Since the release of the iPhone 4 I’ve been meaning to take a few minutes and write a flashlight application using the LED. My understanding from what I’ve gleaned from the API’s is that in order to turn on the LED, we need to essentially go through the same steps we would to capture video – if you know of a quicker and/or simpler process, please post some code below.

iPhone Flashlight UI

The user interface of this app is about as simple as they get – nothing more than a button to toggle the flashlight on and off.

The code for the UI is equally as trivial, in loadView, check if the device has a torch and if so, add a button to toggle the flashlight state.

- (void)loadView
{
  [self setView:[[[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]] autorelease]];
 
  AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
 
  // If torch supported, add button to toggle flashlight on/off
  if ([device hasTorch] == YES)
  {
    flashlightButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 120, 320, 98)];
    [flashlightButton setBackgroundImage:[UIImage imageNamed:@"TorchOn.png"] forState:UIControlStateNormal];
     [flashlightButton addTarget:self action:@selector(buttonPressed:) forControlEvents: UIControlEventTouchUpInside];      
 
    [[self view] addSubview:flashlightButton];
  }
}

Toggling the Flashlight On and Off

The event management code for this app is nothing more than swapping the button background image to reflect the current state of the flashlight followed by a call to the code that will toggle the LED on and off.

- (void)buttonPressed:(UIButton *)button
{
  if (button == flashlightButton)
  {
    if (flashlightOn == NO)
    {
      flashlightOn = YES;
      [flashlightButton setBackgroundImage:[UIImage imageNamed:@"TorchOff.png"] forState:UIControlStateNormal];
    }
    else
    {
      flashlightOn = NO;
      [flashlightButton setBackgroundImage:[UIImage imageNamed:@"TorchOn.png"] forState:UIControlStateNormal];
    }
 
    [self toggleFlashlight];
  }
}

AVCaptureSession Configuration

There are a few objects that we’ll need to interact with to get everything working. AVCaptureDevice is the object we’ll use to represent the physical video device. An AVCaptureSession object will manage the flow of data. And finally, AVCaptureDeviceInput will represent the video data.

With the objects above defined, we configure the AV session to set the torch on and start the session running…

- (void)toggleFlashlight
{
  AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
 
  if (device.torchMode == AVCaptureTorchModeOff)
  {
    // Create an AV session
    AVCaptureSession *session = [[AVCaptureSession alloc] init];
 
    // Create device input and add to current session
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error: nil];
    [session addInput:input];
 
    // Create video output and add to current session
    AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
    [session addOutput:output];
 
    // Start session configuration
    [session beginConfiguration];
    [device lockForConfiguration:nil];
 
    // Set torch to on
    [device setTorchMode:AVCaptureTorchModeOn];
 
    [device unlockForConfiguration];
    [session commitConfiguration];
 
    // Start the session
    [session startRunning];
 
    // Keep the session around
    [self setAVSession:session];
 
    [output release];
  }
  else
  {
    [AVSession stopRunning];
    [AVSession release], AVSession = nil;
  }
}

Caveats

Stating the obvious, this application will only work on iPhone 4+ devices. Also, this application works on only on a device – you will receive compile time errors regarding AVCaptureSession if you attempt to build the app for the simulator.

One last thought – chances are running the LED for any length of time may give your battery a pretty intense workout. It may be worthwhile to keep an eye on your battery indicator if you plan to turn the light on for more than a few minutes.

iPhone LED Flashlight- Xcode Project

Here is the link to download the source code for the iPhone LED Flashlight application.

It’s surprising easy to create a bare bones camera application on the iPhone. UIImagePickerController provides a means to access the camera, take a photo and preview the results. There is also an option to allow resizing and scaling of a photo once captured. Using UIImageWriteToSavedPhotosAlbum in the UIKit, you can easily save an image to the Photo Album.

The image on the left in the figure below shows the camera active in the application. The image on the right is the preview option once a photo has been taken.

Start the Camera

To work with the camera we begin by creating a UIImagePickerController object and setting the sourceType to UIImagePickerControllerSourceTypeCamera. For this example, I set allowsImageEditing to NO to disable editing of photos image. I use presentModalViewController to initiate the display of the camera.

// Create image picker controller
UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
 
// Set source to the camera
imagePicker.sourceType =  UIImagePickerControllerSourceTypeCamera;
 
// Delegate is self
imagePicker.delegate = self;
 
// Allow editing of image ?
imagePicker.allowsImageEditing = NO;
 
// Show image picker
[self presentModalViewController:imagePicker animated:YES];

Save Image to Photo Album

Once a photo has been taken, the method didFinishPickingMediaWithInfo will be called, providing the opportunity to write the image to the Photo Album:

- (void) imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
  // Access the uncropped image from info dictionary
  UIImage *image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
 
  // Save image
  UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
 
  [picker release];
}

Notice the call selector reference above, this selector will be called once the image has been written to the system. For this example I display an alert showing the result of attempting to save the image:

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
  UIAlertView *alert;
 
  // Unable to save the image  
  if (error)
    alert = [[UIAlertView alloc] initWithTitle:@"Error" 
                            message:@"Unable to save image to Photo Album." 
                            delegate:self cancelButtonTitle:@"Ok" 
                            otherButtonTitles:nil];
  else // All is well
    alert = [[UIAlertView alloc] initWithTitle:@"Success" 
                            message:@"Image saved to Photo Album." 
                            delegate:self cancelButtonTitle:@"Ok" 
                            otherButtonTitles:nil];
  [alert show];
  [alert release];
}

Optional Updates

This is a good, if not simple, place to start. Here are two additional updates to this application you can tinker with:

#1 – Check for a camera on device. Refer to this post Does iPhone Support Camera to learn more.

#2 – Set the image editing option to YES. This will require a few additional changes including a request to the information dictionary to return the cropping rectangle that was applied to the original image (see UIImagePickerControllerCropRect).

Source Code

You can download the source code for the camera application here.

Simulator Not Supported

One last note, this application will only run on an actual device as the simulator does not have camera support.

This tip is from Chapter 9 – Camera, Mapkit and Core Location and shows how to make a quick check on the status/availability of the camera on device.

Book Giveaway

We are no longer accepting entries for today’s giveaway.

Is the Camera Available and Ready?

Not all devices support the same source media capabilities, for example, there is no currently no camera on the iPod touch. In addition, even if a device does support a specific media source, that source could be busy – for example, the camera on an iPhone may be in use.

This short snippet of code demonstrates how to check if a device has a camera and/or if the camera is available:

if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera] == YES)
  NSLog(@"Camera is available and ready");
else
  NSLog(@"Camera is not available");

Note that when using the Simulator within Xcode, this call will return NO, as there is no camera available.

Does iPhone Support Recording Video?

The only iPhone to support video recording is the 3GS. There are two checks required before you can use the technology in your application. First, check to see if a camera is available, and second, verify the media types available on the device includes movies.

if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera] == YES)
  NSLog(@"Camera is available and ready");
else
  NSLog(@"Camera is not available");
 
NSArray *media = [UIImagePickerController
     availableMediaTypesForSourceType: UIImagePickerControllerSourceTypeCamera];
 
if ([media containsObject:@"public.movie"] == YES)
  NSLog(@"Video recording available");
else 
  NSLog(@"Video recording is not available");

Let’s begin with the method description to save an image:

  void UIImageWriteToSavedPhotosAlbum(UIImage *image, 
                  id completionTarget, SEL completionSelector, void *contextInfo);

completionTarget refers to the object in which the completionSelector can be found. In other words, what object has the method that will be called once the file write is complete? contextInfo is a void * that you can use to specify content to be passed to the completionSelector.

Obviously, the image is a required paramater. The other three are only needed if you prefer to be notified asynchronously when the write is complete. Here’s how a call to the above method might look:

  // Image to save
  UIImage *img = [UIImage imageNamed:@"ImageName.png"];  
 
  // Request to save the image to camera roll
  UIImageWriteToSavedPhotosAlbum(img, self, 
              @selector(image:didFinishSavingWithError:contextInfo:), nil);

Here we are specifying that the selector to be called upon completion is within this object (self). A template for this selector could look as follows:

  - (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error 
             contextInfo:(void *)contextInfo
  {
    // Was there an error?
    if (error != NULL)
    {
      // Show error message...
 
    }
    else  // No errors
    {
      // Show message image successfully saved
    }
  }

Add code for displaying the appropriate message based on success or failure of the image save, and you’re good to go.

For the most part, capturing images of your application is as simple as running the simulator and pressing Shift-Command-4. However, when working with the simulator there are times when you cannot get to the screen contents you want to capture or otherwise are constrained by the simulator.

For instance, an application I was working on recently involved taking a picture with the camera. Once the photo was taken, the user was to provide some additional information about the photo. Because the next steps were non-trivial, we decided a help screen was in order. To create this screen, I wanted a screenshot of a photo taken by the application, which I would then markup using an image editing program to write notes as to what the user needed to do next.

Problem is, there are limitations of the camera when working with the simulator. The end result was, when running in the simulator the screen I needed to explain could not be shown with an actual photograph taken from the application (it would always be a black screen).

The work around that I came up with was to run the application on a real device, get to the screen I wanted to capture, create a screenshot, email myself the image, then edit as needed and incorporate into the application as a help screen.

The steps for capturing a screenshot on an iPhone are to navigate to the screen you want to capture, then:

Step #1 – Press and hold the Home control
Step #2 – Press the Sleep control

The captured image will be stored in the Camera Roll.