图像编辑或选取照片后的方向旋转

问题描述：选取相册图片或使用摄像头拍摄图片后，得到的图像旋转90度

解决方法：在获取图片，使用之前，调整图像的方向属性

结果：正常运行

相关函数：

CGAffineTransformTranslate(transform, x, y):改变位置，

CGAffineTransformMakeTranslation(width, 0.0);改变位置，

CGAffineTransformRotate(transform, M_PI);旋转。

CGAffineTransformMakeRotation(-M_PI);旋转的

transform = CGAffineTransformScale(transform, -1.0, 1.0);是缩放的。

?view.transform = CGAffineTransformIdentity;当改变过一个view.transform属性或者view.layer.transform的时候需要恢复默认状态的话，记得先把他们重置可以使用

view.transform = CGAffineTransformIdentity，

或者view.layer.transform = CATransform3DIdentity，

 

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扩展UIImage类，增加新方法fixOrientation以使图像回归正确的方向属性

UIImage+fixOrientation.h

#import <UIKit/UIKit.h>

@interface UIImage (fixOrientation)

- (UIImage *)fixOrientation;

@end

 UIImage+fixOrientation.m

 

#import "UIImage+fixOrientation.h"

 

@implementation UIImage (fixOrientation)

- (UIImage *)fixOrientation {

    

    // 如果图像已经是正确方向则不做操作

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

    

    // 否则执行对应的操作以调整方向

    // 1，旋转 2，翻转

    CGAffineTransform transform = CGAffineTransformIdentity;

    

    switch (self.imageOrientation) {

        case UIImageOrientationDown://方向向下

        case UIImageOrientationDownMirrored://方向下并且被翻转

            transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height);//移动至右下角

            transform = CGAffineTransformRotate(transform, M_PI);//以右下角为圆点旋转180度

            break;//更改结果，方向朝上

            

        case UIImageOrientationLeft://方向向左

        case UIImageOrientationLeftMirrored://方向向左并且翻转

            transform = CGAffineTransformTranslate(transform, self.size.width, 0);//右移width

            transform = CGAffineTransformRotate(transform, M_PI_2);//逆时针旋转90度

            break;

            

        caseUIImageOrientationRight://方向向右

        caseUIImageOrientationRightMirrored://方向向右并且翻转

            transform = CGAffineTransformTranslate(transform, 0, self.size.height);//下移

            transform = CGAffineTransformRotate(transform, -M_PI_2);//顺时针旋转-90度

            break;

    }

    

    switch (self.imageOrientation) {

        case UIImageOrientationUpMirrored://向上镜像

        case UIImageOrientationDownMirrored://向下镜像

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

            transform = CGAffineTransformScale(transform, -1, 1);//纵向翻转

            break;

            

        case UIImageOrientationLeftMirrored://向左镜像

        case UIImageOrientationRightMirrored:向右镜像

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

            transform = CGAffineTransformScale(transform, -1, 1);//横向翻转

            break;

    }

    

    // Now we draw the underlying CGImage into a new context, applying the transform

    // calculated above.

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

                                             CGImageGetBitsPerComponent(self.CGImage), 0,

                                             CGImageGetColorSpace(self.CGImage),

                                             CGImageGetBitmapInfo(self.CGImage));

    CGContextConcatCTM(ctx, transform);

    switch (self.imageOrientation) {

        case UIImageOrientationLeft:

        case UIImageOrientationLeftMirrored:

        case UIImageOrientationRight:

        case UIImageOrientationRightMirrored:

            // Grr...

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

            break;

            

        default:

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

}