JPH05303639A - Edge extraction circuit from digital video signal - Google Patents

Abstract

PURPOSE:To extract edge information in digital picture by means of simple hardware or processing. CONSTITUTION:An input digital video signal is divided into smaller blocks in a blocking circuit 2. A maximum detection circuit 3 and a minimum detection circuit 4 detect the maximum and minimum values of each block and the dynamic range DR being the difference is obtained from a subtraction circuit 5. The dynamic range DR is supplied to a comparison circuit 6, and the value of the entire picture element is taken as '1' when DR>Th, and is taken as '0' when DR<=Th.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge extraction circuit for extracting edge information from a digital video signal.

[0002]

2. Description of the Related Art Extracting edge information from a digital video signal has various fields of use in digital image processing such as position detection of a chip component during automatic mounting in a manufacturing process. Conventionally, a differential filter or a Laplacian filter is used, and a place where the level change of the digital video signal is drastic is detected as an edge.

[0003]

However, when the above-mentioned filter is constituted by a digital circuit, a digital multiplier is generally required, and there is a problem that the scale of hardware becomes large. Further, there is a problem that the edge extraction cannot be performed when the level change is not relatively large.

Therefore, an object of the present invention is to provide an edge extraction circuit which can be realized by a simple hardware or software process which does not use a multiplier, and which can extract edges even when the level change is not large. is there.

[0005]

According to the present invention, there is provided means for subdividing an input digital video signal into block unit data consisting of a plurality of pixel data, and detecting maximum and minimum values of the plurality of pixel data for each block. , The difference between the maximum value and the minimum value is compared with a threshold value, and all pixel data of blocks whose difference is greater than the threshold value is set to one of “0” or “1”, and the difference is greater than the threshold value. It is an edge extraction circuit from a digital video signal, which comprises means for setting all pixel data of a small block to the other value of "0" or "1".

[0006]

The brightness difference exists in the block containing the edge information. When the brightness difference is larger than the threshold value, it is determined that the edge information exists.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 is an input terminal to which a digital video signal is supplied. This digital video signal is converted from the raster scanning order to the block order by the block forming circuit 2. As a block,
As shown in FIG. 2A, the size is (n pixels × m lines). The block size is appropriately selected in consideration of the usage field of the extracted edge information. The blocking circuit 2 includes an m line memory.

A maximum value detection circuit 3 and a minimum value detection circuit 4 are connected to the blocking circuit 2. The maximum value detection circuit 3 detects the maximum value MAX for each block, and the minimum value detection circuit 4 detects the minimum value MIN for each block. The minimum value MIN is subtracted from the maximum value MAX by the subtraction circuit 5, and the subtraction circuit 5 obtains the dynamic range DR of the block. This dynamic range DR is supplied to the comparison circuit 6 and compared with a certain threshold Th.

In the comparison circuit 6, an output of "1" is generated when DR> Th, and an output of "0" is generated when DR≤Th. The output signal of the comparison circuit 6 is obtained by replacing the values of all the pixels in the block with "1" or "0". That is, if the dynamic range DR of the block is larger than the threshold Th, it is determined that the block has edge information, and the values of all pixels in the block are set to "1". If not, the values of all pixels in the block are set to "0".

The output signal of the comparison circuit 6 is supplied to the block decomposition circuit 7 and converted from the block order to the raster scan order. Therefore, output data having a value of "0" or "1" is obtained at the output terminal 8.

Considering an input image in which a triangular object 11 exists in one screen as shown in FIG. 2A, all pixels of the block including the edge thereof are set to "1" as described above. Therefore, as shown in FIG. 2B, an output image in which the block 12 corresponding to the edge is set to the white level and the other blocks are set to the black level is obtained.

Contrary to this embodiment, the pixel value of the block including the edge may be "0" and the pixel value of the other blocks may be "1". Further, when the output image is displayed, the "0" and "1" pixels may be converted into distinguishable levels or colors other than the black and white levels.
Furthermore, even in computer software processing,
Since the processing can be performed at extremely high speed, it can be realized in real time even in a general-purpose image processing apparatus using a computer.

[0013]

The present invention has an advantage that the scale of hardware is small because a digital multiplier is not required unlike a digital differential filter. Further, it can be realized with a small number of steps of software. Further, it is possible to extract an edge having a small difference in brightness.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining one embodiment of the present invention.

[Explanation of symbols]

 3 Maximum value detection circuit 4 Minimum value detection circuit 6 Comparison circuit

Claims (1)

[Claims] 1. A unit for subdividing an input digital video signal into block-unit data consisting of a plurality of pixel data and detecting the maximum and minimum values of the plurality of pixel data for each block, and the maximum and minimum values. The difference between the values is compared with a threshold value, and all the pixel data of the block in which the difference is larger than the threshold value are set to one of "0" or "1", and the difference is set to the threshold value. An edge extraction circuit from a digital video signal, which comprises means for setting all the pixel data of the smaller block to the other value of "0" or "1".