Image processing apparatus

Abstract

The invention concerns an image-processing apparatus, in which a high-frequency component signal of an original image-signal, representing a plurality of pixels, is added to either the original image-signal or a lowest frequency image-signal of the original image-signal, in order to generate a processed image-signal. The image-processing apparatus includes: a conversion-processing section to apply a conversion-processing to unsharp image-signals, generated from the original image-signal in respect to a plurality of frequency bands, so as to generate converted unsharp image-signals; a differential processing section to generate differential image-signals obtained from differences between the unsharp image-signals and the converted unsharp image-signals; and an addition-processing section to totally add the differential image-signals to generate the high-frequency component signal of the original image-signal.

1 . An image-processing apparatus, comprising: 
 an unsharp image-signal generating section to generate unsharp image-signals from an original image-signal in respect to a plurality of frequency-bands;    a differential processing section to generate differential image-signals from differences between the original image-signal and the unsharp image-signals, and to apply a conversion-processing to the differential image-signals so as to generate converted differential image-signals; and    an addition processing section to add said converted differential image-signals to the original image-signal or a lowest frequency image-signal to generate a processed image-signal;    wherein the conversion-processing varies depending on pixel values of the unsharp image-signals so as to suppress a conversion coefficient of the differential image-signals to the converted differential image-signals in sections where the pixel value of the unsharp image-signal represents lower density.    
   
   
       2 . The image-processing apparatus of  claim 1 , further comprising: 
 a compensation-signal calculating section to generate a compensation-signal which is derived from a low-frequency component signal obtained by subtracting a total sum of said converted differential image-signals from said original image-signal;    wherein said addition processing section adds said compensation-signal, instead of said converted differential image-signals, to said original image-signal or said lowest frequency image-signal to generate said processed image-signal.    
   
   
       3 . The image-processing apparatus of  claim 2 , 
 wherein said differential image-signals on which said conversion-processing depends are either anyone of image-signals utilized for obtaining said differential image-signals or both of them.    
   
   
       4 . The image-processing apparatus of  claim 2 , 
 wherein said conversion-processing applied to said differential image-signals varies depending on said differential image-signals.    
   
   
       5 . The image-processing apparatus of  claim 2 , 
 wherein said conversion-processing applied to said differential image-signals is a suppression-processing for suppressing an absolute pixel value at least at a part of image-signals.    
   
   
       6 . The image-processing apparatus of  claim 5 , 
 wherein the lower a frequency-band in which said differential image-signals reside is, the stronger a power of suppressing said absolute pixel value of said image-signals in said suppression-processing is.    
   
   
       7 . The image-processing apparatus of  claim 5 , 
 wherein the higher a frequency-band in which said differential image-signals reside is, the stronger a power of suppressing said absolute pixel value of said image-signals in said suppression-processing is.    
   
   
       8 . The image-processing apparatus of  claim 2 , 
 wherein a conversion-function is determined by designating a frequency characteristic, so as to realize a given frequency characteristic, and processing are conducted on the basis of said conversion-function.    
   
   
       9 . The image-processing apparatus of  claim 8 , 
 wherein said frequency characteristic can be changed depending on density.    
   
   
       10 . The image-processing apparatus of  claim 8 , 
 wherein said frequency characteristic can be changed depending on density of either said original image-signal or said unsharp image-signals for every differential image-signal.    
   
   
       11 . The image-processing apparatus of  claim 8 , 
 wherein sets of parameters for processing said frequency characteristic are provided in said image-processing apparatus, a kind of processing can be designated by selecting one set out of said sets of parameters.    
   
   
       12 . An image-processing apparatus, comprising: 
 a filter-processing section to apply a Gaussian weighting mask-processing to one pixel of an original image-signal, representing a plurality of pixels, with a mask so as to generate filtered original image-signals;    an unsharp image-signal generating section to generate unsharp image-signals from said filtered original image-signals;    a differential processing section to generate differential image-signals from differences between the original image-signal and the unsharp image-signals, or from differences between the unsharp image-signals themselves; and    an addition processing section to add the differential image-signals to the original image-signal or a lowest frequency image-signal with respect to the original image-signal in order to generate a processed image-signal;    wherein a frequency characteristic of the processed image-signal can be varied by changing a frequency characteristic of the mask employed for the mask-processing, and    wherein the mask-processing is repetitions of filter-processing with a simple average filter.    
   
   
       13 . An image-processing apparatus, comprising: 
 an unsharp image-signal generating section applying a Gaussian weighting mask-processing to one pixel and generating a plurality of unsharp image-signals from a original image-signal, representing a plurality of pixels;    a differential processing section to generate differential image-signals from the unsharp image-signals or the original image-signal; and    an addition processing section to add the differential image-signals to the original image-signal or a lowest frequency image-signal with respect to the original image-signal in order to generate a processed image-signal;    wherein repetitions of filter-processing with a simple average filter are conducted for generating each of the unsharp image-signals.    
   
   
       14 . The image-processing apparatus of  claim 13 , further comprising: 
 a compensation-signal calculating section to generate a compensation-signal which is derived from a low-frequency component signal obtained by subtracting a total sum of said differential image-signals from said original image-signal;    wherein said addition processing section adds said compensation-signal, instead of said differential image-signals, to said original image-signal or said lowest frequency image-signal to generate said processed image-signal.    
   
   
       15 . The image-processing apparatus of  claim 13 , 
 wherein a mask employed for said repetitions of filter-processing is a simple average of 2 pixels×2 pixels.    
   
   
       16 . The image-processing apparatus of  claim 13 , 
 wherein a mask-processing varies depending on said unsharp image-signals.    
   
   
       17 . The image-processing apparatus of  claim 13 , 
 wherein a mask-processing varies depending on said original image-signal.    
   
   
       18 . The image-processing apparatus of  claim 13 , 
 wherein a mask-processing varies depending on a frequency characteristic of said original image-signal.    
   
   
       19 . The image-processing apparatus of  claim 15 , 
 wherein a number of repetitions of said single average of 2 pixels×2 pixels is not less than 16.    
   
   
       20 . The image-processing apparatus of  claim 15 , 
 wherein a number of repetitions of said single average of 2 pixels×2 pixels not less than 8.