Opencv has its own color operation

The sample code is as follows ：

void demo::color_style(Mat& image)
{
    int colormap[] = {
        COLORMAP_AUTUMN,
        COLORMAP_BONE,
        COLORMAP_CIVIDIS,
        COLORMAP_COOL,
        COLORMAP_HOT,
        COLORMAP_HSV,
        COLORMAP_INFERNO,
        COLORMAP_JET,
        COLORMAP_MAGMA,
        COLORMAP_OCEAN,
        COLORMAP_PARULA,
        COLORMAP_PINK,
        COLORMAP_PLASMA,
        COLORMAP_RAINBOW,
        COLORMAP_SPRING,
        COLORMAP_SUMMER,
        COLORMAP_TWILIGHT,
        COLORMAP_TWILIGHT_SHIFTED,
        COLORMAP_VIRIDIS,
        COLORMAP_WINTER

    };
    Mat dsc;
    int index = 0;
    while (true)
    {
        int c = waitKey(500);
        if (c == 27)
            break;
        applyColorMap(image, dsc, colormap[index % 20]);
        index++;
        imshow(" Image type ", dsc);

    }
}

Here's the point applyColorMap() function , It states in imgproc.hpp

CV_EXPORTS_W void applyColorMap(InputArray src, OutputArray dst, int colormap);

In front of the definition of this function above , We can also see the following ：

enum ColormapTypes
{
    COLORMAP_AUTUMN = 0, //!< 
    COLORMAP_BONE = 1, //!< 
    COLORMAP_JET = 2, //!< 
    COLORMAP_WINTER = 3, //!< 
    COLORMAP_RAINBOW = 4, //!< 
    COLORMAP_OCEAN = 5, //!< 
    COLORMAP_SUMMER = 6, //!< 
    COLORMAP_SPRING = 7, //!< 
    COLORMAP_COOL = 8, //!< 
    COLORMAP_HSV = 9, //!< 
    COLORMAP_PINK = 10, //!< 
    COLORMAP_HOT = 11, //!< 
    COLORMAP_PARULA = 12, //!< 
    COLORMAP_MAGMA = 13, //!< 
    COLORMAP_INFERNO = 14, //!< 
    COLORMAP_PLASMA = 15, //!< 
    COLORMAP_VIRIDIS = 16, //!< 
    COLORMAP_CIVIDIS = 17, //!< 
    COLORMAP_TWILIGHT = 18, //!< 
    COLORMAP_TWILIGHT_SHIFTED = 19 //!< 
};

It can be found in the definition colormap( Chromaticity diagram ) When , Enumeration used , So we can define a int Type to store 20 Kind of colormap.

The index of the array is from 0 At the beginning , So it is index%20, If it is index%21 You're going to report a mistake .

applyColormap() The first parameter of the function is the input image , The second parameter is the output image , The third parameter is the provided color map code value .（ Namely colormap Enumeration type in ）

applyColorMap() Function has another use ：

CV_EXPORTS_W void applyColorMap(InputArray src, OutputArray dst, InputArray userColor);

userColor： Custom colors （CV_8UC1 or CV_8UC3 and size 256）.

Result display ：

 over!!!