ios添加图片为什么从相册里面就可以，从摄像头上就不行，小白求解答

- (void) openCamera { 
     NSLog(@"********** open camera"); 

    AVCaptureSession *session = [[[AVCaptureSession alloc] init] autorelease];      

    session.sessionPreset = AVCaptureSessionPreset640x480;
    
     AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; 
     
     NSError *error = nil; 
     // 创建数据输入来源 
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error]; 
     if (input) { 
         // 添加接口 
        [session addInput:input]; 
         
         stillImageOutput = [[[AVCaptureStillImageOutput alloc] init] autorelease]; 
         NSDictionary *outputSettings = [[[NSDictionary alloc] initWithObjectsAndKeys:AVVideoCodecJPEG,AVVideoCodecKey,nil] autorelease]; 
         [stillImageOutput setOutputSettings:outputSettings]; 
         [session addOutput:stillImageOutput]; 
         
         //宣告一個AVCaptureVideoPreviewLayer的指標，用來存放session要輸出的東西（Camera中的畫面） 
        AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session]; 
         
         //設定輸出畫面的邊界大小 
        previewLayer.frame = CGRectMake(0, 54, 320, 372); 
         
         //將輸出的東西透過preview秀出來，preview為UIImageView型態 
        [self.view.layer addSublayer:previewLayer]; 
         
         //完成session的輸入端與輸出端的相關設定之後，啟動的這個session，它將會自動將輸入端與輸出端做連結 
        [session startRunning]; 
     }else { 
         NSLog(@"********** camera got Error:"); 
     } 

}

// 拍照

- (IBAction) shot:(id)sender {
     NSLog(@"********** take a shot");
     
     AVCaptureConnection *videoConnection = nil;
     for (AVCaptureConnection *connection in stillImageOutput.connections) {
         for (AVCaptureInputPort *port in [connection inputPorts]) {
             if ([[port mediaType] isEqual:AVMediaTypeVideo]) {
                 videoConnection = connection;
                 break;
             }
         }
         if (videoConnection) {
             break;
         }
     }
     
     // NSLog(@"about to request a capture from:%@",stillImageOutput);
     // block方法 & 记得 #import <ImageIO/ImageIO.h>
     [stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:
      ^(CMSampleBufferRef imageSampleBuff, NSError *error){
          CFDictionaryRef exifAttachments = CMGetAttachment(imageSampleBuff, kCGImagePropertyPNGDictionary, NULL);
          if (exifAttachments) {
              // NSLog(@"attachments :%@",exifAttachments);
              
          }else {
              NSLog(@"no attachments");
          }
          NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuff];
          
          UIImage *image = [UIImage imageWithData:imageData];
          
          NSLog(@"----%f, %f",image.size.width, image.size.height);
          
      }
      ];
     
 }

http://jingyan.baidu.com/article/e73e26c0bcb06824adb6a785.htmlios
从摄像头/相册获取图片