If you are using a pair of NativeImageLoader from DataVec and opencv's imshow. You need to divide the matrix by 255(normalize) first else only a white image will appear. If you use opencv imread and imshow as a pair then there will be no problem.

NativeImageLoaderImshowPairExample.java

import org.datavec.image.loader.NativeImageLoader;
import org.nd4j.linalg.api.ndarray.INDArray;
import static org.bytedeco.opencv.global.opencv_highgui.*;

NativeImageLoader nil = new NativeImageLoader(416,416, 3);
INDArray image = nil.asMatrix("C:\\Users\\choowilson\\Desktop\\potato.jpg").div(255.0);
Mat mat = nil.asMat(image);
imshow("Output",mat);
waitKey(0);
destroyAllWindows();