android - Is it possible to chop a bitmap to small pieces without loading the entire thing into memory?

Question

I'm working on an image processing application for Android that recognizes music notation from pictures taken of music sheets.

I tried to load the entire image into a Bitmap using the BitmapFactory.decodeFile(imgPath) method, but because my phone doesn't have enough memory I get a "VM heap size" error. To work around this, I'd like to chop the full image into smaller pieces, but I'm not sure how to do that.

I also saw that it was possible to reduce the memory size of the Bitmap by using the inSampleSize property of the BitmapFactory.Option class, but if I do that I won't get the high resolution image I need for the music notation recognition process.

Is there anyway to handle this without going to NDK?

Answer 1

Android 2.3.3 has a new API called android.graphics.BitmapRegionDecoder that lets you do exactly what you want.

You would for instance do the following:

BitmapRegionDecoder decoder = BitmapRegionDecoder.newInstance(myStream, false);
Bitmap region = decoder.decodeRegion(new Rect(10, 10, 50, 50), null);

Easy :)