如何防止保存到照片库的图像被调整大小/缩放为全屏？

Question

Here is the deal, I have tried using both of the methods shown below to save an image to the photo library. Upon saving the image successfully and launching the Photos App to take a look at the image, the app automatically scales/resizes the image to full screen.

Is there any way to prevent this? It is annoying because to see the whole image the user needs to pinch the image out to show the whole thing. I have noticed a few of the more popular camera apps do not have this issue when saving to the photo library. I am curious what method they are using.

//Save to Photo Library;
ALAssetsLibrary* library = [[ALAssetsLibrary alloc] init];
//CIImage *ciImage = image.CIImage;
[library writeImageToSavedPhotosAlbum:finalImage.CGImage
                          orientation:ALAssetOrientationUp
                      completionBlock:^(NSURL *assetURL, NSError *error) {
                          NSlog(@"Done");
                      }];

Save to Photo Library;
UIImageWriteToSavedPhotosAlbum(savedPhoto,nil,nil,nil);

Thank you for your help!

Answer 1

After doing a bit of research there is no solution to this problem. The photos app automatically scales up the image to fill the screen.

Thanks for all of the responses.

Answer 2

Saving image should be fine.

I think you can set UIView property UIViewContentMode, when you using the image.

typedef enum {
UIViewContentModeScaleToFill,
UIViewContentModeScaleAspectFit,      // contents scaled to fit with fixed aspect. remainder is transparent
UIViewContentModeScaleAspectFill,     // contents scaled to fill with fixed aspect. some portion of content may be clipped.
UIViewContentModeRedraw,              // redraw on bounds change (calls -setNeedsDisplay)
UIViewContentModeCenter,              // contents remain same size. positioned adjusted.
UIViewContentModeTop,
UIViewContentModeBottom,
UIViewContentModeLeft,
UIViewContentModeRight,
UIViewContentModeTopLeft,
UIViewContentModeTopRight,
UIViewContentModeBottomLeft,
UIViewContentModeBottomRight,

} UIViewContentMode;

Hope it helps.

Answer 3

If you take a look at the FrogScroller sample application from Apple, you'll see they initially load a low-resolution of the image first and then, when zooming use a CATiledLayer with it's size set by the setMaxMinZoomScalesForCurrentBounds function.

You might want to look at WWDC 2010's video on scrollViews as well as 2011 for more info. Josh and Eliza do a great job explaining what's up.

Answer 4

为什么在保存之前不将图像分层到具有清晰背景的全屏图像上？