/**
* Return a difference of gaussian image that measures the gradient at a scale defined by the two
* sigmas of the gaussians.
*
* @param image
* @param sigma1
* @param sigma2
* @return
*/
public Image<FloatType> getGradientImage() {
/*
* Create the DoG kernel.
*/
double[][] kernels1d1 = new double[input.getNumDimensions()][];
double[][] kernels1d2 = new double[input.getNumDimensions()][];
int[] kernelDimensions = input.createPositionArray();
int[] offset = input.createPositionArray();
for (int i = 0; i < kernels1d1.length; i++) {
kernels1d1[i] = Util.createGaussianKernel1DDouble(sigma1[i], true);
kernels1d2[i] = Util.createGaussianKernel1DDouble(sigma2[i], true);
kernelDimensions[i] = kernels1d1[i].length;
offset[i] = (kernels1d1[i].length - kernels1d2[i].length) / 2;
}
Image<FloatType> kernel = getFloatFactory().createImage(kernelDimensions);
LocalizableCursor<FloatType> kc = kernel.createLocalizableCursor();
int[] position = input.createPositionArray();
for (FloatType t : kc) {
kc.getPosition(position);
double value1 = 1;
double value2 = 1;
for (int i = 0; i < kernels1d1.length; i++) {
value1 *= kernels1d1[i][position[i]];
int position2 = position[i] - offset[i];
if ((position2 >= 0) && (position2 < kernels1d2[i].length)) {
value2 *= kernels1d2[i][position2];
} else {
value2 = 0;
}
}
t.setReal(value1 - value2);
}
kc.close();
/*
* Apply the kernel to the image.
*/
FourierConvolution<FloatType, FloatType> convolution =
new FourierConvolution<FloatType, FloatType>(getFloatImage(), kernel);
if (!convolution.process()) return null;
Image<FloatType> result = convolution.getResult();
/*
* Quantize the image.
*/
ComputeMinMax<FloatType> computeMinMax = new ComputeMinMax<FloatType>(result);
computeMinMax.process();
final float min = computeMinMax.getMin().get();
final float max = computeMinMax.getMax().get();
if (max == min) return result;
ImageConverter<FloatType, FloatType> quantizer =
new ImageConverter<FloatType, FloatType>(
result,
result.getImageFactory(),
new Converter<FloatType, FloatType>() {
@Override
public void convert(FloatType input, FloatType output) {
float value = (input.get() - min) / (max - min);
value = Math.round(value * 100);
output.set(value);
}
});
quantizer.process();
return quantizer.getResult();
}
