Why the grayscale image has 1 channel but still need 'Vec3b' to access the pixel value? And why there should be 3 different values.
char* imageName = argv[1];
Mat image;
image = imread(imageName, 1);
if( argc != 2 || !image.data )
{
cout << " No image data \n ";
return -1;
}
cout << "original: " << image.at<Vec3b>(10,10) << endl;
cout << image.size() << " channels: " << image.channels() << endl;
Mat gray_image;
cvtColor( image, gray_image, COLOR_BGR2GRAY );
cout << "gray: " << gray_image.at<Vec3b>(10,10) << endl;
cout << gray_image.size() << " channels: " << gray_image.channels() << endl;
imwrite( "Gray_Image.jpg", gray_image );
The output looks as follows.
original: [110, 130, 225]
[220 x 220] channels: 3
gray: [94, 97, 98]
[220 x 220] channels: 1