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A Flutter Plugin for Accessing TensorFlow Lite API, tflite

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What is tflite?

A Tensorflow model is converted to a Tensorflow Lite flat buffer file using Tensorflow Lite Converter (. tflite). The client, which in our instance is a mobile device operating on iOS or Android or an embedded device, receives the Tensorflow Lite flat buffer file.

tflite is a Flutter plugin for accessing TensorFlow Lite API. Supports image classification, object detection (SSD and YOLO), Pix2Pix and Deeplab and PoseNet on both iOS and Android.

Installation

Add tflite as a dependency in your pubspec.yaml file.

Android

In android/app/build.gradle, add the following setting in android block.

    aaptOptions {
        noCompress 'tflite'
        noCompress 'lite'
    }

iOS

Solutions to build errors on iOS:

  • ‘vector’ file not found”Open ios/Runner.xcworkspace in Xcode, click Runner > Tagets > Runner > Build Settings, search Compile Sources As, change the value to Objective-C++
  • ‘tensorflow/lite/kernels/register.h’ file not foundThe plugin assumes the tensorflow header files are located in path “tensorflow/lite/kernels”.However, for early versions of tensorflow the header path is “tensorflow/contrib/lite/kernels”.Use CONTRIB_PATH to toggle the path. Uncomment //#define CONTRIB_PATH from here: https://github.com/shaqian/flutter_tflite/blob/master/ios/Classes/TflitePlugin.mm#L1

Breaking changes

Since 1.1.0:

  1. iOS TensorFlow Lite library is upgraded from TensorFlowLite　1.x to TensorFlowLiteObjC　2.x. Changes to native code are denoted with TFLITE2.

Since 1.0.0:

  1. Updated to TensorFlow Lite API v1.12.0.
  2. No longer accepts parameter inputSize and numChannels. They will be retrieved from input tensor.
  3. numThreads is moved to Tflite.loadModel.

Usage

  1. Create a assets folder and place your label file and model file in it. In pubspec.yaml add:
  assets:
   - assets/labels.txt
   - assets/mobilenet_v1_1.0_224.tflite
  1. Import the library:
import 'package:tflite/tflite.dart';
  1. Load the model and labels:
String res = await Tflite.loadModel(
  model: "assets/mobilenet_v1_1.0_224.tflite",
  labels: "assets/labels.txt",
  numThreads: 1, // defaults to 1
  isAsset: true, // defaults to true, set to false to load resources outside assets
  useGpuDelegate: false // defaults to false, set to true to use GPU delegate
);
  1. See the section for the respective model below.
  2. Release resources:
await Tflite.close();

GPU Delegate

When using GPU delegate, refer to this step for release mode setting to get better performance.

Image Classification

  • Output format:
{
  index: 0,
  label: "person",
  confidence: 0.629
}
  • Run on image:
var recognitions = await Tflite.runModelOnImage(
  path: filepath,   // required
  imageMean: 0.0,   // defaults to 117.0
  imageStd: 255.0,  // defaults to 1.0
  numResults: 2,    // defaults to 5
  threshold: 0.2,   // defaults to 0.1
  asynch: true      // defaults to true
);
  • Run on binary:
var recognitions = await Tflite.runModelOnBinary(
  binary: imageToByteListFloat32(image, 224, 127.5, 127.5),// required
  numResults: 6,    // defaults to 5
  threshold: 0.05,  // defaults to 0.1
  asynch: true      // defaults to true
);

Uint8List imageToByteListFloat32(
    img.Image image, int inputSize, double mean, double std) {
  var convertedBytes = Float32List(1 * inputSize * inputSize * 3);
  var buffer = Float32List.view(convertedBytes.buffer);
  int pixelIndex = 0;
  for (var i = 0; i < inputSize; i++) {
    for (var j = 0; j < inputSize; j++) {
      var pixel = image.getPixel(j, i);
      buffer[pixelIndex++] = (img.getRed(pixel) - mean) / std;
      buffer[pixelIndex++] = (img.getGreen(pixel) - mean) / std;
      buffer[pixelIndex++] = (img.getBlue(pixel) - mean) / std;
    }
  }
  return convertedBytes.buffer.asUint8List();
}

Uint8List imageToByteListUint8(img.Image image, int inputSize) {
  var convertedBytes = Uint8List(1 * inputSize * inputSize * 3);
  var buffer = Uint8List.view(convertedBytes.buffer);
  int pixelIndex = 0;
  for (var i = 0; i < inputSize; i++) {
    for (var j = 0; j < inputSize; j++) {
      var pixel = image.getPixel(j, i);
      buffer[pixelIndex++] = img.getRed(pixel);
      buffer[pixelIndex++] = img.getGreen(pixel);
      buffer[pixelIndex++] = img.getBlue(pixel);
    }
  }
  return convertedBytes.buffer.asUint8List();
}
  • Run on image stream (video frame):

Works with camera plugin 4.0.0. Video format: (iOS) kCVPixelFormatType_32BGRA, (Android) YUV_420_888.

var recognitions = await Tflite.runModelOnFrame(
  bytesList: img.planes.map((plane) {return plane.bytes;}).toList(),// required
  imageHeight: img.height,
  imageWidth: img.width,
  imageMean: 127.5,   // defaults to 127.5
  imageStd: 127.5,    // defaults to 127.5
  rotation: 90,       // defaults to 90, Android only
  numResults: 2,      // defaults to 5
  threshold: 0.1,     // defaults to 0.1
  asynch: true        // defaults to true
);

Object Detection

  • Output format:

x, y, w, h are between [0, 1]. You can scale x, w by the width and y, h by the height of the image.

{
  detectedClass: "hot dog",
  confidenceInClass: 0.123,
  rect: {
    x: 0.15,
    y: 0.33,
    w: 0.80,
    h: 0.27
  }
}

SSD MobileNet:

  • Run on image:
var recognitions = await Tflite.detectObjectOnImage(
  path: filepath,       // required
  model: "SSDMobileNet",
  imageMean: 127.5,     
  imageStd: 127.5,      
  threshold: 0.4,       // defaults to 0.1
  numResultsPerClass: 2,// defaults to 5
  asynch: true          // defaults to true
);
  • Run on binary:
var recognitions = await Tflite.detectObjectOnBinary(
  binary: imageToByteListUint8(resizedImage, 300), // required
  model: "SSDMobileNet",  
  threshold: 0.4,                                  // defaults to 0.1
  numResultsPerClass: 2,                           // defaults to 5
  asynch: true                                     // defaults to true
);
  • Run on image stream (video frame):

Works with camera plugin 4.0.0. Video format: (iOS) kCVPixelFormatType_32BGRA, (Android) YUV_420_888.

var recognitions = await Tflite.detectObjectOnFrame(
  bytesList: img.planes.map((plane) {return plane.bytes;}).toList(),// required
  model: "SSDMobileNet",  
  imageHeight: img.height,
  imageWidth: img.width,
  imageMean: 127.5,   // defaults to 127.5
  imageStd: 127.5,    // defaults to 127.5
  rotation: 90,       // defaults to 90, Android only
  numResults: 2,      // defaults to 5
  threshold: 0.1,     // defaults to 0.1
  asynch: true        // defaults to true
);

Tiny YOLOv2:

  • Run on image:
var recognitions = await Tflite.detectObjectOnImage(
  path: filepath,       // required
  model: "YOLO",      
  imageMean: 0.0,       
  imageStd: 255.0,      
  threshold: 0.3,       // defaults to 0.1
  numResultsPerClass: 2,// defaults to 5
  anchors: anchors,     // defaults to [0.57273,0.677385,1.87446,2.06253,3.33843,5.47434,7.88282,3.52778,9.77052,9.16828]
  blockSize: 32,        // defaults to 32
  numBoxesPerBlock: 5,  // defaults to 5
  asynch: true          // defaults to true
);
  • Run on binary:
var recognitions = await Tflite.detectObjectOnBinary(
  binary: imageToByteListFloat32(resizedImage, 416, 0.0, 255.0), // required
  model: "YOLO",  
  threshold: 0.3,       // defaults to 0.1
  numResultsPerClass: 2,// defaults to 5
  anchors: anchors,     // defaults to [0.57273,0.677385,1.87446,2.06253,3.33843,5.47434,7.88282,3.52778,9.77052,9.16828]
  blockSize: 32,        // defaults to 32
  numBoxesPerBlock: 5,  // defaults to 5
  asynch: true          // defaults to true
);
  • Run on image stream (video frame):

Works with camera plugin 4.0.0. Video format: (iOS) kCVPixelFormatType_32BGRA, (Android) YUV_420_888.

var recognitions = await Tflite.detectObjectOnFrame(
  bytesList: img.planes.map((plane) {return plane.bytes;}).toList(),// required
  model: "YOLO",  
  imageHeight: img.height,
  imageWidth: img.width,
  imageMean: 0,         // defaults to 127.5
  imageStd: 255.0,      // defaults to 127.5
  numResults: 2,        // defaults to 5
  threshold: 0.1,       // defaults to 0.1
  numResultsPerClass: 2,// defaults to 5
  anchors: anchors,     // defaults to [0.57273,0.677385,1.87446,2.06253,3.33843,5.47434,7.88282,3.52778,9.77052,9.16828]
  blockSize: 32,        // defaults to 32
  numBoxesPerBlock: 5,  // defaults to 5
  asynch: true          // defaults to true
);

Pix2Pix

Thanks to RP from Green Appers

  • Output format:The output of Pix2Pix inference is Uint8List type. Depending on the outputType used, the output is:
    • (if outputType is png) byte array of a png image
    • (otherwise) byte array of the raw output
  • Run on image:
var result = await runPix2PixOnImage(
  path: filepath,       // required
  imageMean: 0.0,       // defaults to 0.0
  imageStd: 255.0,      // defaults to 255.0
  asynch: true      // defaults to true
);
  • Run on binary:
var result = await runPix2PixOnBinary(
  binary: binary,       // required
  asynch: true      // defaults to true
);
  • Run on image stream (video frame):
var result = await runPix2PixOnFrame(
  bytesList: img.planes.map((plane) {return plane.bytes;}).toList(),// required
  imageHeight: img.height, // defaults to 1280
  imageWidth: img.width,   // defaults to 720
  imageMean: 127.5,   // defaults to 0.0
  imageStd: 127.5,    // defaults to 255.0
  rotation: 90,       // defaults to 90, Android only
  asynch: true        // defaults to true
);

Deeplab

Thanks to RP from see– for Android implementation.

  • Output format:The output of Deeplab inference is Uint8List type. Depending on the outputType used, the output is:
    • (if outputType is png) byte array of a png image
    • (otherwise) byte array of r, g, b, a values of the pixels
  • Run on image:
var result = await runSegmentationOnImage(
  path: filepath,     // required
  imageMean: 0.0,     // defaults to 0.0
  imageStd: 255.0,    // defaults to 255.0
  labelColors: [...], // defaults to https://github.com/shaqian/flutter_tflite/blob/master/lib/tflite.dart#L219
  outputType: "png",  // defaults to "png"
  asynch: true        // defaults to true
);
  • Run on binary:
var result = await runSegmentationOnBinary(
  binary: binary,     // required
  labelColors: [...], // defaults to https://github.com/shaqian/flutter_tflite/blob/master/lib/tflite.dart#L219
  outputType: "png",  // defaults to "png"
  asynch: true        // defaults to true
);
  • Run on image stream (video frame):
var result = await runSegmentationOnFrame(
  bytesList: img.planes.map((plane) {return plane.bytes;}).toList(),// required
  imageHeight: img.height, // defaults to 1280
  imageWidth: img.width,   // defaults to 720
  imageMean: 127.5,        // defaults to 0.0
  imageStd: 127.5,         // defaults to 255.0
  rotation: 90,            // defaults to 90, Android only
  labelColors: [...],      // defaults to https://github.com/shaqian/flutter_tflite/blob/master/lib/tflite.dart#L219
  outputType: "png",       // defaults to "png"
  asynch: true             // defaults to true
);

PoseNet

Model is from StackOverflow thread.

  • Output format:

x, y are between [0, 1]. You can scale x by the width and y by the height of the image.

[ // array of poses/persons
  { // pose #1
    score: 0.6324902,
    keypoints: {
      0: {
        x: 0.250,
        y: 0.125,
        part: nose,
        score: 0.9971070
      },
      1: {
        x: 0.230,
        y: 0.105,
        part: leftEye,
        score: 0.9978438
      }
      ......
    }
  },
  { // pose #2
    score: 0.32534285,
    keypoints: {
      0: {
        x: 0.402,
        y: 0.538,
        part: nose,
        score: 0.8798978
      },
      1: {
        x: 0.380,
        y: 0.513,
        part: leftEye,
        score: 0.7090239
      }
      ......
    }
  },
  ......
]
  • Run on image:
var result = await runPoseNetOnImage(
  path: filepath,     // required
  imageMean: 125.0,   // defaults to 125.0
  imageStd: 125.0,    // defaults to 125.0
  numResults: 2,      // defaults to 5
  threshold: 0.7,     // defaults to 0.5
  nmsRadius: 10,      // defaults to 20
  asynch: true        // defaults to true
);
  • Run on binary:
var result = await runPoseNetOnBinary(
  binary: binary,     // required
  numResults: 2,      // defaults to 5
  threshold: 0.7,     // defaults to 0.5
  nmsRadius: 10,      // defaults to 20
  asynch: true        // defaults to true
);
  • Run on image stream (video frame):
var result = await runPoseNetOnFrame(
  bytesList: img.planes.map((plane) {return plane.bytes;}).toList(),// required
  imageHeight: img.height, // defaults to 1280
  imageWidth: img.width,   // defaults to 720
  imageMean: 125.0,        // defaults to 125.0
  imageStd: 125.0,         // defaults to 125.0
  rotation: 90,            // defaults to 90, Android only
  numResults: 2,           // defaults to 5
  threshold: 0.7,          // defaults to 0.5
  nmsRadius: 10,           // defaults to 20
  asynch: true             // defaults to true
);

Example

Prediction in Static Images

Refer to, Flutter Plugin tflite Example.

Real-time detection

Refer to, Real Time Object Detection in Flutter using camera and tflite Plugin.

Run test cases

flutter test test/tflite_test.dart

GitHub

Source Code: flutter_tflite.

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