蘋果手機上傳圖片到伺服器，發現圖片方向不對，實踐發現：

1:原因：  相機拍照後直接取出來的UIimage（用UIImagePickerControllerOriginalImage取出），它本身的imageOrientation屬性是3，即UIImageOrientationRight。如果這個圖片直接使用則沒事，但是如果對它進行裁剪、縮放等操作後，它的這個imageOrientation屬性會變成0。此時這張圖片用在別的地方就會發生旋轉。（手機豎著拍則為UIImageOrientationRight，手機橫著拍為UIImageOrientationUp）

2:  imageOrientation是隻讀的，不能直接修改其值。

解決方法：

1. 設定相機的一個屬性allowsEditing為YES，設了這個值，你拍完照片後會在照片上出現一個框框，這就是對照片的裁剪編輯。在相機的代理方法中取照片的時候就別用UIImagePickerControllerOriginalImage來取了，要用UIImagePickerControllerEditedImage。用這個key取出來的照片，它的imageOrientation是0，所以之後的任何裁剪、縮放操作都不會造成旋轉。

2.由於開發中經常要對原圖進行裁剪和壓縮，所以第一種方法就不可取了，於是用第二種方法

//調整圖片方向

+ (UIImage *)fixOrientation:(

if (srcImg.imageOrientation ==UIImageOrientationUp) return srcImg;

CGAffineTransform transform =CGAffineTransformIdentity;

switch (srcImg.imageOrientation) {

caseUIImageOrientationDown:

caseUIImageOrientationDownMirrored:

            transform = CGAffineTransformTranslate(transform, srcImg.

            transform = CGAffineTransformRotate(transform,M_PI);

break;

caseUIImageOrientationLeft:

caseUIImageOrientationLeftMirrored:

            transform = CGAffineTransformTranslate(transform, srcImg.size.width,0);

            transform = CGAffineTransformRotate(transform,M_PI_2);

break;

caseUIImageOrientationRight:

caseUIImageOrientationRightMirrored:

            transform = CGAffineTransformTranslate(transform,0, srcImg.size.height);

            transform = CGAffineTransformRotate(transform, -M_PI_2);

break;

caseUIImageOrientationUp:

caseUIImageOrientationUpMirrored:

break;

    }

switch (srcImg.imageOrientation) {

caseUIImageOrientationUpMirrored:

caseUIImageOrientationDownMirrored:

            transform = CGAffineTransformTranslate(transform, srcImg.size.width,0);

            transform = CGAffineTransformScale(transform, -1,1);

break;

caseUIImageOrientationLeftMirrored:

caseUIImageOrientationRightMirrored:

            transform = CGAffineTransformTranslate(transform, srcImg.size.height,0);

            transform = CGAffineTransformScale(transform, -1,1);

break;

caseUIImageOrientationUp:

caseUIImageOrientationDown:

caseUIImageOrientationLeft:

caseUIImageOrientationRight:

break;

    }

CGContextRef ctx =CGBitmapContextCreate(NULL, srcImg.size.width, srcImg.size.height,

CGImageGetBitsPerComponent(srcImg.CGImage),0,

CGImageGetColorSpace(srcImg.CGImage),

CGImageGetBitmapInfo(srcImg.CGImage));

CGContextConcatCTM(ctx, transform);

switch (srcImg.imageOrientation) {

caseUIImageOrientationLeft:

caseUIImageOrientationLeftMirrored:

caseUIImageOrientationRight:

caseUIImageOrientationRightMirrored:

CGContextDrawImage(ctx,CGRectMake(0,0,srcImg.size.height,srcImg.size.width), srcImg.CGImage);

break;

default:

CGContextDrawImage(ctx,CGRectMake(0,0,srcImg.size.width,srcImg.size.height), srcImg.CGImage);

break;

    }

CGImageRef cgimg =CGBitmapContextCreateImage(ctx);

UIImage *img = [UIImageimageWithCGImage:cgimg];

CGContextRelease(ctx);

CGImageRelease(cgimg);

return img;

}