AVCaptureSession设置的是
AVCaptureSessionPresetPhoto，也就是New iPad摄像头最大分辨率2592*1936.但是capture得到的比率确实1936*2592.
这里描述了相同的问题:
我参照http://blog.logichigh.com/2008/06/05/uiimage-fix/得到了解决
转换代码如下:
1 UIImage *scaleAndRotateImage(UIImage *image) 2 { 3 int kMaxResolution = 2592; // Or whatever 4 5 CGImageRef imgRef = image.CGImage; 6 7 CGFloat width = CGImageGetWidth(imgRef); 8 CGFloat height = CGImageGetHeight(imgRef); 9 10 CGAffineTransform transform = CGAffineTransformIdentity; 11 CGRect bounds = CGRectMake(0, 0, width, height); 12 if (width > kMaxResolution || height > kMaxResolution) { 13 CGFloat ratio = width/height; 14 if (ratio > 1) { 15 bounds.size.width = kMaxResolution; 16 bounds.size.height = bounds.size.width / ratio; 17 } 18 else { 19 bounds.size.height = kMaxResolution; 20 bounds.size.width = bounds.size.height * ratio; 21 } 22 } 23 24 CGFloat scaleRatio = bounds.size.width / width; 25 CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef)); 26 CGFloat boundHeight; 27 UIImageOrientation orient = image.imageOrientation; 28 switch(orient) { 29 30 case UIImageOrientationUp: //EXIF = 1 31 transform = CGAffineTransformIdentity; 32 break; 33 34 case UIImageOrientationUpMirrored: //EXIF = 2 35 transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0); 36 transform = CGAffineTransformScale(transform, -1.0, 1.0); 37 break; 38 39 case UIImageOrientationDown: //EXIF = 3 40 transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height); 41 transform = CGAffineTransformRotate(transform, M_PI); 42 break; 43 44 case UIImageOrientationDownMirrored: //EXIF = 4 45 transform = CGAffineTransformMakeTranslation(0.0, imageSize.height); 46 transform = CGAffineTransformScale(transform, 1.0, -1.0); 47 break; 48 49 case UIImageOrientationLeftMirrored: //EXIF = 5 50 boundHeight = bounds.size.height; 51 bounds.size.height = bounds.size.width; 52 bounds.size.width = boundHeight; 53 transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width); 54 transform = CGAffineTransformScale(transform, -1.0, 1.0); 55 transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0); 56 break; 57 58 case UIImageOrientationLeft: //EXIF = 6 59 boundHeight = bounds.size.height; 60 bounds.size.height = bounds.size.width; 61 bounds.size.width = boundHeight; 62 transform = CGAffineTransformMakeTranslation(0.0, imageSize.width); 63 transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0); 64 break; 65 66 case UIImageOrientationRightMirrored: //EXIF = 7 67 boundHeight = bounds.size.height; 68 bounds.size.height = bounds.size.width; 69 bounds.size.width = boundHeight; 70 transform = CGAffineTransformMakeScale(-1.0, 1.0); 71 transform = CGAffineTransformRotate(transform, M_PI / 2.0); 72 break; 73 74 case UIImageOrientationRight: //EXIF = 8 75 boundHeight = bounds.size.height; 76 bounds.size.height = bounds.size.width; 77 bounds.size.width = boundHeight; 78 transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0); 79 transform = CGAffineTransformRotate(transform, M_PI / 2.0); 80 break; 81 82 default: 83 [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"]; 84 85 } 86 87 UIGraphicsBeginImageContext(bounds.size); 88 89 CGContextRef context = UIGraphicsGetCurrentContext(); 90 91 if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) { 92 CGContextScaleCTM(context, -scaleRatio, scaleRatio); 93 CGContextTranslateCTM(context, -height, 0); 94 } 95 else { 96 CGContextScaleCTM(context, scaleRatio, -scaleRatio); 97 CGContextTranslateCTM(context, 0, -height); 98 } 99 100 CGContextConcatCTM(context, transform); 101 102 CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef); 103 UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext(); 104 UIGraphicsEndImageContext(); 105 106 return imageCopy; 107 }