How to pop up the UIImagePickerController in an iphone to select an image?

There are several ways to let the user select an image from a iphone or an ipad. All what we have to do is to use the UIImagePickerController to start the image picking task from the Photo Library, Saved Photos Album and the Camera.
In this post I'm going to explain how to pick an image from the Photo Library. So, make sure that you have images in your photo Library.

Note that you have to tell the program header file (your .h file) that you are using the following delegates

UIApplicationDelegate
UIImagePickerControllerDelegate
UINavigationControllerDelegate

All what you have to do is adding a button on your screen and let the user click on it to start popping up the image picker, let them select an image. If an image is selected successfully, then automatically the delegate method didFinishPickingMediaWithInfo will be called where you can view your image in a UIImageView or do whatever the processing you want with the image.

-(IBAction)selectImage:(id)sender
{
     [self selectAnImage];
}

//method to let the user select an image from the UIImagePickerView
-(void)selectAnImage
{
    ipc=[[UIImagePickerController alloc] init];//instantiate a UIImagePickerViewController object
    ipc.delegate=self;

    //First I am checking that the camera is available
    if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera])
    {
        NSLog(@"Camera is available");
        ipc.sourceType=UIImagePickerControllerSourceTypeCamera; 
    }
    
    //if not check whether the saved photo album is available
    else if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeSavedPhotosAlbum])
    {
        NSLog(@"Camera is not available");
        NSLog(@"Photo Album is available");
        
        ipc.sourceType=UIImagePickerControllerSourceTypeSavedPhotosAlbum;  
    }
    
    //if none of the above two are avaialble, then use the Photo Library
    else
    {
        NSLog(@"Camera is not available");
        NSLog(@"Photo Album is not available");
        NSLog(@"Photo Library is available");
        
        ipc.sourceType=UIImagePickerControllerSourceTypePhotoLibrary;
    }
    
     [self presentModalViewController:ipc animated:YES];
}

//ImagePickerControler delegate
//triggers when the user has selected an image
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    
    NSArray *paths = NSSearchPathForDirectoriesInDomains( NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *filePath = [[paths objectAtIndex:0]stringByAppendingPathComponent:@"Test.txt"];
    NSString *temp=[[NSString alloc]initWithString:@"Sample String"];
    [temp writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:nil];
      
    //set the selected image
    self.sourceImage=[info objectForKey:UIImagePickerControllerOriginalImage];
    imageDisplay.image=self.sourceImage;    
    [self checkImageResolution:self.sourceImage];
    [[picker parentViewController]dismissModalViewControllerAnimated:YES];
    [picker dismissModalViewControllerAnimated:YES];
}

//ImagePickerControler delegate
//triggers when user did cancel the image selection from the UIimagePickerView
- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
{
  [[picker parentViewController]dismissModalViewControllerAnimated:YES];
}

Working with images and the camera in ios

If we are wanting to work with the images and the camera there are some approaches available for us in iphone. We have to let the user select a bunch of images in any of this scenarios

• Camera may or may not be available but the photo library is
• Video may or may not be available
• We can use the provided picker control without trying to reinvent the wheel because the picker supports different sources  (e.g:- Photo Library , Saved Photos or Camera)
• Always check to see if your desired source is available ( even tough you want the camera to provide images for you, you still let the user know the nonavailability of the camera and provide another solution to get images.

How to use the image picker?

In order to use the Image Picker, we need to,

• Create an instance of the UIImagePickerController and set yourself as the delegate for it
• When needed, choose your source type (photo Library, Saved Photos or Camera) and animate the Picker
• Respond to the delegate events for the user either picking an image or cancelling.

Now, my task is to let my app access the photo library in the Simulator, let the user select an image and finally let the image to view in my app.

One of the prerequisite for this app is 'we need to have images in the photo library to let the user select one'. just run your simulator and click on the Photos option (Sunflower icon) to check whether there are images. If not, it will look like below,

but it's very simple to add images to the photo library. have one or more images in your desktop, drag and drop an image i to the simulator, click and hold the image for a second, when three buttons prompts asking for the task to do , click on Save Image to add the image to the photo library. you can add few more images like this. 

Now if you come back and go to the photo library once again, you can save that the added images are there in it.

Now, let's go ahead and make a simple application that uses the image picker. 

Create a View based application, add a UIImageView to the entire screen and add a button on top of it. That's all with the design.

Now, you have to start coding with it. keep in mind the steps I showed you on how to work with Image Picker controller.

examine the code in the header file below.

//  ImagePickerViewControllerViewController.h

#import <UIKit/UIKit.h>

@interface ImagePickerViewControllerViewController : UIViewController 

//you must add this to indicate that we are going to use the delegates of UIPickerController and //UINavigationController

<UIImagePickerControllerDelegate,UINavigationControllerDelegate>   

{

    UIImagePickerController *ipc;

    IBOutlet UIImageView *bgImage;

}

@property (nonatomic,retain) UIImageView *bgImage;

-(IBAction) buttonClicked;

@end

Now, examine the implantation of it as below.

//  ImagePickerViewControllerViewController.m

#import "ImagePickerViewControllerViewController.h"

@implementation ImagePickerViewControllerViewController

@synthesize bgImage;

- (void)dealloc

{

    [super dealloc];

}

- (void)didReceiveMemoryWarning

{

    [super didReceiveMemoryWarning];

}

#pragma mark - View lifecycle

- (void)viewDidUnload

{

    [super viewDidUnload];

}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation

{

    return (interfaceOrientation == UIInterfaceOrientationPortrait);

}

//this function will be triggered when the button is clicked

-(IBAction) buttonClicked

{

    ipc=[[UIImagePickerController alloc] init];   //we instantiate a UIImagePickerController object

    ipc.delegate=self;                                         //we are going to take the control of it

    

//if the camera is available, let it be the source of the image picker object

    if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera])

    {

        ipc.sourceType=UIImagePickerControllerSourceTypeCamera;             

    }

    

//if the camera is not available

    else

    {

        //display an alert (message box) saying so

        UIAlertView *alert=[[UIAlertView  alloc] initWithTitle:@"Information" message:@"Camera Unavailable" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];

        

        [alert show];

        [alert release];

//then let the source be the Photo Library

        ipc.sourceType=UIImagePickerControllerSourceTypePhotoLibrary;

    }

    

    [self presentModalViewController:ipc animated:YES];

}

//-------------------------the delegate methods of the UIImagePicker controller

//this method talks to the parent control and dismiss the model view controller and release it

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker

{

    [[picker parentViewController]dismissModalViewControllerAnimated:YES];

    [picker release];

}

//we are going to set the image to the background image on our app

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info

{

    //set image

    bgImage.image=[info objectForKey:UIImagePickerControllerOriginalImage];

    

    //release picker

    [[picker parentViewController]dismissModalViewControllerAnimated:YES];

    [picker release];}

@end

Following are some of the screen shots of running program.

Now you can build and run your app. I also have made available the project source code for you. 

Click to Download