CCP4: Add library to save MTZs

tools/jfjoch_process.cpp

@@ -25,6 +25,7 @@
 #include "../receiver/JFJochReceiverPlots.h"
 #include "../compression/JFJochCompressor.h"
 #include "../image_analysis/scale_merge/FrenchWilson.h"
+#include "../image_analysis/scale_merge/MtzWriter.h"
 
 void print_usage(Logger &logger) {
     logger.Info("Usage ./jfjoch_analysis {<options>} <input.h5>");
@@ -426,10 +427,9 @@ int main(int argc, char **argv) {
                 }
             }
 
-            // --- French-Wilson: convert I → F ---
             {
                 FrenchWilsonOptions fw_opts;
-                fw_opts.acentric = true;   // typical for MX
+                fw_opts.acentric = true;
                 fw_opts.num_shells = 20;
 
                 auto fw = FrenchWilson(scale_result->merged, fw_opts);
@@ -448,6 +448,30 @@ int main(int argc, char **argv) {
                     fw_file.close();
                     logger.Info("French-Wilson: wrote {} amplitudes to {}", fw.size(), fw_path);
                 }
+
+                // --- Write MTZ files ---
+                MtzWriteOptions mtz_opts(experiment,
+                       rotation_indexer_ret.has_value()
+                           ? std::optional<UnitCell>(rotation_indexer_ret->lattice.GetUnitCell())
+                           : std::nullopt);
+
+                // Intensities MTZ
+                {
+                    const std::string mtz_i_path = output_prefix + "_scaled.mtz";
+                    if (WriteMtzIntensities(mtz_i_path, scale_result->merged, mtz_opts))
+                        logger.Info("Wrote {} reflections to {}", scale_result->merged.size(), mtz_i_path);
+                    else
+                        logger.Error("Failed to write {}", mtz_i_path);
+                }
+
+                // Amplitudes MTZ (French-Wilson)
+                {
+                    const std::string mtz_f_path = output_prefix + "_amplitudes.mtz";
+                    if (WriteMtzAmplitudes(mtz_f_path, fw, mtz_opts))
+                        logger.Info("Wrote {} reflections to {}", fw.size(), mtz_f_path);
+                    else
+                        logger.Error("Failed to write {}", mtz_f_path);
+                }
             }
         } else {
             logger.Warning("Scaling skipped — too few reflections accumulated (need >= 20)");