JP2587555B2 - Two-dimensional sequential filter circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-dimensional image composed of a large number of pixels arranged in a row direction and a column direction, respectively, in an area composed of a plurality of pixels arranged in a row direction and a column direction. The operation of selecting pixel data in a predetermined order from the maximum value side or the minimum value side when arranging the respective pixel data corresponding to the respective pixels in the order of the pixel values is performed by sequentially moving the above-described area. The present invention relates to a two-dimensional sequential filter circuit performed over the entire area.

[0002]

2. Description of the Related Art For example, a so-called median filter for picking up pixel data having a median value from a plurality of pixel data in a predetermined area on a two-dimensional image is used. In the field of image processing, two-dimensional ordered filters that need to be arranged in a matrix are frequently used, and various algorithms for realizing two-dimensional ordered filters suitable for hardware have been proposed.

FIG. 3 shows an example of an algorithm for realizing a two-dimensional ordered filter, that is, a so-called odd-even filter.
It is explanatory drawing of a sort (Odd-Even-Sort) ("Design and
Implementation of a General-Purpose Median FilterU
nit in CMOS VLSI '' MUSTAFA KARAMAN, LEVENT ONURAL,
ABDULLAH ATALAR, GOURNAL OF SOLID-STATECIRCUITS,
VOL.25, NO.2 See APRIL 1990, P505-P513). Here, a case where nine data are arranged in the order of their values will be described.

A large number of blocks 10 shown in FIG. 1 compare two input data values, output large data from a left output terminal and output small data from a right output terminal. For example, a circuit block including a combination of a comparator and a multiplexer.
For example, a median filter can be realized by selecting the fifth data from the maximum value side by employing this algorithm.

[0005]

However, when a two-dimensional order filter using the above algorithm is implemented in hardware, it is necessary to rearrange nine data in order of their values.
It is necessary to provide as many as 36 circuits corresponding to each block 10 shown in FIG.

The following algorithm is known as an algorithm for realizing a median filter having a small circuit scale (see Japanese Patent Application Laid-Open No. 1-116887). FIG. 4 is an explanatory diagram of an algorithm for realizing the median filter. In this figure, it is assumed that each cell shown in the figure corresponds to each pixel, and the number described therein is the pixel value of the pixel data of the pixel.

[0007] As shown in FIG.
The pixels are divided for each column as shown in FIG. 4B, and the respective median values (numbers with circles in FIG. 3B) of the three pixel data in each column are detected. Next, the median is further detected from the three medians thus detected. In this case, two comparators are required to detect each median of the three pixel data in each column, and two comparators are required to detect the median from among the three medians. And therefore a total of 8
It is possible to detect the median value of nine pixel data simply by providing the comparators.

However, this algorithm may not be able to detect the correct median value.
In the example shown in FIG. 7, the result is that “4” is detected even though the true median is “5”. The present invention has been made in view of the above circumstances, and has as its object to provide a two-dimensional sequential filter circuit which can be realized with a small circuit scale and can correctly detect desired data.

[0009]

To achieve the above object, a first two-dimensional sequential filter circuit according to the present invention is a two-dimensional sequential filter circuit comprising: a plurality of pixels arranged in a row direction and a column direction; The maximum value is obtained by arranging pixel data corresponding to each pixel in an area composed of N1 × N2 pixels arranged in N1 rows in the row direction and N2 pixels in the column direction from the maximum value side in pixel value order. A two-dimensional sequential filter circuit that performs an operation of selecting pixel data having a predetermined order over the entire area on a two-dimensional image while sequentially moving the area. A one-dimensional sorter circuit for sequentially performing an operation of rearranging the pixel data corresponding to each pixel in the partial region composed of N2 pixels arranged in the column direction in the pixel direction in the order of the pixel value for each partial region (2) One-dimensional sorter circuit N2 pixel data corresponding to each of the partial areas arranged in order of pixel value is stored in order of pixel value.
(3) The maximum value for detecting the maximum value among the N1 maximum values by comparing the maximum values of the pixel data stored in the N1 latch circuits for each of the latch circuits. Value detection circuit (4) N2 stored in the latch circuit storing the pixel data having the maximum value detected by the maximum value detection circuit
The pixel data having the minimum value among the pixel data having the minimum value in the pixel data stored in the latch circuit by shifting the pixel data one by one to the pixel data side having the large pixel value. Alternatively, N1 shift circuits provided to accompany each of the N1 latch circuits for storing data having a value distinguishable from pixel data. (5) The maximum value detection circuit detects a maximum value and The shift circuit is provided with each element of a counter for counting the number of times of a routine for shifting pixel data.

A second two-dimensional sequential filter circuit according to the present invention comprises N1 pixels in a row direction and N2 pixels in a column direction on a two-dimensional image composed of a large number of pixels arranged in a row direction and a column direction. An operation of selecting pixel data in a predetermined order from the minimum value when arranging the pixel data corresponding to each pixel in the region composed of N1 × N2 pixels arranged in order from the minimum value side In a two-dimensional sequential filter circuit that sequentially moves the above-mentioned area over the entire area on the two-dimensional image. (6) N2 pixels in the above-mentioned area, one in the row direction and N2 in the column direction A one-dimensional sorter circuit for sequentially performing an operation of rearranging each pixel data corresponding to each pixel in the partial region in the order of the pixel value for each partial region. (7) The one-dimensional sorter circuit arranged in the order of the pixel values by the one-dimensional sorter circuit. Each part N2 pixel data corresponding to the respective areas are stored in the order of pixel values.
(8) The minimum value for detecting the minimum value among the N1 minimum values by comparing the minimum values of the pixel data stored in the N1 latch circuits for each of the latch circuits. Value detection circuit (9) N2 stored in the latch circuit storing the pixel data having the minimum value detected by the minimum value detection circuit
The pixel data having the maximum value among the pixel data having the maximum value in the pixel data stored in the latch circuit by shifting the pixel data one by one to the pixel data side having the small pixel value. Alternatively, N1 shift circuits provided to accompany each of the N1 latch circuits for storing data having a value distinguishable from pixel data. (10) The minimum value detection circuit detects a minimum value, The shift circuit is provided with each element of a counter for counting the number of times of a routine for shifting pixel data.

Here, the above "row direction" and "column direction"
Is simply a matter of how the images are arranged, and of course any direction may be considered as the row direction or the column direction. Further, the shift circuit physically and physically stores the data stored in the latch circuit.
The circuit does not need to be electrically shifted, and may be, for example, a circuit for instructing a read pointer or a write pointer of a memory circuit. When the data stored in the latch circuit is actually shifted by the shift circuit and the first data is lost by this shift, the data stored in the latch circuit output from the one-dimensional sorter circuit is first stored. It is preferable to store the pixel data to be processed.

[0012]

In the two-dimensional sequential filter of the present invention, the pixel data is rearranged in the order of the pixel value by the one-dimensional sorter circuit ((1), (6)) and latched ((2), (7)). The maximum or minimum value is detected by a maximum value detection circuit ((3)) or a minimum value detection circuit ((7)), and the maximum or minimum value is counted by a counter ((5), (5)).
(10)), the shift circuit ((4), (9)) pushes out the data a required number of times while counting. For example, desired data can be correctly detected.

Incidentally, as in the above-mentioned conventional example, N1 =
3, N2 = 3, that is, when the median value (pixel data having the fifth value from the maximum value or the minimum value) is extracted from the nine pixels, the number of times of judging the size of the two data is: Two comparisons are performed by the one-dimensional comparator twice and two times by the maximum value detection circuit or two times by the minimum value detection circuit, that is, a total of 12 comparisons, and only 1/3 of 36 times of the odd even sort shown in FIG. It will be. In addition, an accurate median can be obtained as compared with the algorithm described with reference to FIG.

[0014]

Embodiments of the present invention will be described below. FIG. 1 is a diagram showing an algorithm of a circuit configured to select a median from 3 × 3 = 9 pixels, which is one embodiment of the first two-dimensional sequential filter circuit of the present invention.
FIG. 2 is a schematic diagram showing movement of data in FIG. 1.

On a two-dimensional image composed of a large number of pixels P arranged in a row direction A and a column direction B, an area 20 composed of a total of 9 pixels arranged three in the row direction and three in the column direction It is assumed that pixel data having pixel values as shown in FIG. Here, pixel data having a median value is selected from these nine pixel data.

The data is input to the one-dimensional sorter 11 two times before, and one line is arranged in the row direction and three lines are arranged in the column direction.
The pixel data of the partial area 20a composed of three pixels having each pixel value of “1” is determined as to the magnitude of the pixel value of these pixel data, and the maximum value “25” is sequentially stored in the latch circuit 12 from the bottom of the figure. , The median value “6” and the minimum value “1” are latched. Similarly, the pixel data of the partial area 20b consisting of three pixels having the respective pixel values of '31', '5', and '7', which was input to the one-dimensional sorter 11 last time, is also stored in the latch circuit 13 Latched to.

In this state, the data of the partial area 20c composed of three pixels having the pixel values of "2", "3", and "9" is similarly input to the one-dimensional sorter, Is determined and latched by the latch circuit 14. When the pixel data of each partial area 20a, 20b, 20c is latched by the latch circuits 12, 13, 14 in this manner, the maximum values' 9 ',' 31 ',' The magnitude of 25 'is compared and determined.
Here, since “31” latched by the latch circuit 13 is the maximum, the latch circuit 1 is switched as shown in FIG.
3, the pixel data having the pixel value 31 is pushed out, and the minimum value “0” of the numerical value handled by the two-dimensional sequential filter circuit is placed at the top of the latch circuit 13 in FIG.
Is latched. The detection of the maximum value by the maximum value detection circuit 15 and the movement of data by the latch circuit 13 cause the counter 16 to count up by one.

Next, the maximum value detection circuit 15 compares the maximum values of the latch circuits 12, 13, and 14, that is, "9", "7", and "25". When "25" is detected, the data latched by the latch circuit 12 is moved as shown in FIG. 2B, and the counter 16 counts up to "2". The above operation is repeated, and the pixel data '6' pushed out when the counter 16 becomes 5 becomes the median value corresponding to this area 20.

Next, in order to detect the median value of the area 21, three pixel data of the partial area 21c are input to the one-dimensional sorter 11. For example, each partial region belongs to three regions so that the partial region 20c belongs to three regions 20, 21, 22. Therefore, data passed through the one-dimensional sorter 11 is stored so as not to be erased by the above data movement. Then, it can be used to detect the median of the three regions. Therefore, the number of comparisons of the two data for detecting the median value in one area is two times in the one-dimensional sorter and two times in the maximum value detection circuit 15 × 5 times in total, ie, 12 times in total. The value can be detected accurately.

Although the above embodiment is an embodiment of the first two-dimensional sequential filter circuit of the present invention, three latch circuits 12, 13, and 14 are provided with pixel data having a small value on the lower side of FIG. , And a minimum value detection circuit is provided in place of the maximum value detection circuit 15.
By configuring so that the maximum value or the like that can be handled by this two-dimensional sequential filter circuit is input instead of the value “0” input from the top of the figure in FIGS. One embodiment of the dimensional order filter circuit is configured. Since the operation in this embodiment is described in substantially the same manner as described above, its illustration and description are omitted here.

Although the above embodiment is a circuit for detecting the median value in a region consisting of a total of 9 pixels in which 3 pixels are arranged in each of the row direction and the column direction, the present invention provides an arbitrary number N in the row direction.
This can be adopted when detecting pixel data in an arbitrary order from the maximum value or the minimum value in an N1 × N2 pixel area in which an arbitrary number N2 of pixels are arranged in the column direction.

[0022]

As described above, in the two-dimensional sequential filter circuit of the present invention, the one-dimensional sorter circuit arranges the pixel data in each partial area in the order of their pixel values, and sets the maximum value in a plurality of partial areas. Alternatively, since the minimum values are compared a predetermined number of times, desired pixel data can be accurately extracted with a small-scale circuit configuration.

[Brief description of the drawings]

FIG. 1 is an embodiment of a first two-dimensional sequential filter circuit of the present invention.

FIG. 2 is a schematic diagram showing movement of data in FIG.

FIG. 3 is an explanatory diagram of a so-called odd-even sort, which is an example of an algorithm for realizing a two-dimensional ordered filter.

FIG. 4 is an explanatory diagram of an algorithm for realizing a conventional median filter.

[Explanation of symbols]

 11 One-dimensional sorter 12, 13, 14 Latch circuit 15 Maximum value detection circuit 16 Counter

Claims (2)

(57) [Claims] 1. A two-dimensional image composed of a large number of pixels arranged in large numbers in a row direction and a column direction, respectively.
When each pixel data corresponding to each pixel in an area composed of N1 × N2 pixels arranged in N2 rows in the column direction is arranged in order of pixel value from the maximum value side, a predetermined order from the maximum value A two-dimensional sequential filter circuit for performing an operation of selecting pixel data in the area over the entire area on the two-dimensional image while sequentially moving the area, wherein: one in the row direction and one in the column direction in the area. N2 lined up
A one-dimensional sorter circuit that sequentially performs an operation of rearranging each pixel data corresponding to each pixel in a partial region composed of a plurality of pixels in the order of pixel values for each partial region; N1 latch circuits provided for each of the partial areas for storing N2 pixel data corresponding to the respective partial areas in the order of pixel values, and pixel data stored in the N1 latch circuits. A maximum value detection circuit for comparing the maximum values among the latch circuits to detect the maximum value among the N1 maximum values; and a pixel having the maximum value detected by the maximum value detection circuit. The N2 pixel data stored in the latch circuit in which the data is stored is shifted one by one to the pixel data side having the larger pixel value, and the pixel having the minimum value among the pixel data stored in the latch circuit is shifted. Data An N1 shift circuit provided in association with each of the N1 latch circuits, for storing data having a minimum value in the pixel data or data having a value distinguishable from the pixel data in the stage; 2. A two-dimensional sequential filter circuit comprising: a counter for detecting a maximum value in a value detection circuit and counting the number of routines for shifting pixel data in the shift circuit. 2. A two-dimensional image composed of a large number of pixels lined up in a row direction and a column direction, respectively.
When each pixel data corresponding to each pixel in an area composed of N1 × N2 pixels arranged in N2 rows in the column direction is arranged in order of pixel value from the minimum value side, a predetermined order from the minimum value is obtained. A two-dimensional sequential filter circuit for performing an operation of selecting pixel data in the area over the entire area on the two-dimensional image while sequentially moving the area, wherein: one in the row direction and one in the column direction in the area. N2 lined up
A one-dimensional sorter circuit that sequentially performs an operation of rearranging each pixel data corresponding to each pixel in a partial region composed of a plurality of pixels in the order of pixel values for each partial region; N1 latch circuits provided for each of the partial areas for storing N2 pixel data corresponding to the respective partial areas in the order of pixel values, and pixel data stored in the N1 latch circuits. A minimum value detection circuit for comparing minimum values among the latch circuits to detect a minimum value among the N1 minimum values, and a pixel having a minimum value detected by the minimum value detection circuit. The N2 pixel data stored in the latch circuit in which the data is stored is shifted one by one to the pixel data side having the smaller pixel value, and the pixel having the maximum value in the pixel data stored in the latch circuit is shifted. Data An N1 shift circuit provided in association with each of the N1 latch circuits, for storing data having a maximum value in pixel data or data having a value distinguishable from pixel data in a stage; A two-dimensional sequential filter circuit, comprising: a counter for detecting a minimum value in a value detection circuit and counting the number of routines for shifting pixel data in the shift circuit.