Capture still image be stretched with Cocoa Touch AVFoundation framework - iphone

Question

I must capture still image with cocoa touch AVFoundation framework,but I found that captured image be stretched.
I have configured the captureSession as these:
[self setPreviewLayer:[[AVCaptureVideoPreviewLayer alloc] initWithSession:[self captureSession]]];
self.captureSession.sessionPreset=AVCaptureSessionPresetHigh;
[[self previewLayer] setVideoGravity:AVLayerVideoGravityResizeAspectFill];
And use these code to capture image:
[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error)
{
if(error)
NSLog(#"error=%#",error);
else
{
if (imageDataSampleBuffer != NULL) {
NSData *imageData=[AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage *image=[[UIImage alloc] initWithData:imageData];
CGRect screenRect = [[UIScreen mainScreen] bounds];
CGFloat screenWidth = screenRect.size.width;
CGFloat screenHeight = screenRect.size.height;
CGSize screenSize=CGSizeMake(screenWidth, screenHeight);
NSLog(#"screen.width=%f,screen.height=%f",screenWidth,screenHeight);
UIGraphicsBeginImageContextWithOptions(screenSize, NO, 0.0f);
// This is where we resize captured image
[(UIImage *)image drawInRect:CGRectMake(0, 0, screenWidth, screenHeight)];
CGSize imageSize=[ImageUtility getImageSize:image];
NSLog(#"image.width=%f,image.height=%f",imageSize.width,imageSize.height);
// Save the results directly to the image view property
UIImage *toSaveImage=UIGraphicsGetImageFromCurrentImageContext();
imageSize=[ImageUtility getImageSize:toSaveImage];
NSLog(#"combine.width=%f,combine.height=%f",imageSize.width,imageSize.height);
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(toSaveImage, nil, nil, nil);
}
}
}];
}
This result output:
013-08-29 09:30:06.182 WatermarkCamera[6882:907] screen.width=320.000000,screen.height=480.000000
2013-08-29 09:30:07.208 WatermarkCamera[6882:907] image.width=1280.000000,image.height=720.000000
2013-08-29 09:30:07.238 WatermarkCamera[6882:907] combine.width=640.000000,combine.height=960.000000
The result output image stretched.How to fix the stretched image?Any suggestions should be appreciated.

Answer 1

I think I shouldn't draw image with the size of screen.I should draw image with the size of image.
I have defined new method to scale image to new width
+(UIImage*)imageWithImage: (UIImage*) sourceImage scaledToWidth: (float) i_width;
Now I called this method
UIImage *newImage=[ImageUtility imageWithImage:image scaledToWidth:screenWidth];
[newImage drawInRect:CGRectMake(0, 0, newImage.size.width, newImage.size.height)];
Finally write the new image to photo album.The new image doesn't stretch.