packages/firebase_ml_vision/ios/Classes/FirebaseMlVisionPlugin.m

#import "FirebaseMlVisionPlugin.h"
#import "UserAgent.h"

static FlutterError *getFlutterError(NSError *error) {
  return [FlutterError errorWithCode:[NSString stringWithFormat:@"Error %d", (int)error.code]
                             message:error.domain
                             details:error.localizedDescription];
}

@implementation FLTFirebaseMlVisionPlugin
static NSMutableDictionary<NSNumber *, id<Detector>> *detectors;

+ (void)handleError:(NSError *)error result:(FlutterResult)result {
  result(getFlutterError(error));
}

+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
  detectors = [NSMutableDictionary new];
  FlutterMethodChannel *channel =
      [FlutterMethodChannel methodChannelWithName:@"plugins.flutter.io/firebase_ml_vision"
                                  binaryMessenger:[registrar messenger]];
  FLTFirebaseMlVisionPlugin *instance = [[FLTFirebaseMlVisionPlugin alloc] init];
  [registrar addMethodCallDelegate:instance channel:channel];

  SEL sel = NSSelectorFromString(@"registerLibrary:withVersion:");
  if ([FIRApp respondsToSelector:sel]) {
    [FIRApp performSelector:sel withObject:LIBRARY_NAME withObject:LIBRARY_VERSION];
  }
}

- (instancetype)init {
  self = [super init];
  if (self) {
    if (![FIRApp appNamed:@"__FIRAPP_DEFAULT"]) {
      NSLog(@"Configuring the default Firebase app...");
      [FIRApp configure];
      NSLog(@"Configured the default Firebase app %@.", [FIRApp defaultApp].name);
    }
  }
  return self;
}

- (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
  if ([@"BarcodeDetector#detectInImage" isEqualToString:call.method] ||
      [@"FaceDetector#processImage" isEqualToString:call.method] ||
      [@"ImageLabeler#processImage" isEqualToString:call.method] ||
      [@"TextRecognizer#processImage" isEqualToString:call.method]) {
    [self handleDetection:call result:result];
  } else if ([@"BarcodeDetector#close" isEqualToString:call.method] ||
             [@"FaceDetector#close" isEqualToString:call.method] ||
             [@"ImageLabeler#close" isEqualToString:call.method] ||
             [@"TextRecognizer#close" isEqualToString:call.method]) {
    NSNumber *handle = call.arguments[@"handle"];
    [detectors removeObjectForKey:handle];
    result(nil);
  } else {
    result(FlutterMethodNotImplemented);
  }
}

- (void)handleDetection:(FlutterMethodCall *)call result:(FlutterResult)result {
  FIRVisionImage *image = [self dataToVisionImage:call.arguments];
  NSDictionary *options = call.arguments[@"options"];

  NSNumber *handle = call.arguments[@"handle"];
  id<Detector> detector = detectors[handle];
  if (!detector) {
    if ([call.method hasPrefix:@"BarcodeDetector"]) {
      detector = [[BarcodeDetector alloc] initWithVision:[FIRVision vision] options:options];
    } else if ([call.method hasPrefix:@"FaceDetector"]) {
      detector = [[FaceDetector alloc] initWithVision:[FIRVision vision] options:options];
    } else if ([call.method hasPrefix:@"ImageLabeler"]) {
      detector = [[ImageLabeler alloc] initWithVision:[FIRVision vision] options:options];
    } else if ([call.method hasPrefix:@"TextRecognizer"]) {
      detector = [[TextRecognizer alloc] initWithVision:[FIRVision vision] options:options];
    }

    [FLTFirebaseMlVisionPlugin addDetector:handle detector:detector];
  }

  [detectors[handle] handleDetection:image result:result];
}

- (FIRVisionImage *)dataToVisionImage:(NSDictionary *)imageData {
  NSString *imageType = imageData[@"type"];

  if ([@"file" isEqualToString:imageType]) {
    return [self filePathToVisionImage:imageData[@"path"]];
  } else if ([@"bytes" isEqualToString:imageType]) {
    return [self bytesToVisionImage:imageData];
  } else {
    NSString *errorReason = [NSString stringWithFormat:@"No image type for: %@", imageType];
    @throw [NSException exceptionWithName:NSInvalidArgumentException
                                   reason:errorReason
                                 userInfo:nil];
  }
}

- (FIRVisionImage *)filePathToVisionImage:(NSString *)filePath {
  UIImage *image = [UIImage imageWithContentsOfFile:filePath];

  if (image.imageOrientation != UIImageOrientationUp) {
    CGImageRef imgRef = image.CGImage;
    CGRect bounds = CGRectMake(0, 0, CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
    UIGraphicsBeginImageContext(bounds.size);
    CGContextDrawImage(UIGraphicsGetCurrentContext(), bounds, imgRef);
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    image = newImage;
  }

  return [[FIRVisionImage alloc] initWithImage:image];
}

- (FIRVisionImage *)bytesToVisionImage:(NSDictionary *)imageData {
  FlutterStandardTypedData *byteData = imageData[@"bytes"];
  NSData *imageBytes = byteData.data;

  NSDictionary *metadata = imageData[@"metadata"];
  NSArray *planeData = metadata[@"planeData"];
  size_t planeCount = planeData.count;

  NSNumber *width = metadata[@"width"];
  NSNumber *height = metadata[@"height"];

  NSNumber *rawFormat = metadata[@"rawFormat"];
  FourCharCode format = FOUR_CHAR_CODE(rawFormat.unsignedIntValue);

  CVPixelBufferRef pxBuffer = NULL;
  if (planeCount == 0) {
    @throw [NSException exceptionWithName:NSInvalidArgumentException
                                   reason:@"Can't create image buffer with 0 planes."
                                 userInfo:nil];
  } else if (planeCount == 1) {
    NSDictionary *plane = planeData[0];
    NSNumber *bytesPerRow = plane[@"bytesPerRow"];

    pxBuffer = [self bytesToPixelBuffer:width.unsignedLongValue
                                 height:height.unsignedLongValue
                                 format:format
                            baseAddress:(void *)imageBytes.bytes
                            bytesPerRow:bytesPerRow.unsignedLongValue];
  } else {
    pxBuffer = [self planarBytesToPixelBuffer:width.unsignedLongValue
                                       height:height.unsignedLongValue
                                       format:format
                                  baseAddress:(void *)imageBytes.bytes
                                     dataSize:imageBytes.length
                                   planeCount:planeCount
                                    planeData:planeData];
  }

  return [self pixelBufferToVisionImage:pxBuffer];
}

- (CVPixelBufferRef)bytesToPixelBuffer:(size_t)width
                                height:(size_t)height
                                format:(FourCharCode)format
                           baseAddress:(void *)baseAddress
                           bytesPerRow:(size_t)bytesPerRow {
  CVPixelBufferRef pxBuffer = NULL;
  CVPixelBufferCreateWithBytes(kCFAllocatorDefault, width, height, format, baseAddress, bytesPerRow,
                               NULL, NULL, NULL, &pxBuffer);
  return pxBuffer;
}

- (CVPixelBufferRef)planarBytesToPixelBuffer:(size_t)width
                                      height:(size_t)height
                                      format:(FourCharCode)format
                                 baseAddress:(void *)baseAddress
                                    dataSize:(size_t)dataSize
                                  planeCount:(size_t)planeCount
                                   planeData:(NSArray *)planeData {
  size_t widths[planeCount];
  size_t heights[planeCount];
  size_t bytesPerRows[planeCount];

  void *baseAddresses[planeCount];
  baseAddresses[0] = baseAddress;

  size_t lastAddressIndex = 0;  // Used to get base address for each plane
  for (int i = 0; i < planeCount; i++) {
    NSDictionary *plane = planeData[i];

    NSNumber *width = plane[@"width"];
    NSNumber *height = plane[@"height"];
    NSNumber *bytesPerRow = plane[@"bytesPerRow"];

    widths[i] = width.unsignedLongValue;
    heights[i] = height.unsignedLongValue;
    bytesPerRows[i] = bytesPerRow.unsignedLongValue;

    if (i > 0) {
      size_t addressIndex = lastAddressIndex + heights[i - 1] * bytesPerRows[i - 1];
      baseAddresses[i] = baseAddress + addressIndex;
      lastAddressIndex = addressIndex;
    }
  }

  CVPixelBufferRef pxBuffer = NULL;
  CVPixelBufferCreateWithPlanarBytes(kCFAllocatorDefault, width, height, format, NULL, dataSize,
                                     planeCount, baseAddresses, widths, heights, bytesPerRows, NULL,
                                     NULL, NULL, &pxBuffer);

  return pxBuffer;
}

- (FIRVisionImage *)pixelBufferToVisionImage:(CVPixelBufferRef)pixelBufferRef {
  CIImage *ciImage = [CIImage imageWithCVPixelBuffer:pixelBufferRef];

  CIContext *temporaryContext = [CIContext contextWithOptions:nil];
  CGImageRef videoImage =
      [temporaryContext createCGImage:ciImage
                             fromRect:CGRectMake(0, 0, CVPixelBufferGetWidth(pixelBufferRef),
                                                 CVPixelBufferGetHeight(pixelBufferRef))];

  UIImage *uiImage = [UIImage imageWithCGImage:videoImage];
  CVPixelBufferRelease(pixelBufferRef);
  CGImageRelease(videoImage);
  return [[FIRVisionImage alloc] initWithImage:uiImage];
}

+ (void)addDetector:(NSNumber *)handle detector:(id<Detector>)detector {
  if (detectors[handle]) {
    NSString *reason =
        [[NSString alloc] initWithFormat:@"Object for handle already exists: %d", handle.intValue];
    @throw [[NSException alloc] initWithName:NSInvalidArgumentException reason:reason userInfo:nil];
  }

  detectors[handle] = detector;
}
@end