i am working on image ,upload original image in this original image resize the small image this image saved in to database
original image --> resize it (small image )--
To do this you'll want to play around with the Bitmap class.
It has several functions to create new bitmaps form previous ones
Bitmap bmp2 = Bitmap.createScaledBitmap(bmp, width, height, true);
a full list can be found in the documentation :
http://developer.android.com/reference/android/graphics/Bitmap.html
Regarding the save to a database I've never done but it would depend on your server.