问题
今天在做项目的时候发现, 如果把通过相机获取到的图片，直接进行操作, 比如裁剪, 缩放, 则会把原图片向又旋转90度。
产生原因
1、如果该图片大于2M，会自动旋转90度；否则不旋转
UIImage* originalImg=[dict objectForKey:UIImagePickerControllerOriginalImage];
2、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。如果我们忽略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。
解决办法
在UIImage Category中写一个处理图片方向的方法，然后在相机拍照获取到图片后调用，就可以解决原始图片旋转90度的问题了，下面是UIImage类别的方法源码，可直接复制调用哦。
+ (UIImage*)fixOrientation:(UIImage*)image
{
if (image.imageOrientation == UIImageOrientationUp)
return image;
CGAffineTransform transform = CGAffineTransformIdentity;
switch (image.imageOrientation) {
case UIImageOrientationDown:
case UIImageOrientationDownMirrored:
transform =CGAffineTransformTranslate(transform, image.size.width, image.size.height);
transform =CGAffineTransformRotate(transform,M_PI);
break;
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
transform =CGAffineTransformTranslate(transform, image.size.width,0);
transform =CGAffineTransformRotate(transform,M_PI_2);
break;
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
transform =CGAffineTransformTranslate(transform,0, image.size.height);
transform =CGAffineTransformRotate(transform, -M_PI_2);
break;
default:
break;
}
switch (image.imageOrientation) {
case UIImageOrientationUpMirrored:
case UIImageOrientationDownMirrored:
transform =CGAffineTransformTranslate(transform, image.size.width,0);
transform =CGAffineTransformScale(transform, -1,1);
break;
case UIImageOrientationLeftMirrored:
case UIImageOrientationRightMirrored:
transform =CGAffineTransformTranslate(transform, image.size.height,0);
transform =CGAffineTransformScale(transform, -1,1);
break;
default:
break;
}
CGContextRef ctx = CGBitmapContextCreate(NULL, image.size.width, image.size.height,
CGImageGetBitsPerComponent(image.CGImage),0,
CGImageGetColorSpace(image.CGImage),
CGImageGetBitmapInfo(image.CGImage));
CGContextConcatCTM(ctx, transform);
switch (image.imageOrientation) {
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
// Grr...
CGContextDrawImage(ctx,CGRectMake(0,0,image.size.height,image.size.width), image.CGImage);
break;
default:
CGContextDrawImage(ctx,CGRectMake(0,0,image.size.width,image.size.height), image.CGImage);
break;
}
CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
UIImage*img = [UIImage imageWithCGImage:cgimg];
CGContextRelease(ctx);
CGImageRelease(cgimg);
return img;
}