Android pinch zoom large image, memory efficient without losing detail

11
votes

My app has to display a number of high resolution images (about 1900*2200 px), support pinch zoom. To avoid Out of memory error I plan to decode image to show full screen by using

options.inSampleSize = scale (scale was calculated as Power of 2 as Document)

(My view i used is TouchImageView extends of ImageView)

So i can quickly load image and swipe smoothly between screens(images). However, when i pinch zoom, my app loses detail because of scaled image. If i load full image, i can't load quickly or smoothly swipe, drag after pinch zoom. Then i try to only load full image when user begin pinch-zooming, but i still can't drag smoothly image because of very large image. Android gallery can do it perfectly even 8Mpx images.

Anyone can help me. Thanks in advance

2
androidimageviewout-of-memorylarge-filespinchzoom
Maybe that's what you are looking for stackoverflow.com/questions/12022675/decode-part-of-jpeg-file - exebook
I don't understand deeply it but maybe it is not helpful for me - Kiradev
The (seemengly) only way to display huge Jpegs fast is to progressively load them and only decode the required parts. Common way to access jpeg is libjpeg, so the link above discusses how to use libjpeg to get progressively parts of the jpeg file without decoding it as a whole. - exebook
but libjpeg is written by C language. So is there another in Java? - Kiradev
Yes you can call C functions from Java, as explained here. stackoverflow.com/questions/12260149/libjpeg-turbo-for-android - exebook

2 Answers

9
votes

Sorry to answer an old question, but I've just completed an image view that shows an image from assets or external storage with subsampling, and loads higher resolution tiles from the image as you pinch to zoom in. As high resolution image data for areas of the screen is not loaded it should avoid out of memory exceptions.

https://github.com/davemorrissey/subsampling-scale-image-view

3
votes

I know the question was asked a long time ago but this answer might help other people struggling with this. I had exactly the same issue. You should consider using WebView and load your image with it, even if it is a local image. For instance to load an image in assets use the following:

// Get a WebView you have defined in your XML layout    
WebView webView = (WebView) findViewById(R.id.webView1);  
// Fetch the picture in your folders using HTML             
String htmlData = "<img src=\"my_image.png\">";
webView.loadDataWithBaseURL("file:///android_asset/", htmlData, "text/html", "utf-8", null);
// Activate zooming
webView.getSettings().setBuiltInZoomControls(true);

I admit that it is very strange to use WebView for such a task, it is the only solution I found. At least you will never get an OOM exception.