feat: port image segmentation native code to C++ (#313)

## Description

Port image segmentation native code to C++.

### Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] Documentation update (improves or adds clarity to existing
documentation)

### Tested on

- [x] iOS
- [x] Android

### Related issues

#256 #255

### Checklist

- [x] I have performed a self-review of my code
- [x] I have commented my code, particularly in hard-to-understand areas
- [ ] I have updated the documentation accordingly
- [x] My changes generate no new warnings

---------

Co-authored-by: Mateusz Sluszniak <56299341+msluszniak@users.noreply.github.com>

Author: JakubGonera

android/src/main/java/com/swmansion/rnexecutorch/ImageSegmentation.kt

@@ -28,8 +28,6 @@ class RnExecutorchPackage : TurboReactPackage() {
       OCR(reactContext)
     } else if (name == VerticalOCR.NAME) {
       VerticalOCR(reactContext)
-    } else if (name == ImageSegmentation.NAME) {
-      ImageSegmentation(reactContext)
     } else if (name == ETInstaller.NAME) {
       ETInstaller(reactContext)
     } else if (name == Tokenizer.NAME) {
@@ -119,17 +117,6 @@ class RnExecutorchPackage : TurboReactPackage() {
           true,
         )
 
-      moduleInfos[ImageSegmentation.NAME] =
-        ReactModuleInfo(
-          ImageSegmentation.NAME,
-          ImageSegmentation.NAME,
-          false, // canOverrideExistingModule
-          false, // needsEagerInit
-          true, // hasConstants
-          false, // isCxxModule
-          true,
-        )
-
       moduleInfos[Tokenizer.NAME] =
         ReactModuleInfo(
           Tokenizer.NAME,

android/src/main/java/com/swmansion/rnexecutorch/RnExecutorchPackage.kt

@@ -1,6 +1,7 @@
 #include "RnExecutorchInstaller.h"
 
 #include <rnexecutorch/host_objects/JsiConversions.h>
+#include <rnexecutorch/models/image_segmentation/ImageSegmentation.h>
 #include <rnexecutorch/models/style_transfer/StyleTransfer.h>
 
 namespace rnexecutorch {
@@ -19,5 +20,10 @@ void RnExecutorchInstaller::injectJSIBindings(
       *jsiRuntime, "loadStyleTransfer",
       RnExecutorchInstaller::loadModel<StyleTransfer>(jsiRuntime, jsCallInvoker,
                                                       "loadStyleTransfer"));
+
+  jsiRuntime->global().setProperty(
+      *jsiRuntime, "loadImageSegmentation",
+      RnExecutorchInstaller::loadModel<ImageSegmentation>(
+          jsiRuntime, jsCallInvoker, "loadImageSegmentation"));
 }
 } // namespace rnexecutorch

android/src/main/java/com/swmansion/rnexecutorch/models/imageSegmentation/Constants.kt

@@ -49,7 +49,7 @@ class RnExecutorchInstaller {
                 jsiconversion::getValue<std::string>(args[0], runtime);
 
             auto modelImplementationPtr =
-                std::make_shared<ModelT>(source, &runtime);
+                std::make_shared<ModelT>(source, jsCallInvoker);
             auto modelHostObject = std::make_shared<ModelHostObject<ModelT>>(
                 modelImplementationPtr, jsCallInvoker);
 

android/src/main/java/com/swmansion/rnexecutorch/models/imageSegmentation/ImageSegmentationModel.kt

@@ -0,0 +1,19 @@
+#include "Numerical.h"
+
+#include <algorithm>
+#include <numeric>
+
+namespace rnexecutorch::numerical {
+void softmax(std::vector<float> &v) {
+  float max = *std::max_element(v.begin(), v.end());
+
+  float sum = 0.0f;
+  for (float &x : v) {
+    x = std::exp(x - max);
+    sum += x;
+  }
+  for (float &x : v) {
+    x /= sum;
+  }
+}
+} // namespace rnexecutorch::numerical

common/rnexecutorch/RnExecutorchInstaller.cpp

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <vector>
+
+namespace rnexecutorch::numerical {
+void softmax(std::vector<float> &v);
+} // namespace rnexecutorch::numerical

common/rnexecutorch/RnExecutorchInstaller.h

@@ -1,8 +1,10 @@
 #pragma once
 
-#include <jsi/jsi.h>
+#include <set>
 #include <type_traits>
 
+#include <jsi/jsi.h>
+
 namespace rnexecutorch::jsiconversion {
 
 using namespace facebook;
@@ -43,19 +45,33 @@ getValue<std::vector<std::string>>(const jsi::Value &val,
   return result;
 }
 
+// C++ set from JS array. Set with heterogenerous look-up (adding std::less<>
+// enables querying with std::string_view).
+template <>
+inline std::set<std::string, std::less<>>
+getValue<std::set<std::string, std::less<>>>(const jsi::Value &val,
+                                             jsi::Runtime &runtime) {
+
+  jsi::Array array = val.asObject(runtime).asArray(runtime);
+  size_t length = array.size(runtime);
+  std::set<std::string, std::less<>> result;
+
+  for (size_t i = 0; i < length; ++i) {
+    jsi::Value element = array.getValueAtIndex(runtime, i);
+    result.insert(getValue<std::string>(element, runtime));
+  }
+  return result;
+}
+
 // Conversion from C++ types to jsi --------------------------------------------
 
 // Implementation functions might return any type, but in a promise we can only
 // return jsi::Value or jsi::Object. For each type being returned
 // we add a function here.
 
-// Identity function for the sake of completeness
-inline jsi::Value getJsiValue(jsi::Value &&value, jsi::Runtime &runtime) {
-  return std::move(value);
-}
-
-inline jsi::Value getJsiValue(jsi::Object &&value, jsi::Runtime &runtime) {
-  return jsi::Value(std::move(value));
+inline jsi::Value getJsiValue(std::shared_ptr<jsi::Object> valuePtr,
+                              jsi::Runtime &runtime) {
+  return std::move(*valuePtr);
 }
 
 inline jsi::Value getJsiValue(const std::string &str, jsi::Runtime &runtime) {

common/rnexecutorch/data_processing/Numerical.cpp

@@ -55,9 +55,10 @@ template <typename Model> class ModelHostObject : public JsiHostObject {
               try {
                 auto result =
                     std::apply(std::bind_front(FnPtr, model), argsConverted);
-
-                callInvoker->invokeAsync([promise, result = std::move(result)](
-                                             jsi::Runtime &runtime) {
+                // The result is copied. It should either be quickly copiable,
+                // or passed with a shared_ptr.
+                callInvoker->invokeAsync([promise,
+                                          result](jsi::Runtime &runtime) {
                   promise->resolve(
                       jsiconversion::getJsiValue(std::move(result), runtime));
                 });