You can initialize a bitmap with the file, thus having the size of the image, and then allocate this bitmap to the imageview.
Alternatively - use jpeg library with LoadJpegSizeOnly, then you can set the imageview to the same size and set the image to it.
If the imageview size is fix, you have to draw part of the full image using canvas and drawbitmap, with the source rectangle size set to the imageview size and the origin is set as you wish - starting from the top-left corner or centered ...