Method of low-pass filtering and arrangement for performing said method
First Claim
Patent Images
1. An image processing method comprising:
- scanning, row by row, a two-dimensional picture comprising an array of pixels arranged in columns and rows to obtain a first sequence of signal values, successive signal values of each row of said first sequence corresponding to respective successive pixels of said picture which are arranged in a line direction;
storing said first sequence of signal values into a picture memory;
reading a second sequence of signal values picture memory column by column in a manner that successive signal values of each column correspond to respective successive pixels of said picture which are arranged in a direction perpendicular to the line direction;
generating a third sequence of filtered signal values by deriving each filtered signal value as a function of signal values comprised in a current kernel, said current kernel having a length consisting of L successive picture values of said second sequence and being shifted relative to said second sequence by one signal value position for each filtered signal value derived;
forming a difference between a value derived from a current kernel and a signal value of said second sequence at a position proximate to and not previously comprised in said current kernel;
incrementing the length of the current kernel to no more than a maximum length in case said difference is relatively small; and
decrementing the length of the current kernel to no less than a minimum length in case said difference is relatively large.
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Abstract
Signal smoothing can be improved without simultaneously obliterating the useful input signal edges by adaptively filtering the signal, in which the averaging interval is corresponding to the length of a kernel is incremented or decremented as a function of a difference between an output signal sample computed from the kernel and an output signal sample succeeding the kernel.
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Citations
4 Claims
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1. An image processing method comprising:
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scanning, row by row, a two-dimensional picture comprising an array of pixels arranged in columns and rows to obtain a first sequence of signal values, successive signal values of each row of said first sequence corresponding to respective successive pixels of said picture which are arranged in a line direction; storing said first sequence of signal values into a picture memory; reading a second sequence of signal values picture memory column by column in a manner that successive signal values of each column correspond to respective successive pixels of said picture which are arranged in a direction perpendicular to the line direction; generating a third sequence of filtered signal values by deriving each filtered signal value as a function of signal values comprised in a current kernel, said current kernel having a length consisting of L successive picture values of said second sequence and being shifted relative to said second sequence by one signal value position for each filtered signal value derived; forming a difference between a value derived from a current kernel and a signal value of said second sequence at a position proximate to and not previously comprised in said current kernel; incrementing the length of the current kernel to no more than a maximum length in case said difference is relatively small; and decrementing the length of the current kernel to no less than a minimum length in case said difference is relatively large. - View Dependent Claims (2, 4)
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3. An image processing apparatus comprising:
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a sensors for scanning, row by row, a two-dimensional picture comprising an array of pixels arranged in rows and columns, to obtain a first sequence of signal values, successive signal values of each row of said first sequence corresponding to respective successive pixels of said picture which are arranged in a line direction; a picture memory for storing said first sequence of signal and for supplying a second sequence of signal values read from said picture memory column by column in a manner that successive signal values of each column correspond to respective successive pixels of said picture which are arranged in a direction perpendicular to the line direction; and processing means for generating a third sequence of filtered signal values by deriving each filtered signal value as a function of signal values comprised in a current kernel, said current kernel having a length consisting of L successive picture values of said second sequence and being shifted relative to said second sequence by one signal value position for each filtered signal value derived, for forming a difference between a value derived from a current kernel and a signal value of said second sequence at a position proximate to and not previously comprised in said current kernel, for incrementing the length of the current kernel to no more than a maximum length in case said difference is relatively small, and for decrementing the length of the current kernel to no less than a minimum length in case said difference is relatively large.
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Specification