從舊版自訂模型 API 遷移

Firebase/MLModelInterpreter 程式庫 0.20.0 版推出新的 getLatestModelFilePath() 方法，可取得裝置上自訂模型的位置。您可以使用這個方法直接例項化 TensorFlow Lite Interpreter 物件，取代 Firebase 的 ModelInterpreter 包裝函式。

今後建議採用這種做法。由於 TensorFlow Lite 解譯器版本不再與 Firebase 程式庫版本連結，因此您可以更彈性地升級至新版 TensorFlow Lite，或更輕鬆地使用自訂 TensorFlow Lite 建構版本。

本頁面說明如何從使用 ModelInterpreter 遷移至 TensorFlow Lite Interpreter。

1. 更新專案依附元件

更新專案的 Podfile，加入 Firebase/MLModelInterpreter 程式庫 0.20.0 版 (或更新版本) 和 TensorFlow Lite 程式庫：

之前

Swift

pod 'Firebase/MLModelInterpreter', '0.19.0'

Objective-C

pod 'Firebase/MLModelInterpreter', '0.19.0'

晚於

Swift

pod 'Firebase/MLModelInterpreter', '~> 0.20.0'
pod 'TensorFlowLiteSwift'

Objective-C

pod 'Firebase/MLModelInterpreter', '~> 0.20.0'
pod 'TensorFlowLiteObjC'

2. 建立 TensorFlow Lite 解譯器，而非 Firebase ModelInterpreter

不必建立 Firebase ModelInterpreter，只要使用 getLatestModelFilePath() 取得裝置上的模型位置，並用來建立 TensorFlow Lite Interpreter 即可。

之前

Swift

let remoteModel = CustomRemoteModel(
    name: "your_remote_model"  // The name you assigned in the Firebase console.
)
interpreter = ModelInterpreter.modelInterpreter(remoteModel: remoteModel)

Objective-C

// Initialize using the name you assigned in the Firebase console.
FIRCustomRemoteModel *remoteModel =
        [[FIRCustomRemoteModel alloc] initWithName:@"your_remote_model"];
interpreter = [FIRModelInterpreter modelInterpreterForRemoteModel:remoteModel];

晚於

Swift

let remoteModel = CustomRemoteModel(
    name: "your_remote_model"  // The name you assigned in the Firebase console.
)
ModelManager.modelManager().getLatestModelFilePath(remoteModel) { (remoteModelPath, error) in
    guard error == nil, let remoteModelPath = remoteModelPath else { return }
    do {
        interpreter = try Interpreter(modelPath: remoteModelPath)
    } catch {
        // Error?
    }
}

Objective-C

FIRCustomRemoteModel *remoteModel =
        [[FIRCustomRemoteModel alloc] initWithName:@"your_remote_model"];
[[FIRModelManager modelManager] getLatestModelFilePath:remoteModel
                                            completion:^(NSString * _Nullable filePath,
                                                         NSError * _Nullable error) {
    if (error != nil || filePath == nil) { return; }

    NSError *tfError = nil;
    interpreter = [[TFLInterpreter alloc] initWithModelPath:filePath error:&tfError];
}];

3. 更新輸入和輸出準備程式碼

使用 ModelInterpreter 時，您可以在執行解譯器時傳遞 ModelInputOutputOptions 物件，指定模型的輸入和輸出形狀。

如果是 TensorFlow Lite 解譯器，您要改為呼叫 allocateTensors()，為模型的輸入和輸出分配空間，然後將輸入資料複製到輸入張量。

舉例來說，如果模型的輸入形狀為 [1 224 224 3] float 值，輸出形狀為 [1 1000] float 值，請進行下列變更：

之前

Swift

let ioOptions = ModelInputOutputOptions()
do {
    try ioOptions.setInputFormat(
        index: 0,
        type: .float32,
        dimensions: [1, 224, 224, 3]
    )
    try ioOptions.setOutputFormat(
        index: 0,
        type: .float32,
        dimensions: [1, 1000]
    )
} catch let error as NSError {
    print("Failed to set input or output format with error: \(error.localizedDescription)")
}

let inputs = ModelInputs()
do {
    let inputData = Data()
    // Then populate with input data.

    try inputs.addInput(inputData)
} catch let error {
    print("Failed to add input: \(error)")
}

interpreter.run(inputs: inputs, options: ioOptions) { outputs, error in
    guard error == nil, let outputs = outputs else { return }
    // Process outputs
    // ...
}

Objective-C

FIRModelInputOutputOptions *ioOptions = [[FIRModelInputOutputOptions alloc] init];
NSError *error;
[ioOptions setInputFormatForIndex:0
                             type:FIRModelElementTypeFloat32
                       dimensions:@[@1, @224, @224, @3]
                            error:&error];
if (error != nil) { return; }
[ioOptions setOutputFormatForIndex:0
                              type:FIRModelElementTypeFloat32
                        dimensions:@[@1, @1000]
                             error:&error];
if (error != nil) { return; }

FIRModelInputs *inputs = [[FIRModelInputs alloc] init];
NSMutableData *inputData = [[NSMutableData alloc] initWithCapacity:0];
// Then populate with input data.

[inputs addInput:inputData error:&error];
if (error != nil) { return; }

[interpreter runWithInputs:inputs
                   options:ioOptions
                completion:^(FIRModelOutputs * _Nullable outputs,
                             NSError * _Nullable error) {
  if (error != nil || outputs == nil) {
    return;
  }
  // Process outputs
  // ...
}];

晚於

Swift

do {
    try interpreter.allocateTensors()

    let inputData = Data()
    // Then populate with input data.

    try interpreter.copy(inputData, toInputAt: 0)

    try interpreter.invoke()
} catch let err {
    print(err.localizedDescription)
}

Objective-C

NSError *error = nil;

[interpreter allocateTensorsWithError:&error];
if (error != nil) { return; }

TFLTensor *input = [interpreter inputTensorAtIndex:0 error:&error];
if (error != nil) { return; }

NSMutableData *inputData = [[NSMutableData alloc] initWithCapacity:0];
// Then populate with input data.

[input copyData:inputData error:&error];
if (error != nil) { return; }

[interpreter invokeWithError:&error];
if (error != nil) { return; }

4. 更新輸出處理程式碼

最後，請從解譯器取得輸出張量，並將資料轉換為適合用途的結構，而不是使用 ModelOutputs 物件的 output() 方法取得模型輸出內容。

舉例來說，如果您要進行分類，可以進行下列變更：

之前

Swift

let output = try? outputs.output(index: 0) as? [[NSNumber]]
let probabilities = output?[0]

guard let labelPath = Bundle.main.path(
    forResource: "custom_labels",
    ofType: "txt"
) else { return }
let fileContents = try? String(contentsOfFile: labelPath)
guard let labels = fileContents?.components(separatedBy: "\n") else { return }

for i in 0 ..< labels.count {
    if let probability = probabilities?[i] {
        print("\(labels[i]): \(probability)")
    }
}

Objective-C

// Get first and only output of inference with a batch size of 1
NSError *error;
NSArray *probabilites = [outputs outputAtIndex:0 error:&error][0];
if (error != nil) { return; }

NSString *labelPath = [NSBundle.mainBundle pathForResource:@"retrained_labels"
                                                    ofType:@"txt"];
NSString *fileContents = [NSString stringWithContentsOfFile:labelPath
                                                   encoding:NSUTF8StringEncoding
                                                      error:&error];
if (error != nil || fileContents == NULL) { return; }
NSArray<NSString *> *labels = [fileContents componentsSeparatedByString:@"\n"];
for (int i = 0; i < labels.count; i++) {
    NSString *label = labels[i];
    NSNumber *probability = probabilites[i];
    NSLog(@"%@: %f", label, probability.floatValue);
}

晚於

Swift

do {
    // After calling interpreter.invoke():
    let output = try interpreter.output(at: 0)
    let probabilities =
            UnsafeMutableBufferPointer<Float32>.allocate(capacity: 1000)
    output.data.copyBytes(to: probabilities)

    guard let labelPath = Bundle.main.path(
        forResource: "custom_labels",
        ofType: "txt"
    ) else { return }
    let fileContents = try? String(contentsOfFile: labelPath)
    guard let labels = fileContents?.components(separatedBy: "\n") else { return }

    for i in labels.indices {
        print("\(labels[i]): \(probabilities[i])")
    }
} catch let err {
    print(err.localizedDescription)
}

Objective-C

NSError *error = nil;

TFLTensor *output = [interpreter outputTensorAtIndex:0 error:&error];
if (error != nil) { return; }

NSData *outputData = [output dataWithError:&error];
if (error != nil) { return; }

Float32 probabilities[outputData.length / 4];
[outputData getBytes:&probabilities length:outputData.length];

NSString *labelPath = [NSBundle.mainBundle pathForResource:@"custom_labels"
                                                    ofType:@"txt"];
NSString *fileContents = [NSString stringWithContentsOfFile:labelPath
                                                   encoding:NSUTF8StringEncoding
                                                      error:&error];
if (error != nil || fileContents == nil) { return; }

NSArray<NSString *> *labels = [fileContents componentsSeparatedByString:@"\n"];
for (int i = 0; i < labels.count; i++) {
    NSLog(@"%@: %f", labels[i], probabilities[i]);
}