deeplearning4j: Error when customizing PathLabelGenerator while setting up data pipeline for semantic segmentation

Issue Description

Hello guys, I am trying to implement semantic image segmentation with Unet network architecture, and i am having a hard time concerning how to set the data pipeline. I have managed to get the training data arranged in the following way:

• One directory in which i have the training images
• Another directory in which i put the labels (segmented images)
• I named the files in such a way that any image file in the training image directory has as corresponding label an image with same file name in the label directory.

Now i need to customize PathLabelGenerator to map the input images to their corresponding label images, and i intend to link the data by file name, meaning i want to link any training image and its corresponding label by making them have the same file name.

Here is my customized PathLabelGenerator code which i called CustomPathLabelGenerator:

public class CustomPathLabelGenerator implements org.datavec.api.io.labels.PathLabelGenerator {

	public CustomPathLabelGenerator() {
		
	}
	
	NativeImageLoader imageLoader = new NativeImageLoader(512, 512, 3);
	File labelsDir = new File(System.getProperty("user.dir"), "/src/main/resources/data/trainLabels/");
	
	public Writable getLabelForPath(String path) {
		
		NDArrayWritable ndArrayWritable = null;
		try {
			Collection<File> files = FileUtils.listFiles(labelsDir, null, true);
			for(Iterator<File> iter = files.iterator(); iter.hasNext();) {
				File file = (File) iter.next();
				if(file.getName().equals(new File(path).getName())) {
					ndArrayWritable = new NDArrayWritable(imageLoader.asMatrix(new File(path).getName()));
				}
			}					
		}catch (Exception e) {
			e.printStackTrace();
		}
		
		return ndArrayWritable;
	}
	
	public Writable getLabelForPath(URI uri) {
		System.out.println("URL in first getLabelForPath function: " + new File(uri).toString());
		return getLabelForPath(new File(uri).toString());
	}
	
	public boolean inferLabelClasses() {
		return true;
	}
}

And here is my code for for the data pipeline:

CustomPathLabelGenerator labelMaker = new CustomPathLabelGenerator();
		File mainTrainDataPath = new File(System.getProperty("user.dir"), "/src/main/resources/data/trainData/");
		FileSplit trainFileSplit = new FileSplit(mainTrainDataPath, NativeImageLoader.ALLOWED_FORMATS, rng);
		int numExamples = toIntExact(trainFileSplit.length());
		RandomPathFilter trainPathFilter = new RandomPathFilter(rng, null, numExamples);
		InputSplit[] trainInputSplit = trainFileSplit.sample(trainPathFilter);
		InputSplit trainData = trainInputSplit[0];
        DataNormalization scaler = new ImagePreProcessingScaler(0, 1);
		ImageRecordReader trainRecordReader = new ImageRecordReader(height, width, channels, labelMaker); 
		trainRecordReader.initialize(trainData);

But i am having the following error while just trying to check if the mapping works well:

java.io.FileNotFoundException: train.tif (The system cannot find the file specified)
	at java.io.FileInputStream.open0(Native Method)
	at java.io.FileInputStream.open(Unknown Source)
	at java.io.FileInputStream.<init>(Unknown Source)
	at org.datavec.image.loader.NativeImageLoader.asMatrix(NativeImageLoader.java:231)
	at org.datavec.image.loader.NativeImageLoader.asMatrix(NativeImageLoader.java:226)
	at com.neuronalstructuressegmentation.CustomPathLabelGenerator.getLabelForPath(CustomPathLabelGenerator.java:43)
	at com.neuronalstructuressegmentation.CustomPathLabelGenerator.getLabelForPath(CustomPathLabelGenerator.java:56)
	at org.datavec.image.recordreader.BaseImageRecordReader.initialize(BaseImageRecordReader.java:143)
	at com.neuronalstructuressegmentation.Segmentation.execute(Segmentation.java:90)
	at com.neuronalstructuressegmentation.Segmentation.main(Segmentation.java:380)
Exception in thread "main" java.lang.NullPointerException
	at org.datavec.image.recordreader.BaseImageRecordReader.initialize(BaseImageRecordReader.java:143)
	at com.neuronalstructuressegmentation.Segmentation.execute(Segmentation.java:90)
	at com.neuronalstructuressegmentation.Segmentation.main(Segmentation.java:380)

I made sure that the files are present in the respective derectories.

I currently have no idea about the origin or the cause of this error.

Version Information

Please indicate relevant versions, including, if relevant:

• Deeplearning4j version 1.0.0-beta3
• Platform information windows 8.1