今天開發一個拍照獲取照片的功能的時候, 發現上傳之后圖片會自動旋轉90.
測試發現, 只要是圖片大于2M, 系統就會自動翻轉照片
相機拍照后直接取出來的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、縮放等操作后，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。imageOrientation是只讀的，不能直接修改其值。
解決方法如下:
1. 設置相機的一個屬性allowsEditing為YES，設了這個值，你拍完照片后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，所以之后的任何裁剪、縮放操作都不會造成旋轉。這是第一種方法。
2. 第一種解決方法基本沒用, 開發中基本都會對圖片進行裁剪和壓縮. 這里有一個專門針對這個事的很好的category
+ (UIImage *)fixOrientation:(UIImage *)aImage { // No-op if the orientation is already correct if (aImage.imageOrientation ==UIImageOrientationUp) return aImage; // We need to calculate the proper transformation to make the image upright. // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored. CGAffineTransform transform =CGAffineTransformIdentity; switch (aImage.imageOrientation) { caseUIImageOrientationDown: caseUIImageOrientationDownMirrored: transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height); transform = CGAffineTransformRotate(transform, M_PI); break; caseUIImageOrientationLeft: caseUIImageOrientationLeftMirrored: transform = CGAffineTransformTranslate(transform, aImage.size.width,0); transform = CGAffineTransformRotate(transform, M_PI_2); break; caseUIImageOrientationRight: caseUIImageOrientationRightMirrored: transform = CGAffineTransformTranslate(transform, 0, aImage.size.height); transform = CGAffineTransformRotate(transform, -M_PI_2); break; default: break; } switch (aImage.imageOrientation) { caseUIImageOrientationUpMirrored: caseUIImageOrientationDownMirrored: transform = CGAffineTransformTranslate(transform, aImage.size.width,0); transform = CGAffineTransformScale(transform, -1, 1); break; caseUIImageOrientationLeftMirrored: caseUIImageOrientationRightMirrored: transform = CGAffineTransformTranslate(transform, aImage.size.height,0); transform = CGAffineTransformScale(transform, -1, 1); break; default: break; } // Now we draw the underlying CGImage into a new context, applying the transform // calculated above. CGContextRef ctx =CGBitmapContextCreate(NULL, aImage.size.width, aImage.size.height, CGImageGetBitsPerComponent(aImage.CGImage),0, CGImageGetColorSpace(aImage.CGImage), CGImageGetBitmapInfo(aImage.CGImage)); CGContextConcatCTM(ctx, transform); switch (aImage.imageOrientation) { caseUIImageOrientationLeft: caseUIImageOrientationLeftMirrored: caseUIImageOrientationRight: caseUIImageOrientationRightMirrored: // Grr... CGContextDrawImage(ctx,CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage); break; default: CGContextDrawImage(ctx,CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage); break; } // And now we just create a new UIImage from the drawing context CGImageRef cgimg =CGBitmapContextCreateImage(ctx); UIImage *img = [UIImageimageWithCGImage:cgimg]; CGContextRelease(ctx); CGImageRelease(cgimg); return img;}以上所述是小編給大家介紹的iOS拍照后圖片自動旋轉90度的完美解決方法，希望對大家有所幫助，如果大家有任何疑問請給我留言，小編會及時回復大家的。在此也非常感謝大家對VEVB武林網網站的支持！
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