ios - 调用“UIImagePickerController didFinishPickingMediaWithInfo”iOS7 XCode 时占用大量 CPU

Question

当我在 UIImagePickerController 上按“使用照片”调用正确的方法时，我注意到 CPU 使用率很高：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{

}

即使方法是空的！此处调用上述方法时记录 CPU 使用情况的图像。

我记录的最高值为 169%。所以wtf？！？

Answer 1

这是因为您使用的图像尺寸非常大，通常超过 2mb。所以在使用之前调整图像大小。这是代码片段：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
    if([[info objectForKey:UIImagePickerControllerMediaType] isEqualToString:@"public.image"]) {
    UIImage *originalImage = info[UIImagePickerControllerOriginalImage];

    if (!originalImage)
        return;

    // Optionally set a placeholder image here while resizing happens in background

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        // Set desired maximum height and calculate width
        CGFloat height = 640.0f;  // or whatever you need
        CGFloat width = (height / self.view.frame.size.height) * self.view.frame.size.width;

        // Resize the image
        UIImage * image = [originalImage resizedImage:CGSizeMake(width, height) interpolationQuality:kCGInterpolationDefault];

        //save/use the image here
        UIImageWriteToSavedPhotosAlbum(image, nil, nil, NULL);//for saving to camera roll
    });
}
}