在 iOS WebView 中横向上传图像

Question

我的 iOS 应用程序的 WebView 中有一个用户注册表单。

该表单允许用户从他们的设备上传图片，但是大约 50% 的用户在上传时将他们的图片横向旋转（或上下颠倒）。

如何强制方向保持与设备照片流中显示的相同？

Answer 1

我使用这个类别来修复图像方向：

- (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;
    case UIImageOrientationUp:
    case UIImageOrientationUpMirrored:
      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;
    case UIImageOrientationUp:
    case UIImageOrientationDown:
    case UIImageOrientationLeft:
    case UIImageOrientationRight:
      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;
}