一个同事开发iphone拍照后为图片添加滤镜的功能。 发现添加滤镜时总出现方向自动变化的问题。

分析原因：

1 方向没有搞正确。

2 给滤镜方法时图片没有正过来。

1 方向没有搞正确。

解决方法：

因为UIImage本身就自带的imageOrientation的 值， 一般情况下调用相机拍照会自动为照片添加imageOrientation. 但我们使用的是自定义相机功能，所以在拍照时需要为先设定方向值。 而获取方向使用到了通知， 在锁屏的情况下， 方向通知就无法获取了。见如下代码。  google无数页面后， 可以在锁屏方式仍可获取方向的方法。 见如下：

// 通过通知获取方向：（在锁屏方式下无法获取方向）

[notificationCenter addObserver:self selector:@selector(deviceOrientationDidChange) name:UIDeviceOrientationDidChangeNotification object:nil];

- (void)deviceOrientationDidChange

{

UIDeviceOrientation deviceOrientation = [[UIDevice currentDevice] orientation];

if (deviceOrientation == UIDeviceOrientationPortrait)

orientation = AVCaptureVideoOrientationPortrait;

elseif (deviceOrientation == UIDeviceOrientationPortraitUpsideDown)

orientation = AVCaptureVideoOrientationPortraitUpsideDown;

// AVCapture and UIDevice have opposite meanings for landscape left and right (AVCapture orientation is the same as UIInterfaceOrientation)

elseif (deviceOrientation == UIDeviceOrientationLandscapeLeft)

orientation = AVCaptureVideoOrientationLandscapeRight;

elseif (deviceOrientation == UIDeviceOrientationLandscapeRight)

orientation = AVCaptureVideoOrientationLandscapeLeft;

// Ignore device orientations for which there is no corresponding still image orientation (e.g. UIDeviceOrientationFaceUp)

}

// 通过加速器获取方向

参考了老外的博客： http://blog.sallarp.com/iphone-accelerometer-device-orientation/

1》

[[UIAccelerometersharedAccelerometer] setDelegate:self];

2》

@interface AVCamCaptureManager : NSObject<UIAccelerometerDelegate>{

UIInterfaceOrientation deviceOrientation;

}

@property (nonatomic) UIInterfaceOrientation deviceOrientation;

3》

#pragma mark -- 方向

- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration

{

// Get the current device angle

float xx = -[acceleration x];

float yy = [acceleration y];

float angle = atan2(yy, xx);

// Read my blog for more details on the angles. It should be obvious that you

// could fire a custom shouldAutorotateToInterfaceOrientation-event here.

if(angle >= -2.25 && angle <= -0.25)

{

if(deviceOrientation != UIInterfaceOrientationPortrait)

{

deviceOrientation = UIInterfaceOrientationPortrait;

}

}

else if(angle >= -1.75 && angle <= 0.75)

{

if(deviceOrientation != UIInterfaceOrientationLandscapeRight)

{

deviceOrientation = UIInterfaceOrientationLandscapeRight;

}

}

else if(angle >= 0.75 && angle <= 2.25)

{

if(deviceOrientation != UIInterfaceOrientationPortraitUpsideDown)

{

deviceOrientation = UIInterfaceOrientationPortraitUpsideDown;

}

}

else if(angle <= -2.25 || angle >= 2.25)

{

if(deviceOrientation != UIInterfaceOrientationLandscapeLeft)

{

deviceOrientation = UIInterfaceOrientationLandscapeLeft;

}

}

orientation = deviceOrientation;

}

// 自定义拍照方式设置方向：

[stillImageConnection setVideoOrientation:deviceOrientation];

代码如下：

- (void) captureStillImage

{

AVCaptureConnection *stillImageConnection = [AVCamUtilitiesconnectionWithMediaType:AVMediaTypeVideofromConnections:[[selfstillImageOutput] connections]];

if ([stillImageConnection isVideoOrientationSupported])

{

NSLog(@"device orientation: %d", deviceOrientation);

[stillImageConnection setVideoOrientation:deviceOrientation];

}

2 给滤镜方法时图片没有正过来。

生成后的图片会自带一个imageOrientation的值， 默认情况下UIImageView会自动判断这个值之后做旋转显示， 但我们自己如果要画到页面上时就需要对图片做相就的旋转：

google到的：

http://stackoverflow.com/questions/5427656/ios-uiimagepickercontroller-result-image-orientation-after-upload/5427890#5427890

// 自动旋转图片

- (UIImage* )rotateImage:(UIImage *)image {

int kMaxResolution = 320;

// Or whatever

CGImageRef imgRef = image.CGImage;

CGFloat width = CGImageGetWidth(imgRef);

CGFloat height = CGImageGetHeight(imgRef);

CGAffineTransform transform = CGAffineTransformIdentity;

CGRect bounds = CGRectMake(0, 0, width, height);

if (width > kMaxResolution || height > kMaxResolution) {

CGFloat ratio = width  /  height;

if (ratio > 1 ) {

bounds.size.width = kMaxResolution;

bounds.size.height = bounds.size.width / ratio;

}

else {

bounds.size.height = kMaxResolution;

bounds.size.width = bounds.size.height * ratio;

}

}

CGFloat scaleRatio = bounds.size.width / width;

CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));

CGFloat boundHeight;

UIImageOrientation orient = image.imageOrientation;

switch (orient) {

caseUIImageOrientationUp:

//EXIF = 1

transform = CGAffineTransformIdentity;

break;

caseUIImageOrientationUpMirrored:

//EXIF = 2

transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);

transform = CGAffineTransformScale(transform, -1.0, 1.0 );

break;

caseUIImageOrientationDown:

//EXIF = 3

transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);

transform = CGAffineTransformRotate(transform, M_PI);

break;

caseUIImageOrientationDownMirrored:

//EXIF = 4

transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);

transform = CGAffineTransformScale(transform, 1.0, -1.0);

break;

caseUIImageOrientationLeftMirrored:

//EXIF = 5

boundHeight = bounds.size.height;

bounds.size.height = bounds.size.width;

bounds.size.width = boundHeight;

transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width );

transform = CGAffineTransformScale(transform, -1.0, 1.0);

transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0 );

break;

caseUIImageOrientationLeft:

//EXIF = 6

boundHeight = bounds.size.height;

bounds.size.height = bounds.size.width;

bounds.size.width = boundHeight;

transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);

transform = CGAffineTransformRotate( transform, 3.0 * M_PI / 2.0  );

break;

caseUIImageOrientationRightMirrored:

//EXIF = 7

boundHeight = bounds.size.height;

bounds.size.height = bounds.size.width;

bounds.size.width = boundHeight;

transform = CGAffineTransformMakeScale(-1.0, 1.0);

transform = CGAffineTransformRotate( transform, M_PI / 2.0);

break;

caseUIImageOrientationRight:

//EXIF = 8

boundHeight = bounds.size.height;

bounds.size.height = bounds.size.width;

bounds.size.width = boundHeight;

transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);

transform = CGAffineTransformRotate(transform, M_PI / 2.0 );

break;

default:

[NSExceptionraise:NSInternalInconsistencyExceptionformat:@"Invalid image orientation"];

}

UIGraphicsBeginImageContext(bounds.size);

CGContextRef context = UIGraphicsGetCurrentContext();

if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {

CGContextScaleCTM(context, -scaleRatio, scaleRatio);

CGContextTranslateCTM(context, -height, 0);

}

else {

CGContextScaleCTM(context, scaleRatio, -scaleRatio);

CGContextTranslateCTM(context, 0, -height);

}

CGContextConcatCTM(context, transform );

CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);

UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return imageCopy;

}