iOS开发- 相机(摄像头)获取到的图片自动旋转90度解决办法无标题文章

用相机拍摄出来的照片含有EXIF信息,UIImage的imageOrientation属性指的就是EXIF中的orientation信息。

果我们忽略orientation信息,而直接对照片进行像素处理或者drawInRect等操作,得到的结果是翻转或者旋转90之后的样子。这是因为我

们执行像素处理或者drawInRect等操作之后,imageOrientaion信息被删除了,imageOrientaion被重设为0,造成照片

内容和imageOrientaion不匹配。

所以,在对照片进行处理之前,先将照片旋转到正确的方向,并且返回的imageOrientaion为0。

下面这个方法就是一个UIImage category中的方法,用它可以达到以上目的。

- (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) {

case UIImageOrientationDown:

case UIImageOrientationDownMirrored:

transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);

transform = CGAffineTransformRotate(transform, M_PI);

break;

case UIImageOrientationLeft:

case UIImageOrientationLeftMirrored:

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

transform = CGAffineTransformRotate(transform, M_PI_2);

break;

case UIImageOrientationRight:

case UIImageOrientationRightMirrored:

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

transform = CGAffineTransformRotate(transform, -M_PI_2);

break;

default:

break;

}

switch (aImage.imageOrientation) {

case UIImageOrientationUpMirrored:

case UIImageOrientationDownMirrored:

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

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

break;

case UIImageOrientationLeftMirrored:

case UIImageOrientationRightMirrored:

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) {

case UIImageOrientationLeft:

case UIImageOrientationLeftMirrored:

case UIImageOrientationRight:

case UIImageOrientationRightMirrored:

// 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 = [UIImage imageWithCGImage:cgimg];

CGContextRelease(ctx);

CGImageRelease(cgimg);

return img;

}

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