Image processing device with automatic white balance

Abstract

According to one aspect of the present invention, there is provided a digital camera system being capable of taking a frame of image data comprising a plurality of color elements, the system being arranged: to divide the frame image data into a plurality of blocks including a plurality of pixel data; to calculate a predetermined value for the each color element and for each of all or a part of the plurality of blocks; to judge, for each of all or a part of the plurality of blocks, whether the block being likely a part of a grey object or not to cumulate the predetermined values of the blocks judged as being likely a part of a gray object for the respective color elements, and; to decide a first set of digital gains for adjusting white balance based on the cumulated values.

1 . A digital camera system being capable of taking a frame of image data comprising a plurality of color elements, the system being arranged: 
 to divide the frame image data into a plurality of blocks including a plurality of pixel data;    to calculate a predetermined value for the each color element and for each of all or a part of the plurality of blocks;    to judge, for each of all or a part of the plurality of blocks, whether the block being likely a part of a grey object or not;    to cumulate the predetermined values of the blocks judged as being likely a part of a gray object for the respective color elements, and;    to decide a first set of digital gains for adjusting white balance based on the cumulated values.    
   
   
       2 . A digital camera system according to  claim 1 , wherein the predetermined value is an average value of the color component in the block.  
   
   
       3 . A digital camera system according to  claim 1 , wherein the predetermined value is used for said judgment.  
   
   
       4 . A digital camera system according to  claim 1 , wherein the judgment is performed according to criteria decided based on one or more of histograms of the color elements, average values of the color elements, and a histogram of luminance of the image data.  
   
   
       5 . A digital camera system according to  claim 4 , wherein data of the block containing a saturated pixel is not involved in deciding the criteria.  
   
   
       6 . A digital camera system according to  claim 4 , wherein data of the block adjacent to the block containing a saturated pixel is not involved in deciding the criteria.  
   
   
       7 . A digital camera system according to  claim 4 , wherein the plurality of color elements comprise data representing red color, green color, and blue color, and the decision is contingent on one or more of B/G, R/G, min(R,B)/G, and max(R,B)/G satisfying the criteria 
 Where:    R represents an average value of the red data in the block to be judged.    G represents an average value of the green data in the block to be judged.    B represents an average value of the blue data in the block to be judged.    min(R,B)/G represents a value dividing a smaller one of the R and the B by the G.    max(R,B)/G represents a value dividing a larger one of the R and the B by the G.    
   
   
       8 . A digital camera system according to  claim 1 , wherein the block containing a saturated pixel is not involved in the cumulation.  
   
   
       9 . A digital camera system according to  claim 1 , wherein the block adjacent to the block containing a saturated pixel is not involved in the cumulation.  
   
   
       10 . A digital camera system according to  claim 1 , wherein the predetermined values of the block which is judged that its color is closer to white or gray than the other blocks are weighted at the cumulation.  
   
   
       11 . A digital camera system according to  claim 1 , wherein the system being arranged: 
 to define a plurality of intensity ranges;    to perform the gray judgment in the each intensity range; and    to perform the cumulation for the each intensity range.    
   
   
       12 . A digital camera system according to  claim 11 , wherein the intensity ranges are separated based on histograms of the color elements, and/or a histogram of luminance of the image data.  
   
   
       13 . A digital camera system according to  claim 11 , wherein the system being arranged to decide the first set of digital gains based on the cumulated values obtained from only a part of the plurality of the intensity ranges.  
   
   
       14 . A digital camera system according to  claim 11 , wherein the system being arranged to mix the cumulated values obtained from the different intensity ranges for the respective color elements; and to decide the first set of digital gains based on the mixed values.  
   
   
       15 . A digital camera system according to  claim 14 , wherein the system being arranged to perform the mixing by taking account of numbers of blocks whose color is judged as close to white or gray in each intensity range.  
   
   
       16 . A digital camera system according to  claim 14 , wherein the system being arranged to perform the mixing so that the cumulative value of the intensity range having higher luminance has a bigger influence on the mixed value.  
   
   
       17 . A digital camera system according to  claim 1 , wherein the system estimating a color tone of the image data and correcting the first set of digital gains based on the estimation.  
   
   
       18 . A digital camera system according to  claim 1 , wherein the system being arranged to calculate a second set of digital gains for adjusting white balance of the image data based on the Gray-world algorithm, and; to mix the first set of digital gains with the second set of digital gains to decide a final set of digital gains for adjusting white balance of the image data.  
   
   
       19 . A digital camera system according to  claim 12 , wherein the system being arranged to check a reliability of the final set of digital gains, and to calculate the first set of digital gains again by using the cumulated values deferent intensity ranges.  
   
   
       20 . An electric circuit for processing a frame of image data comprising a plurality of color elements, wherein the said circuit comprising: 
 a block extractor extracting a block of the image data, the block including a plurality of pixel data;    an average calculator calculating average values of each color component of the extracted block;    a judging unit judging whether the block being potentially white or not;    a cumulator cumulating the average values of a plurality of the extracted blocks whose color being judged as potentially white for the respective color elements, and;    a decision unit deciding a set of digital gains for adjusting white balance based on the cumulated values.    
   
   
       21 . An electric circuit according to  claim 20 , wherein the circuit comprising a plurality of intensity ranges, and wherein the judging unit is arranged to perform the judgment in the each intensity range, and the cumulator is arranged to perform the cumulation in the each intensity range.  
   
   
       22 . An electric circuit according to  claim 20 , wherein the circuit comprising a processor and a computer program, wherein the program instructs the processor to perform a part of functions of at least one of the block extractor, the judging unit, the cumulator, and the decision unit.  
   
   
       23 . A camera device comprising an electric circuit according to  claim 20.