iOS screen capture & UIImagePickerController 快速擷取螢幕&取得相片圖檔

一般來說在iOS系列產品只要同時按下Home+Power即可把螢幕快速擷取，擷取下來的圖片就會存在"相片"中(語言設定為英文即顯示"Photos")，是個相當好用的功能，但在程式中該如何快速擷取呢？以下就來講解一下

Download Example

首先來講擷取部份，先在.h檔內import
#import <QuartzCore/QuartzCore.h>

再來到.m檔內設定一個按鈕來做擷取的動作，在此直接在viewDidLoad直接建立按鈕，當然也可以用IB等其他方式來做
UIButton *myButton = [[UIButton alloc] initWithFrame:CGRectMake(10, 410, 140, 40)];
[myButton setBackgroundColor:[UIColor blackColor]];
[myButton setTitle:@"screen capture" forState:UIControlStateNormal];
[myButton addTarget:self action:@selector(capture) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:myButton];
[myButton release];


接著把"capture"這個function也建立出來
-(IBAction) capture{
UIGraphicsBeginImageContext(self.view.bounds.size);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);
//NSLog(@"viewImage = %@",viewImage);
}


到這可以build看看是否可以順利Run，按下按鈕會自動把畫面儲存至"相片"內，重點來了，可是這樣很麻煩，還要關掉app跑去"相片"看，為了懶總是要把這問題解決

目前作法是，畫面中一張圖兩個按鈕，一個按鈕擷取螢幕，另一個連結至"相片"，並且相片選取後可以丟到畫面中的圖片位置，先把剛剛的.h檔改為
#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>

@interface screenCaptureViewController : UIViewController {
UIImagePickerController *imagePicker;
UIImageView *imageView;
}

@property (nonatomic, retain) UIImagePickerController *imagePicker;

@end


再來到.m檔部份，首先在@implementation與@end中間加入這行，將UIImagePickerController用property來管理記憶體
@synthesize imagePicker;


接著在viewDidLoad內加入
//set image
imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 400)];
[imageView setBackgroundColor:[UIColor blackColor]];
[self.view addSubview:imageView];

//set screen capture button
UIButton *myButton = [[UIButton alloc] initWithFrame:CGRectMake(10, 410, 140, 40)];
[myButton setBackgroundColor:[UIColor blackColor]];
[myButton setTitle:@"screen capture" forState:UIControlStateNormal];
[myButton addTarget:self action:@selector(capture) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:myButton];
[myButton release];

//set choose photo button
UIButton *myButton2 = [[UIButton alloc] initWithFrame:CGRectMake(170, 410, 140, 40)];
[myButton2 setBackgroundColor:[UIColor blackColor]];
[myButton2 setTitle:@"choose photo" forState:UIControlStateNormal];
[myButton2 addTarget:self action:@selector(gallery) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:myButton2];
[myButton2 release];

//set image picker
imagePicker = [[UIImagePickerController alloc] init];
imagePicker.delegate = self;
imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;


[self.view setBackgroundColor:[UIColor whiteColor]];


然後在@implementation與@end中間加入這兩個function&delegate
-(IBAction) capture{
UIGraphicsBeginImageContext(self.view.bounds.size);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);
//NSLog(@"viewImage = %@",viewImage);
}

-(IBAction) gallery{
[self presentModalViewController:self.imagePicker animated:YES];
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)img editingInfo:(NSDictionary *)editInfo {
imageView.image = img;
[[picker parentViewController] dismissModalViewControllerAnimated:YES];
}


最後請記得在dealloc把imageView給釋放掉
- (void)dealloc {
[imageView release];
[super dealloc];
}


完成後build起來畫面應該是如下，可以按下screen capture來擷取畫面...不過我懶得寫個alert來提示


點下choose photo


點入相簿內


選取所擷取的畫面就會切回來並且把上面黑色那塊換掉


多用幾次就會變成這樣



Download Example

相關連結
iOS Developer Library
iOS Developer Library - UIImagePickerController Class Reference