Convert an Image from one color space to another by using cvtcolor function

This opencv tutorial is about converting an image from one color space to that of the other using cvtcolor:

As the name suggests , cvtcolor converts an image from one color space to another.

Syntax of the code:

void cvtColor(InputArray src, OutputArray dst, int code, int dstCn=0 )

where

src   :– input image: 8-bit unsigned, 16-bit unsigned ( CV_16UC... ), or single-precision floating-point.

dst    :– output image of the same size and depth as src.

code  :– color space conversion code (see the description below).

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 .

As it has already been mentioned that the functions converts an image form one color space to another, there are various types of conversion possible.

Transformation	Syntax
RGB  GRAY	CV_RGB2GRAY
BGR  GRAY	CV_BGR2GRAY
GRAY  RGB	CV_GRAY2RGB
GRAY  BGR	CV_GRAY2BGR

Note:

The default color format in OpenCV is generally said 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.

Other Tranformations are:-

Transformation	Syntax
RGB  YCrCb	CV_RGB2YCrCb
BGR  YCrCb	CV_BGR2YCrCb
YCrCb  RGB	CV_YCrCb2RGB
YCrCb	CV_YCrCb2BGR

Transformation	Syntax
RGB  HSV	CV_RGB2HSV
BGR  HSV	CV_BGR2HSV
HSV RGB	CV_HSV2RGB
HSV BGR	CV_HSV2BGR

Transformation	Syntax
RGB  CIE L*a*b*	CV_RGB2Lab
BGR  CIE L*a*b*	CV_BGR2Lab
CIE L*a*b*  RGB	CV_Lab2RGB
CIE L*a*b*  BGR	CV_Lab2BGR

Transformation	Syntax
RGB  CIE L*u*v*	CV_RGB2Luv
BGR  CIE L*u*v*	CV_BGR2Luv
CIE L*u*v* RGB	CV_Luv2RGB
CIE L*u*v* BGR	CV_Luv2BGR

Transformation	Syntax
RGB  CIE XYZ	CV_RGB2XYZ
BGR  CIE XYZ	CV_BGR2XYZ
CIE XYZ RGB	CV_XYZ2RGB
CIE XYZ BGR	CV_XYZ2BGR

Opencv Code for color space conversion:

#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "iostream"

using namespace cv;

int main( )
{
// char* imageName = argv[1];

 Mat image;
 image = imread( "C:\\Users\\arjun\\Desktop\\color-image.png", 1 );

 Mat RGB2GRAY_image;
 cvtColor( image, RGB2GRAY_image, CV_RGB2GRAY );

 Mat BGR2GRAY_image;
 cvtColor( image, BGR2GRAY_image, CV_BGR2GRAY );

 Mat RGB2YCrCb_image;
 cvtColor( image, RGB2YCrCb_image, CV_RGB2YCrCb );

 Mat BGR2YCrCb_image;
 cvtColor( image, BGR2YCrCb_image, CV_BGR2YCrCb );

 Mat RGB2HSV_image;
 cvtColor( image, RGB2HSV_image, CV_RGB2HSV );

 Mat BGR2HSV_image;
 cvtColor( image, BGR2HSV_image, CV_BGR2HSV );

 Mat RGB2Lab_image;
 cvtColor( image, RGB2Lab_image, CV_RGB2Lab );

 Mat BGR2Lab_image;
 cvtColor( image, BGR2Lab_image, CV_BGR2Lab );

 Mat RGB2Luv_image;
 cvtColor( image, RGB2Luv_image, CV_RGB2Luv );

  Mat BGR2Luv_image;
 cvtColor( image, BGR2Luv_image, CV_BGR2Luv );

 Mat RGB2XYZ_image;
 cvtColor( image, RGB2XYZ_image, CV_RGB2XYZ );

 Mat BGR2XYZ_image;
 cvtColor( image, BGR2XYZ_image, CV_BGR2XYZ );

 namedWindow( "original image", CV_WINDOW_AUTOSIZE );
imshow( "original image", image );

namedWindow( "RGB2GRAY image", CV_WINDOW_AUTOSIZE );
imshow( "RGB2GRAY image",RGB2GRAY_image );
imwrite( "C:\\Users\\arjun\\Desktop\\RGB2GRAY.jpg", RGB2GRAY_image );

namedWindow( "BGR2GRAY image", CV_WINDOW_AUTOSIZE );
imshow( "BGR2GRAY image", BGR2GRAY_image );
imwrite( "C:\\Users\\arjun\\Desktop\\BGR2GRAY.jpg", BGR2GRAY_image );

namedWindow( "RGB2YCrCb image", CV_WINDOW_AUTOSIZE );
imshow( "RGB2YCrCb image", RGB2YCrCb_image );
imwrite( "C:\\Users\\arjun\\Desktop\\RGB2YCrCb.jpg", RGB2YCrCb_image );


namedWindow( "BGR2YCrCb image", CV_WINDOW_AUTOSIZE );
imshow( "BGR2YCrCb image", BGR2YCrCb_image );
imwrite( "C:\\Users\\arjun\\Desktop\\BGR2YCrCb.jpg", BGR2YCrCb_image );

namedWindow( "RGB2HSV image", CV_WINDOW_AUTOSIZE );
imshow( "RGB2HSV image", RGB2HSV_image );
imwrite( "C:\\Users\\arjun\\Desktop\\RGB2HSV.jpg", RGB2HSV_image );

namedWindow( "BGR2HSV image", CV_WINDOW_AUTOSIZE );
imshow( "BGR2HSV image", BGR2HSV_image );
imwrite( "C:\\Users\\arjun\\Desktop\\BGR2HSV.jpg", BGR2HSV_image );

namedWindow( "RGB2Lab image", CV_WINDOW_AUTOSIZE );
imshow( "RGB2Lab image", RGB2Lab_image );
imwrite( "C:\\Users\\arjun\\Desktop\\RGB2Lab.jpg", RGB2Lab_image );

namedWindow( "BGR2Lab image", CV_WINDOW_AUTOSIZE );
imshow( "BGR2Lab image", BGR2Lab_image );
imwrite( "C:\\Users\\arjun\\Desktop\\BGR2Lab.jpg", BGR2Lab_image );

namedWindow( "RGB2Luv image", CV_WINDOW_AUTOSIZE );
imshow( "RGB2Luv image", RGB2Luv_image );
imwrite( "C:\\Users\\arjun\\Desktop\\RGB2Luv.jpg", RGB2Luv_image );

namedWindow( "BGR2Luv image", CV_WINDOW_AUTOSIZE );
imshow( "BGR2Luv image", BGR2Luv_image );
imwrite( "C:\\Users\\arjun\\Desktop\\BGR2Luv.jpg", BGR2Luv_image );

namedWindow( "RGB2XYZ image", CV_WINDOW_AUTOSIZE );
imshow( "RGB2XYZ image", RGB2XYZ_image );
imwrite( "C:\\Users\\arjun\\Desktop\\RGB2XYZ.jpg", RGB2XYZ_image );

namedWindow( "BGR2XYZ image", CV_WINDOW_AUTOSIZE );
imshow( "BGR2XYZ image", BGR2XYZ_image );
imwrite( "C:\\Users\\arjun\\Desktop\\BGR2XYZ.jpg", BGR2XYZ_image );

 waitKey(0);

 return 0;
}

Original Image:

RGB2GRAY:

BGR2GRAY:

RGB2YCrCb:

BGR2YCrCb:

RGB2HSV:

BGR2HSV:

RGB2Lab:

BGR2Lab:

RGB2Luv:

BGR2Luv:

RGB2XYZ:

BGR2XYZ:

Here is the link of the opencv code:

https://drive.google.com/file/d/0B9Mnn6QWcwVnejJMeWotcExPWnc/view?usp=sharing

The Bayer pattern is widely used in CCD and CMOS cameras. It enables you to get color pictures from a single plane where R,G, and B pixels (sensors of a particular component) are interleaved.

Transformation	Syntax
BayerRG  RGB	CV_BayerRG2RGB
BayerRG  BGR	CV_BayerRG2BGR
BayerGB  RGB	CV_BayerGB2RGB
BayerGB  BGR	CV_BayerGB2BGR
BayerGR  RGB	CV_BayerGR2RGB
BayerGR  BGR	CV_BayerGR2BGR
BayerBG  RGB	CV_BayerBG2RGB
BayerBG  BGR	CV_BayerBG2BGR