/**
* Discrete fourier transform 2d
*
* @param input the input to transform
* @param rows the number of rows in the transformed output matrix
* @param cols the number of columns in the transformed output matrix
* @return the discrete fourier transform of the input
*/
public static ComplexFloatMatrix complexDisceteFourierTransform(
FloatMatrix input, int rows, int cols) {
ComplexFloatMatrix base;
// pad
if (input.rows < rows || input.columns < cols)
base = MatrixUtil.complexPadWithZeros(input, rows, cols);
// truncation
else if (input.rows > rows || input.columns > cols) {
base = new ComplexFloatMatrix(input);
base =
base.get(
MatrixUtil.toIndices(RangeUtils.interval(0, rows)),
MatrixUtil.toIndices(RangeUtils.interval(0, cols)));
} else base = new ComplexFloatMatrix(input);
ComplexFloatMatrix temp = new ComplexFloatMatrix(base.rows, base.columns);
ComplexFloatMatrix ret = new ComplexFloatMatrix(base.rows, base.columns);
for (int i = 0; i < base.columns; i++) {
ComplexFloatMatrix column = base.getColumn(i);
temp.putColumn(i, complexDiscreteFourierTransform1d(column));
}
for (int i = 0; i < ret.rows; i++) {
ComplexFloatMatrix row = temp.getRow(i);
ret.putRow(i, complexDiscreteFourierTransform1d(row));
}
return ret;
}
public static FloatMatrix conv2d(FloatMatrix input, FloatMatrix kernel, Type type) {
FloatMatrix xShape = new FloatMatrix(1, 2);
xShape.put(0, input.rows);
xShape.put(1, input.columns);
FloatMatrix yShape = new FloatMatrix(1, 2);
yShape.put(0, kernel.rows);
yShape.put(1, kernel.columns);
FloatMatrix zShape = xShape.add(yShape).sub(1);
int retRows = (int) zShape.get(0);
int retCols = (int) zShape.get(1);
ComplexFloatMatrix fftInput = complexDisceteFourierTransform(input, retRows, retCols);
ComplexFloatMatrix fftKernel = complexDisceteFourierTransform(kernel, retRows, retCols);
ComplexFloatMatrix mul = fftKernel.mul(fftInput);
ComplexFloatMatrix retComplex = complexInverseDisceteFourierTransform(mul);
FloatMatrix ret = retComplex.getReal();
if (type == Type.VALID) {
FloatMatrix validShape = xShape.subi(yShape).add(1);
FloatMatrix start = zShape.sub(validShape).div(2);
FloatMatrix end = start.add(validShape);
if (start.get(0) < 1 || start.get(1) < 1)
throw new IllegalStateException("Illegal row index " + start);
if (end.get(0) < 1 || end.get(1) < 1)
throw new IllegalStateException("Illegal column index " + end);
ret =
ret.get(
RangeUtils.interval((int) start.get(0), (int) end.get(0)),
RangeUtils.interval((int) start.get(1), (int) end.get(1)));
}
return ret;
}