3a: AEC Multi-window metering mode implementation

 Mapping user specified Multi metering weighting windows to
 RGB statistic grid, AEC algorithum uses this information
 to calculate a weighted histogram to get accurate AEC calculation.

 * User can set multiple arbitrary metering windows (both size and
   coordinator) inside of image frame dynamically.
 * The maximum metering window count is defined in source code,
   currently defined as 6, it can be more.
 * Overlap metering window weighting is not supported yet, the last
   window’s weighting factor will overwrite the former one in the
   overlapped region.
 * User should assign 0 ~ 15 weighting factor to each metering
   window, the pixel weighted by 0 will not take into account in
   AEC calculation.

Signed-off-by: Wind Yuan <feng.yuan@intel.com>
11 files changed