问题
I want to load images from UIImagePickerController, then save the selected photo to my app's document directory.
UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
NSData *data1 = UIImagePNGRepresentation(image);
NSString *fileName = "1.png";
NSString *path = //get Document path, then add fileName
BOOL succ = [data1 writeToFile:path atomically:YES];
but after I save the image to my document, I found that, the image was rotated 90 degree, then I change the method UIImagePNGRepresentation to UIImageJPEGRepresentation, this time it's fine, anyone know what's the problem?
回答1:
I had the same problem and just figured out the reason: starting with iOS 4.0 when the camera takes a photo it does not rotate it before saving, it simply sets a rotation flag in the EXIF data of the JPEG.
If you save a UIImage as a JPEG, it will set the rotation flag.
PNGs do not support a rotation flag, so if you save a UIImage as a PNG, it will be rotated incorrectly and not have a flag set to fix it. So if you want PNGs you must rotate them yourself.
I would call this a bug in the PNG saving function but that's just an opinion (they should at least warn you about this).
回答2:
Please try this one.
func rotateImage(image: UIImage) -> UIImage? {
if (image.imageOrientation == UIImage.Orientation.up ) {
return image
}
UIGraphicsBeginImageContext(image.size)
image.draw(in: CGRect(origin: CGPoint.zero, size: image.size))
let copy = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return copy
}
Happy Codding :)
回答3:
I solve this issue with the following code.
- (UIImage *)scaleAndRotateImage:(UIImage *)image
{
int kMaxResolution = 640;
CGImageRef imgRef = image.CGImage;
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);
CGAffineTransform transform = CGAffineTransformIdentity;
CGRect bounds = CGRectMake(0, 0, width, height);
if (width > kMaxResolution || height > kMaxResolution) {
CGFloat ratio = width/height;
if (ratio > 1) {
bounds.size.width = kMaxResolution;
bounds.size.height = bounds.size.width / ratio;
}
else {
bounds.size.height = kMaxResolution;
bounds.size.width = bounds.size.height * ratio;
}
}
CGFloat scaleRatio = bounds.size.width / width;
CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
CGFloat boundHeight;
UIImageOrientation orient = image.imageOrientation;
switch(orient) {
case UIImageOrientationUp: //EXIF = 1
transform = CGAffineTransformIdentity;
break;
case UIImageOrientationUpMirrored: //EXIF = 2
transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
transform = CGAffineTransformScale(transform, -1.0, 1.0);
break;
case UIImageOrientationDown: //EXIF = 3
transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
transform = CGAffineTransformRotate(transform, M_PI);
break;
case UIImageOrientationDownMirrored: //EXIF = 4
transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
transform = CGAffineTransformScale(transform, 1.0, -1.0);
break;
case UIImageOrientationLeftMirrored: //EXIF = 5
boundHeight = bounds.size.height;
bounds.size.height = bounds.size.width;
bounds.size.width = boundHeight;
transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
transform = CGAffineTransformScale(transform, -1.0, 1.0);
transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
break;
case UIImageOrientationLeft: //EXIF = 6
boundHeight = bounds.size.height;
bounds.size.height = bounds.size.width;
bounds.size.width = boundHeight;
transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
break;
case UIImageOrientationRightMirrored: //EXIF = 7
boundHeight = bounds.size.height;
bounds.size.height = bounds.size.width;
bounds.size.width = boundHeight;
transform = CGAffineTransformMakeScale(-1.0, 1.0);
transform = CGAffineTransformRotate(transform, M_PI / 2.0);
break;
case UIImageOrientationRight: //EXIF = 8
boundHeight = bounds.size.height;
bounds.size.height = bounds.size.width;
bounds.size.width = boundHeight;
transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
transform = CGAffineTransformRotate(transform, M_PI / 2.0);
break;
default:
[NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];
}
UIGraphicsBeginImageContext(bounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
CGContextScaleCTM(context, -scaleRatio, scaleRatio);
CGContextTranslateCTM(context, -height, 0);
}
else {
CGContextScaleCTM(context, scaleRatio, -scaleRatio);
CGContextTranslateCTM(context, 0, -height);
}
CGContextConcatCTM(context, transform);
CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return imageCopy;
}
回答4:
The following swift function resolves the problem.
func rotateImage(image: UIImage) -> UIImage? {
if (image.imageOrientation == UIImage.Orientation.up ) {
return image
}
UIGraphicsBeginImageContext(image.size)
image.draw(in: CGRect(origin: CGPoint.zero, size: image.size))
let copy = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return copy
}
Yup it is that simple, just because the drawInRect function will take image orientation in consideration.
回答5:
I have created this UIImage extension to fix this problem with UIImagePNGRepresentation, based on this response. So I propose to use this class func UIImage.PNGRepresentation(img: UIImage) instead of UIKit func UIImagePNGRepresentation.
Swift 3 code :
// MyUIImage.swift
// MyEasyMovie-Public-App
//
// Created by Ahmed Zahraz on 19/12/2016.
// Copyright © 2016 AhmedZahraz. All rights reserved.
import Foundation
import UIKit
extension UIImage {
public class func PNGRepresentation(_ img: UIImage) -> Data? {
// No-op if the orientation is already correct
if (img.imageOrientation == UIImageOrientation.up) {
return UIImagePNGRepresentation(img);
}
// 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.
var transform:CGAffineTransform = CGAffineTransform.identity
if (img.imageOrientation == UIImageOrientation.down
|| img.imageOrientation == UIImageOrientation.downMirrored) {
transform = transform.translatedBy(x: img.size.width, y: img.size.height)
transform = transform.rotated(by: CGFloat(M_PI))
}
if (img.imageOrientation == UIImageOrientation.left
|| img.imageOrientation == UIImageOrientation.leftMirrored) {
transform = transform.translatedBy(x: img.size.width, y: 0)
transform = transform.rotated(by: CGFloat(M_PI_2))
}
if (img.imageOrientation == UIImageOrientation.right
|| img.imageOrientation == UIImageOrientation.rightMirrored) {
transform = transform.translatedBy(x: 0, y: img.size.height);
transform = transform.rotated(by: CGFloat(-M_PI_2));
}
if (img.imageOrientation == UIImageOrientation.upMirrored
|| img.imageOrientation == UIImageOrientation.downMirrored) {
transform = transform.translatedBy(x: img.size.width, y: 0)
transform = transform.scaledBy(x: -1, y: 1)
}
if (img.imageOrientation == UIImageOrientation.leftMirrored
|| img.imageOrientation == UIImageOrientation.rightMirrored) {
transform = transform.translatedBy(x: img.size.height, y: 0);
transform = transform.scaledBy(x: -1, y: 1);
}
// Now we draw the underlying CGImage into a new context, applying the transform
// calculated above.
let ctx:CGContext = CGContext(data: nil, width: Int(img.size.width), height: Int(img.size.height),
bitsPerComponent: img.cgImage!.bitsPerComponent, bytesPerRow: 0,
space: img.cgImage!.colorSpace!,
bitmapInfo: img.cgImage!.bitmapInfo.rawValue)!
ctx.concatenate(transform)
if (img.imageOrientation == UIImageOrientation.left
|| img.imageOrientation == UIImageOrientation.leftMirrored
|| img.imageOrientation == UIImageOrientation.right
|| img.imageOrientation == UIImageOrientation.rightMirrored
) {
ctx.draw(img.cgImage!, in: CGRect(x:0,y:0,width:img.size.height,height:img.size.width))
} else {
ctx.draw(img.cgImage!, in: CGRect(x:0,y:0,width:img.size.width,height:img.size.height))
}
// And now we just create a new UIImage from the drawing context
let cgimg:CGImage = ctx.makeImage()!
let imgEnd:UIImage = UIImage(cgImage: cgimg)
return UIImagePNGRepresentation(imgEnd)
}
}
回答6:
Stefan's answer updated for Swift 4:
func rotateImage(image: UIImage) -> UIImage {
if (image.imageOrientation == UIImage.Orientation.up) {
return image
}
UIGraphicsBeginImageContext(image.size)
image.draw(in: CGRect(origin: .zero, size: image.size))
let copy = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return copy!
}
And then:
var originalImage = yourImage.image!
image = rotateImage(image: originalImage)
来源：https://stackoverflow.com/questions/3554244/uiimagepngrepresentation-issues-images-rotated-by-90-degrees