Snapshot of an App

There are four ways to take a picture of the screen of your app.

1. Press the Sleep and Home buttons simultaneously.

If your app is running on an iPhone, simultaneously press the Sleep/wake button (upper right on iPhone and iPad, upper left on iPod Touch) and the Home button. This will save a 320 × 480 photo of the screen, including the status bar, in the iPhone’s Photos. You can then mail it to yourself. Oddly, the photo is in jpg format even though Apple recommends png format for images displayed by an app.

2. Take the photo in Xcode.

If your app is running on an iPhone connected to Xcode,
Window → Organizer → Devices → iPhone
Screenshot
Capture
Then drag the big captured image on the left (a 320 × 480 png, including status bar) onto the desktop of your Mac.

You can use the resulting image as the app’s launch image. Rename it Default.png, move it to the app’s folder, and add it to the project.

Project → Add to Project…
Add
Add

3. Have the app take its own picture.

If the app is running on the Simulator, it can take its own picture. Paste the following import above the others at the top of the HelloWorldAppDelegate.m file. It is needed for the call to renderInContext:.

#import <QuartzCore/QuartzCore.h>

Paste the following code into the application:didFinishLaunchingWithOptions: method of the application delegate immediately after the call to the makeKeyAndVisible method of the window.

	UIGraphicsBeginImageContext(window.bounds.size);
		[window.layer renderInContext: UIGraphicsGetCurrentContext()];
		UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
	UIGraphicsEndImageContext();

	if (image == nil) {
		NSLog(@"UIGraphicsGetImageFromCurrentImageContext failed");
		return YES;
	}

	NSData *d = UIImagePNGRepresentation(image);
	if (d == nil) {
		NSLog(@"UIImagePNGRepresentation failed");
		return YES;
	}

	NSString *fileName = [NSString stringWithFormat:
		@"%@/snapshot.png", NSHomeDirectory()];

	if (![d writeToFile: fileName atomically: NO]) {
		NSLog(@"writeToFile:atomically: failed");
		return YES;
	}

Then run the app in the simulator. To find the resulting snapshot.png file on your Mac, launch Terminal.app and say

find / -type f -name snapshot.png 2> /dev/null

/Users/nyuuser/Library/Application Support/iPhone Simulator/4.1/Applications/242571E9-DDDF-4892-84FB-B87486AB909F/snapshot.png

On an iPhone, the image is 320 × 480 pixels, with the top 20 rows occupied by the status bar.

1. Sleep and Home buttons (jpg)	2. Xcode Organizer screenshot (png)	3. GetImageFromCurrentImageContext (png)

4. Take a picture of the simulator

If the Simulator is simulating an iPhone 4 at scale == 100% or an iPad at scale == 100%, select
Window → Zoom
and zoom it to the largest size. If the largest size still has scrollbars, scroll to the upper left corner of the picture. Click on the Simulator and press Command-Shift-4. The cursor will turn into a crosshair with x and y coördinates. Press the space bar to turn the cursor into a camera and to whiten the Simulator. Click on the Simulator and you will hear the sound of the shutter. An image of the simulator will be saved on the Desktop in a PNG file whose name is in the format Screen shot 2011-12-31 at 11.59.59 AM.png. The title bar adds an extra 22 pixels to the top of an iPhone 4 or iPad image. The files you get will be smaller if the screen of your Mac isn’t big enough to display the entire simulator.

Grab

You can also photogaph the Simulator with the Mac application Grab.app. Go to the finder,
File → Find…
Grab.app
Launch Grab.app.

Capture → Window
When the window you want is ready, click Choose
Window, then click the window to capture it.

File → Save As…

You can convert the resulting 386 × 742 TIFF file to PNG with Preview.