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  • 修正iOS从照相机和相册中获取的图片方向

    使用系统相机拍照得到的图片的默认方向有时不是ImageOrientationDown,而是ImageOrientationLeft,在使用的时候会出现图片顺时针偏转90°。使用fixOrientation方法修正这个问题。

    - (UIImage *)fixOrientation
    {    
        // No-op if the orientation is already correct
        if (self.imageOrientation == UIImageOrientationUp)
            return self;
        
        // 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 (self.imageOrientation) {
            case UIImageOrientationDown:
            case UIImageOrientationDownMirrored:
                transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height);
                transform = CGAffineTransformRotate(transform, M_PI);
                break;
                
            case UIImageOrientationLeft:
            case UIImageOrientationLeftMirrored:
                transform = CGAffineTransformTranslate(transform, self.size.width, 0);
                transform = CGAffineTransformRotate(transform, M_PI_2);
                break;
                
            case UIImageOrientationRight:
            case UIImageOrientationRightMirrored:
                transform = CGAffineTransformTranslate(transform, 0, self.size.height);
                transform = CGAffineTransformRotate(transform, -M_PI_2);
                break;
            default:
                break;
        }
        
        switch (self.imageOrientation) {
            case UIImageOrientationUpMirrored:
            case UIImageOrientationDownMirrored:
                transform = CGAffineTransformTranslate(transform, self.size.width, 0);
                transform = CGAffineTransformScale(transform, -1, 1);
                break;
                
            case UIImageOrientationLeftMirrored:
            case UIImageOrientationRightMirrored:
                transform = CGAffineTransformTranslate(transform, self.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, 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;
    }
    
    
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  • 原文地址:https://www.cnblogs.com/zy1987/p/4454107.html
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