Added iOS language detector implementation

mediapipe/tasks/ios/text/language_detector/BUILD

@@ -31,3 +31,28 @@ objc_library(
         "//mediapipe/tasks/ios/core:MPPTaskResult",
     ],
 )
+
+objc_library(
+    name = "MPPLanguageDetector",
+    srcs = ["sources/MPPLanguageDetector.mm"],
+    hdrs = ["sources/MPPLanguageDetector.h"],
+    copts = [
+        "-ObjC++",
+        "-std=c++17",
+        "-x objective-c++",
+    ],
+    module_name = "MPPLanguageDetector",
+    deps = [
+        ":MPPLanguageDetectorOptions",
+        ":MPPLanguageDetectorResult",
+        "//mediapipe/tasks/cc/text/text_classifier:text_classifier_graph",
+        "//mediapipe/tasks/ios/common/utils:MPPCommonUtils",
+        "//mediapipe/tasks/ios/common/utils:NSStringHelpers",
+        "//mediapipe/tasks/ios/core:MPPTaskInfo",
+        "//mediapipe/tasks/ios/core:MPPTaskOptions",
+        "//mediapipe/tasks/ios/core:MPPTextPacketCreator",
+        "//mediapipe/tasks/ios/text/core:MPPTextTaskRunner",
+        "//mediapipe/tasks/ios/text/language_detector/utils:MPPLanguageDetectorOptionsHelpers",
+        "//mediapipe/tasks/ios/text/language_detector/utils:MPPLanguageDetectorResultHelpers",
+    ],
+)

mediapipe/tasks/ios/text/language_detector/sources/MPPLanguageDetector.h

@@ -0,0 +1,88 @@
+// Copyright 2023 The MediaPipe Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "mediapipe/tasks/ios/core/sources/MPPTaskOptions.h"
+#import "mediapipe/tasks/ios/text/language_detector/sources/MPPLanguageDetectorOptions.h"
+#import "mediapipe/tasks/ios/text/language_detector/sources/MPPLanguageDetectorResult.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * @brief Predicts the language of an input text.
+ *
+ * This API expects a TFLite model with [TFLite Model
+ * Metadata](https://www.tensorflow.org/lite/convert/metadata")that contains the mandatory
+ * (described below) input tensor, output tensor, and the language codes in an AssociatedFile.
+ *
+ * Metadata is required for models with int32 input tensors because it contains the input
+ * process unit for the model's Tokenizer. No metadata is required for models with string
+ * input tensors.
+ *
+ * Input tensor
+ *  - One input tensor (`kTfLiteString`) of shape `[1]` containing the input string.
+ *
+ * Output tensor
+ *  - One output tensor (`kTfLiteFloat32`) of shape `[1 x N]` where `N` is the number of languages.
+ */
+NS_SWIFT_NAME(LanguageDetector)
+@interface MPPLanguageDetector : NSObject
+
+/**
+ * Creates a new instance of `LanguageDetector` from an absolute path to a TensorFlow Lite
+ * model file stored locally on the device and the default `LanguageDetectorOptions`.
+ *
+ * @param modelPath An absolute path to a TensorFlow Lite model file stored locally on the device.
+ * @param error An optional error parameter populated when there is an error in initializing the
+ * language detector.
+ *
+ * @return A new instance of `LanguageDetector` with the given model path. `nil` if there is an
+ * error in initializing the language detector.
+ */
+- (nullable instancetype)initWithModelPath:(NSString *)modelPath error:(NSError **)error;
+
+/**
+ * Creates a new instance of `LanguageDetector` from the given `LanguageDetectorOptions`.
+ *
+ * @param options The options of type `LanguageDetectorOptions` to use for configuring the
+ * `LanguageDetector`.
+ * @param error An optional error parameter populated when there is an error in initializing the
+ * language detector.
+ *
+ * @return A new instance of `LanguageDetector` with the given options. `nil` if there is an
+ * error in initializing the language detector.
+ */
+- (nullable instancetype)initWithOptions:(MPPLanguageDetectorOptions *)options
+                                   error:(NSError **)error NS_DESIGNATED_INITIALIZER;
+
+/**
+ * Predicts the language of the input text.
+ *
+ * @param text The `NSString` for which language is to be predicted.
+ * @param error An optional error parameter populated when there is an error in performing
+ * language prediction on the input text.
+ *
+ * @return  A `LanguageDetectorResult` object that contains a list of language predictions.
+ */
+- (nullable MPPLanguageDetectorResult *)detectText:(NSString *)text
+                                             error:(NSError **)error NS_SWIFT_NAME(detect(text:));
+
+- (instancetype)init NS_UNAVAILABLE;
+
++ (instancetype)new NS_UNAVAILABLE;
+
+@end
+
+NS_ASSUME_NONNULL_END

mediapipe/tasks/ios/text/language_detector/sources/MPPLanguageDetector.mm

@@ -0,0 +1,96 @@
+// Copyright 2023 The MediaPipe Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "mediapipe/tasks/ios/text/language_detector/sources/MPPLanguageDetector.h"
+
+#import "mediapipe/tasks/ios/common/utils/sources/MPPCommonUtils.h"
+#import "mediapipe/tasks/ios/common/utils/sources/NSString+Helpers.h"
+#import "mediapipe/tasks/ios/core/sources/MPPTaskInfo.h"
+#import "mediapipe/tasks/ios/core/sources/MPPTextPacketCreator.h"
+#import "mediapipe/tasks/ios/text/core/sources/MPPTextTaskRunner.h"
+#import "mediapipe/tasks/ios/text/language_detector/utils/sources/MPPLanguageDetectorOptions+Helpers.h"
+#import "mediapipe/tasks/ios/text/language_detector/utils/sources/MPPLanguageDetectorResult+Helpers.h"
+
+namespace {
+using ::mediapipe::Packet;
+using ::mediapipe::tasks::core::PacketMap;
+}  // namespace
+
+static NSString *const kClassificationsStreamName = @"classifications_out";
+static NSString *const kClassificationsTag = @"CLASSIFICATIONS";
+static NSString *const kTextInStreamName = @"text_in";
+static NSString *const kTextTag = @"TEXT";
+static NSString *const kTaskGraphName =
+    @"mediapipe.tasks.text.language_detector.LanguageDetectorGraph";
+
+@interface MPPLanguageDetector () {
+  /** iOS Text Task Runner */
+  MPPTextTaskRunner *_textTaskRunner;
+}
+@end
+
+@implementation MPPLanguageDetector
+
+- (instancetype)initWithOptions:(MPPLanguageDetectorOptions *)options error:(NSError **)error {
+  self = [super init];
+  if (self) {
+    MPPTaskInfo *taskInfo = [[MPPTaskInfo alloc]
+        initWithTaskGraphName:kTaskGraphName
+                 inputStreams:@[ [NSString stringWithFormat:@"%@:%@", kTextTag, kTextInStreamName] ]
+                outputStreams:@[ [NSString stringWithFormat:@"%@:%@", kClassificationsTag,
+                                                            kClassificationsStreamName] ]
+                  taskOptions:options
+           enableFlowLimiting:NO
+                        error:error];
+
+    if (!taskInfo) {
+      return nil;
+    }
+
+    _textTaskRunner =
+        [[MPPTextTaskRunner alloc] initWithCalculatorGraphConfig:[taskInfo generateGraphConfig]
+                                                           error:error];
+
+    if (!_textTaskRunner) {
+      return nil;
+    }
+  }
+  return self;
+}
+
+- (instancetype)initWithModelPath:(NSString *)modelPath error:(NSError **)error {
+  MPPLanguageDetectorOptions *options = [[MPPLanguageDetectorOptions alloc] init];
+
+  options.baseOptions.modelAssetPath = modelPath;
+
+  return [self initWithOptions:options error:error];
+}
+
+- (nullable MPPLanguageDetectorResult *)detectText:(NSString *)text error:(NSError **)error {
+  Packet packet = [MPPTextPacketCreator createWithText:text];
+
+  std::map<std::string, Packet> packetMap = {{kTextInStreamName.cppString, packet}};
+  std::optional<PacketMap> outputPacketMap = [_textTaskRunner processPacketMap:packetMap
+                                                                         error:error];
+
+  if (!outputPacketMap.has_value()) {
+    return nil;
+  }
+
+  return
+      [MPPLanguageDetectorResult languageDetectorResultWithClassificationsPacket:
+                                     outputPacketMap.value()[kClassificationsStreamName.cppString]];
+}
+
+@end