Вы можете масштабировать растровые изображения следующим образом:
// Load in your bitmap here, I'll leave this detail up to you
Bitmap _bitmapPreScale = BitmapFactory.decodeResource(resources, fieldValue);
int oldWidth = _bitmapPreScale.getWidth();
int oldHeight = _bitmapPreScale.getHeight();
int newWidth = width; // whatever your desired width and height are
int newHeight = height;
// calculate the scale
float scaleWidth = ((float) newWidth) / oldWidth;
float scaleHeight = ((float) newHeight) / oldHeight;
// create a matrix for the manipulation
Matrix matrix = new Matrix();
// resize the bit map
matrix.postScale(scaleWidth, scaleHeight);
// recreate the new Bitmap
Bitmap _bitmapScaled = Bitmap.createBitmap(_bitmapPreScale, 0, 0, oldWidth, oldHeight, matrix, true);