Add new "null" convolver

The new "null" convolver (implemented by the NULLConvolver class) does
no convolution, and instead returns the source image unmodified. This is
useful for testing Model overheads, like in the case of the "null"
profile.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>

docs/changelog.rst

@@ -5,6 +5,13 @@ Changelog
 .. highlight:: cpp
 .. namespace:: profit
 
+.. rubric:: Development version
+
+* A new ``null`` convolver has been added
+  that does no convolution
+  and simply returns the source image unmodified.
+  This is only useful for testing.
+
 .. rubric:: 1.9.3
 
 * A bug in the OpenCL implementation of the radial profiles

src/apps/profit-cli.cpp

@@ -215,6 +215,7 @@ The following convolver types are supported:
  * brute-old: An older, slower brute-force convolver (used only for comparisons)
  * opencl: An OpenCL-based brute-force convolver
  * fft: An FFT-based convolver
+ * null: A no-op convolver, useful for testing
 
 Profiles should be specified as follows (parts between [] are optional):
 

src/profit/convolve.cpp

@@ -518,6 +518,11 @@ Image OpenCLLocalConvolver::_clpadded_convolve(const Image &src, const Image &kr
 
 #endif // PROFIT_OPENCL
 
+Image NullConvolver::convolve_impl(const Image &src, const Image &krn, const Mask &mask, bool crop, Point &offset_out)
+{
+	return src;
+}
+
 ConvolverPtr create_convolver(const ConvolverType type, const ConvolverCreationPreferences &prefs)
 {
 	switch(type) {
@@ -553,6 +558,8 @@ ConvolverPtr create_convolver(const ConvolverType type, const ConvolverCreationP
 			                                      prefs.effort, prefs.omp_threads,
 			                                      prefs.reuse_krn_fft);
 #endif // PROFIT_FFTW
+		case NO_OP:
+			return std::make_shared<NullConvolver>();
 		default:
 			// Shouldn't happen
 			throw invalid_parameter("Unsupported convolver type: " + std::to_string(type));
@@ -577,6 +584,9 @@ ConvolverPtr create_convolver(const std::string &type, const ConvolverCreationPr
 		return create_convolver(FFT, prefs);
 	}
 #endif // PROFIT_FFTW
+	else if (type == "null") {
+		return create_convolver(NO_OP, prefs);
+	}
 
 	std::ostringstream os;
 	os << "Convolver of type " << type << " is not supported";

src/profit/convolve.h

@@ -54,6 +54,9 @@ enum ConvolverType {
 
 	/// @copydoc FFTConvolver
 	FFT,
+
+	/// @copydoc NULLConvolver
+	NO_OP
 };
 
 /**

src/profit/convolver_impl.h

@@ -187,4 +187,13 @@ class OpenCLLocalConvolver : public Convolver {
 
 #endif // PROFIT_OPENCL
 
+/**
+ * A convolver that doesn't convolve, useful for testing.
+ */
+class NullConvolver : public Convolver
+{
+public:
+	Image convolve_impl(const Image &src, const Image &krn, const Mask &mask, bool crop = true, Point &offset_out = NO_OFFSET) override;
+};
+
 }