iphone – imageOrientation返回Up,但照片显示颠倒

发布时间：2020-12-14 19:54:26 所属栏目：百科来源：网络整理

导读：我正在从iPad照片库中抓取一些照片.我在横向模式下拍了几张测试照片,左边是iPad主页按钮,右边是. 所以在我的应用程序中,由于某种原因,一些照片显示为颠倒.我检查了他们的imageOrientation属性,它们都是0(意思是它们是UIImageOrientationUp).这意味着我甚至不

我正在从iPad照片库中抓取一些照片.我在横向模式下拍了几张测试照片,左边是iPad主页按钮,右边是.

所以在我的应用程序中,由于某种原因,一些照片显示为颠倒.我检查了他们的imageOrientation属性,它们都是0(意思是它们是UIImageOrientationUp).这意味着我甚至不知道我需要旋转哪些照片.

发生了什么,我怎么知道哪些照片需要旋转？谢谢

解决方法

UIImage有一个属性imageOrientation,它指示UIImageView和其他UIImage使用者旋转原始图像数据.这个标志很有可能被保存到上传的jpeg图像中的exif数据,但是用来查看它的程序并没有遵守该标志.

要在上传时旋转UIImage以正确显示,您可以使用如下类别：
在.h文件中

UIImagefixOrientation.h

@interface UIImage (fixOrientation)

- (UIImage *)fixOrientation;

@end

UIImagefixOrientation.m

@implementation UIImage (fixOrientation)

- (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,0);
        transform = CGAffineTransformRotate(transform,M_PI_2);
        break;

    case UIImageOrientationRight:
    case UIImageOrientationRightMirrored:
        transform = CGAffineTransformTranslate(transform,self.size.height);
        transform = CGAffineTransformRotate(transform,-M_PI_2);
        break;
}

switch (self.imageOrientation) {
    case UIImageOrientationUpMirrored:
    case UIImageOrientationDownMirrored:
        transform = CGAffineTransformTranslate(transform,0);
        transform = CGAffineTransformScale(transform,-1,1);
        break;

    case UIImageOrientationLeftMirrored:
    case UIImageOrientationRightMirrored:
        transform = CGAffineTransformTranslate(transform,self.size.height,1);
        break;
}

// Now we draw the underlying CGImage into a new context,applying the transform
// calculated above.
CGContextRef ctx = CGBitmapContextCreate(NULL,CGImageGetBitsPerComponent(self.CGImage),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,self.size.width),self.CGImage);
        break;

    default:
        CGContextDrawImage(ctx,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;
}

@end

并在捕获图像保存期间调用此函数或从库中选择图像.

（编辑：李大同）

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