在iOS WebView中上傳圖片

Question

我在iOS應用程序的WebView中有一個用戶註冊表單。

該表格允許用戶從他們的設備上傳圖片，但是當上傳時，大約50％的用戶將圖片橫向（或顛倒）旋轉。

如何強制使其方向與設備照片流中出現的方向保持一致？

Answer 1

我使用這個類來修復形象定位：

- (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; 
}