android - How to efficiently decode a image knowing only its path -

i'm creating own gallery using viewpager, 'connected' arraylist holding paths of images display.

so far, use:

bitmap bitmap = bitmapfactory.decodefile(path); imageview.setimagebitmap(bitmap); imageview.setscaletype(imageview.scaletype.center_inside); 

it's working, pictures pretty big , unnecessarily decode whole picture, because it's scaled down later fit layout. slow , crash outofmemoryerror happens sometimes, when scroll fast.

so question is: how can efficiently decode image fits 100% imageview.scaletype.center_inside knowing path?

do not decode directy. use injustdecodebounds = true bitmapfactory.options, load width , height bitmap. can calcuate insamplesize scale bitmap

bitmapfactory.options options = new bitmapfactory.options(); options.injustdecodebounds = true; bitmapfactory.decodefile(path, options); 

decodefile return null , options contains width , height. calculate insamplesize and:

bitmapfactory.options options = new bitmapfactory.options(); options.injustdecodebounds = false; options.insamplesize = myinsamplesize; bitmap output = bitmapfactory.decodefile(path, options);