images - 0 to 65535 for CV_16U images - 0 to 1 for CV_32F images In case of linear transformations, the range does not matter. But in case of a non-linear transformation, an input RGB image should be normalized to the proper value range to get the correct results, for example, for RGB \f$\rightarrow\f$ L\*u\*v\* transformation. For example, if you have a 32-bit floating-point image directly converted from an 8-bit image without any scaling, then it will have the 0..255 value range instead of 0..1 assumed by the function. So, before calling #cvtColor , you need first to scale the image down: @code img *= 1./255; cvtColor(img, img, COLOR_BGR2Luv); @endcode If you use #cvtColor with 8-bit images, the conversion will have some information lost. For many applications, this will not be noticeable but it is recommended to use 32-bit images in applications that need the full range of colors or that convert an image before an operation and then convert back. If conversion adds the alpha channel, its value will set to the maximum of corresponding channel range: 255 for CV_8U, 65535 for CV_16U, 1 for CV_32F. @param src input image: 8-bit unsigned, 16-bit unsigned ( CV_16UC... ), or single-precision floating-point. @param dst output image of the same size and depth as src. @param code color space conversion code (see #ColorConversionCodes). @param dstCn number of channels in the destination image; if the parameter is 0, the number of the channels is derived automatically from src and code. @see @ref imgproc_color_conversions */ CV_EXPORTS_W void cvtColor( InputArray src, OutputArray dst, int code, int dstCn = 0 ); |
具体cvtColor函数可以有多少种转换方式，下面列出转换的枚举。
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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 }; |
以上的枚举类型也很好理解，比如COLOR_RGBA2BGR，就是RGBA类型转BGR类型图像。
cvtColor()函数运用实例：
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Mat image = imread("Lena.bmp"); cvtColor(image, image, COLOR_RGB2GRAY); imshow("Image", image); waitKey(0); |