使用UIImagePickerController获取图像-如何知道是否保存PNG或JPEG? [英] Using UIImagePickerController to get image -- how to know whether to save PNG or JPEG?

问题描述

我有一个UIImagePickerController，允许用户从图像库中选择一个图像，并通过didFinishPickingMediaWithInfo方法获得其结果.

I've got a UIImagePickerController letting the user pick an image out of the image library, and am getting its results via the didFinishPickingMediaWithInfo method.

我需要能够将生成的图像保存到磁盘(在应用程序的documents文件夹中)，并在以后重新加载.

I need to be able to save the resulting image to disk (in the app's documents folder), and reload it later.

问题是我不知道是否将其存储为PNG或JPEG.我不能总是将其存储为PNG，因为对于较大的照片，它的运行速度非常慢(更不用说我必须单独存储图像方向).我不能总是将其存储为JPEG，因为在某些情况下图像具有透明度，如果这样做会丢失.

The issue is that I can't tell whether to store it as a PNG or JPEG. I can't just always store it as a PNG, because for larger photos it's interminably slow (not to mention then I have to deal with storing the image orientation separately). I can't just always store it as a JPEG, because in some cases the images have transparency, which will get lost if I do that.

我已经检查了图像选择器返回的信息词典中的UIImagePickerControllerMediaType键，无论选择了PNG还是JPEG，返回的都是"image.public".

I've examined the UIImagePickerControllerMediaType key in the info dictionary returned by the image picker, and regardless of whether I've selected a PNG or JPEG, what gets returned is "image.public".

所以...

是否可以通过某种方式知道用户是否选择了PNG?也许只是一些方法来检查图像是否具有透明度或其他功能?

Is there some way to know whether the user has chosen a PNG? Maybe some method of just checking if the image has any transparency or something?

谢谢.

推荐答案

在字典中，键UIImagePickerControllerReferenceURL将为您提供有关类型的信息

in the dictionary the key UIImagePickerControllerReferenceURL will give you informations about the type

(gdb)订单信息

{
    UIImagePickerControllerMediaType = "public.image";
    UIImagePickerControllerOriginalImage = "<UIImage: 0x5cfd00>";
    UIImagePickerControllerReferenceURL = "assets-library://asset/asset.JPG?id=EFC44C3C-9C82-4669-924B-A2B9DE6F1F45&ext=JPG";
}

在这种情况下，它是ext = JPG所示的jpg

In this case it is a jpg as shown by ext=JPG

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