ios - 通过蓝牙 4.0 LE 发送图像文件

Question

我正在尝试通过蓝牙 4.0 LE 将 .png 图像文件从一台 iOS 设备发送到另一台。

我能够处理像字符串这样的简单数据，但无法成功发送和使用图像文件。

在外围设备中，我从这个开始

pictureBeforeData = [UIImage imageNamed:@"myImage.png"];
NSData *myData = UIImagePNGRepresentation(pictureBeforeData);

然后我将 myData 设为特征值。

_myCharacteristic =
[[CBMutableCharacteristic alloc] initWithType:_myCharacteristicUUID
                                   properties:CBCharacteristicPropertyRead
                                        value:myData
                                  permissions:CBAttributePermissionsReadable];

在中央设备中，当特征值更新时我有这个

- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error {
  if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:_myCharacteristicUUID]]) {
    NSLog(@"PICTURE CHARACTERISTIC FOUND"); // This successfully gets logged

    NSData *dataFromCharacteristic = [[NSData alloc] initWithData:characteristic.value];

    UIImage *imageFromData = [[UIImage alloc]initWithData:dataFromCharacteristic];

    // This correctly logs the size of my image
    NSLog(@"SIZE: %f, %f", imageFromData.size.height, imageFromData.size.width);

    // This causes the imageView to turn completely black
    _sentPictureImageView.image = imageFromData;

    if (!([_myImagesArray containsObject:imageFromData]))
    {
      NSLog(@"DOES NOT CONTAIN"); // This is successfully logged
      [_myImagesArray addObject:imageFromData]; // This runs but is apparently not adding the image to the array
    }

    NSLog(@"COUNT: %u", _contactsImagesArray.count); // This always logs 0 - The array is empty }

编辑 8-27-13: 我能够成功发送一个单一颜色的 1by1 像素 .png 文件，该文件大约有 5,600 字节大。我无法发送只有大约 2,000 字节的多色 20by20pixel .png 文件。我能够发送仅包含一种颜色和较少像素的较大文件，但无法发送包含多种颜色和较多像素的较小文件。

编辑 8-30-13: 我必须将数据解析成更小的 block 。在 Apple 的一个示例项目中，我发现了一种方法可以做到这一点。我似乎无法确切地理解如何在我自己的代码中实现它，但我目前正在尝试弄清楚如何实现。这是代码:

- (void)sendData {
// First up, check if we're meant to be sending an EOM
static BOOL sendingEOM = NO;

if (sendingEOM) {

    // send it
    BOOL didSend = [self.peripheralManager updateValue:[@"EOM" dataUsingEncoding:NSUTF8StringEncoding] forCharacteristic:self.transferCharacteristic onSubscribedCentrals:nil];

    // Did it send?
    if (didSend) {

        // It did, so mark it as sent
        sendingEOM = NO;

        NSLog(@"Sent: EOM");
    }

    // It didn't send, so we'll exit and wait for peripheralManagerIsReadyToUpdateSubscribers to call sendData again
    return;
}

// We're not sending an EOM, so we're sending data

// Is there any left to send?

if (self.sendDataIndex >= self.dataToSend.length) {

    // No data left.  Do nothing
    return;
}

// There's data left, so send until the callback fails, or we're done.

BOOL didSend = YES;

while (didSend) {

    // Make the next chunk

    // Work out how big it should be
    NSInteger amountToSend = self.dataToSend.length - self.sendDataIndex;

    // Can't be longer than 20 bytes
    if (amountToSend > NOTIFY_MTU) amountToSend = NOTIFY_MTU;

    // Copy out the data we want
    NSData *chunk = [NSData dataWithBytes:self.dataToSend.bytes+self.sendDataIndex length:amountToSend];

    // Send it
    didSend = [self.peripheralManager updateValue:chunk forCharacteristic:self.transferCharacteristic onSubscribedCentrals:nil];

    // If it didn't work, drop out and wait for the callback
    if (!didSend) {
        return;
    }

    NSString *stringFromData = [[NSString alloc] initWithData:chunk encoding:NSUTF8StringEncoding];
    NSLog(@"Sent: %@", stringFromData);

    // It did send, so update our index
    self.sendDataIndex += amountToSend;

    // Was it the last one?
    if (self.sendDataIndex >= self.dataToSend.length) {

        // It was - send an EOM

        // Set this so if the send fails, we'll send it next time
        sendingEOM = YES;

        // Send it
        BOOL eomSent = [self.peripheralManager updateValue:[@"EOM" dataUsingEncoding:NSUTF8StringEncoding] forCharacteristic:self.transferCharacteristic onSubscribedCentrals:nil];

        if (eomSent) {
            // It sent, we're all done
            sendingEOM = NO;

            NSLog(@"Sent: EOM");
        }

        return;
    }
}}

我的imageView是黑色方 block ，应该是显示我发过来的图片。

Answer 1

在 iOS 6 上，BLE 允许您发送大约 20 字节的数据 block 。有关如何分割要发送的数据以及如何使用基于通知的传输的示例，请下载 BTLE Transfer Apple Example application .

为了更好地了解您可以达到的速度，我建议您分析这张图 http://www.scriptreactor.com/conn_interval-throughput.pdf它显示了作为连接间隔函数的可实现速度。 iOS 不会为您提供如此细粒度的控制，但此信息对于您进行计算仍然很有值(value)。