Load image from jar.

I found this code and made some updates to it. It allows for easily loading an image from the package to a Mat. I haven't tested the part where it reverts to use JavaIO to load the bytes. The issue i think i was getting from loading images was a leading slash and this fixes that.

The constants for color v grey should probably be set with constants from JavaCv but i didn't want to dig thru source at that time. I'm not sure if you want to integrate this or if it's likely to break from updates, or if i may have missed this functionality somewhere else. Thank you.

//http://answers.opencv.org/question/10236/opencv-java-api-highguiimread-and-paths-pointing-to-files-in-a-jar/
//credit to Lucky Luke 
//i made some updates but i'm not sure about the JavaIO part 
//  as nothing i've loaded used that code yet

import org.bytedeco.javacpp.opencv_core.Mat;
import org.bytedeco.javacpp.indexer.ByteIndexer;

import static org.bytedeco.javacpp.opencv_imgcodecs.*;

import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;

public final class OpenCVUtils {
    private OpenCVUtils() {}
     /**
    * 8bit, 3-channel image.
    * @see Highgui.CV_LOAD_IMAGE_COLOR
    */
    public static final int LOAD_COLOR = 3;

    /**
    * 8bit, 1-channel image.
    * @see Highgui.CV_LOAD_IMAGE_GRAYSCALE
    */
    public static final int LOAD_GRAYSCALE = 1;

    public static Mat readImage(String name, int flags) {
        URL url = ClassLoader.getSystemResource(name);

        // make sure the file exists
        if (url == null) {
            System.out.println("ResourceNotFound: " + name);
            return new Mat();
        }

        String path = url.getPath();

        // not sure why we (sometimes; while running unpacked from the IDE) end 
        // up with the authority-part of the path (a single slash) as prefix,
        // ...anyways: Highgui.imread can't handle it, so that's why.
        if (path.startsWith("/")) {
            path = path.substring(1);
        }

        Mat image = imread(path,flags);
        if (image.empty()) {
            System.out.println("normal loading failed WHYYY???");
            BufferedImage buf;

            try {
                buf = ImageIO.read(url);
            } catch (IOException e) {
                System.out.println("IOException: " + e.getMessage());
                return image;
            }

            int height = buf.getHeight();
            int width = buf.getWidth();
            int rgb, type, channels;

            switch (flags) {
                case LOAD_GRAYSCALE:
                    type = CV_LOAD_IMAGE_GRAYSCALE;
                    channels = 1;
                    break;
                case LOAD_COLOR:
                default:
                    type = CV_LOAD_IMAGE_COLOR;
                    channels = 3;
                    break;
            }

            byte[] px = new byte[channels];
            image = new Mat(height, width, type);
            ByteIndexer bi = image.createIndexer();


            for (int y=0; y<height; y++) {
                for (int x=0; x<width; x++) {
                    rgb = buf.getRGB(x, y);
                    px[0] = (byte)(rgb & 0xFF);
                    if (channels==3) {
                        px[1] = (byte)((rgb >> 8) & 0xFF);
                        px[2] = (byte)((rgb >> 16) & 0xFF);
                    }
                    bi.put(y, x, px);

                }
            }            
        }

        return image;

    }

    public static Mat readImage(String name) {
        return readImage(name, LOAD_COLOR);
    }

}