JPS6371784A - Binarizing device for picture signal - Google Patents

Abstract

PURPOSE:To effectively binarize both two and multiple tone wedge parts when the two and multiple tone wedge parts exist in the same original, by outputting binarized data in accordance with the density of a point to be binarized and the weighted mean density of the surroundings of the point. CONSTITUTION:In the case of a two tone wedge picture, such as a character, etc., with which the density of a point to be binarized and the weighted mean density of the surroundings of the point are largely different from each other, '1' or '0' is forcibly outputted to a terminal 13. Moreover, when the density value of the point to be binarized is smaller than the sum of the weighted mean density value of the surroundings and a prescribed value, but larger than a value obtained by subtracting the prescribed value from the weighted mean density value, the output of a comparator 7 becomes '0' and that of another comparator 8 goes to '1'. In case of a multiple tone wedge picture, such as a photograph, etc., with which the density of a point to be binary coded is close to the weighted mean density value of the surroundings of the point, binarized data are outputted in accordance with the weighted mean density value of the surroundings.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image signal binarization device that binarizes an analog image signal.

<Prior Art> A dither method is a method for converting a multi-tone original such as a photograph into an image signal. Further, a two-tone original such as text is converted into a two-tone image signal. However, in actual documents, there may be a mixture of some documents, such as photographs, which are better converted into multi-tone image signals, and some documents, such as letters, which are better converted into two-tone image signals. In this case, when the dither method is used, the characters may become unreadable or difficult to read, and when converted to a two-tone image signal, the multi-tone portions are lost.

<Object of the Invention> The present invention has been made in view of the above-mentioned circumstances. The purpose is to provide a

<Embodiment> Hereinafter, one embodiment of the image signal binarization device of the present invention will be described based on the drawings.

The AD converter 1 converts an analog video signal of a certain range of an original image into 8-bit digital data. The greater the value of the converted digital data, the greater the density of the original image. Memory 2 is AD converter 1
Store digital data from. The D-type flip-flop 3 latches digital data at points to be binarized in the original image.

The weighted average density calculating circuit 4 calculates the weighted average value of the density of points within this range from digital data of 15×15 points centered on the point to be binarized.

When the weighted average density value is given as address data from the weighted average density calculation circuit 4, the addition FROM 5 outputs a value obtained by adding a predetermined value to this weighted average value. When the weighted average density value is given as address data from the weighted average density calculation circuit 4, the subtraction FROM 6 outputs a value obtained by subtracting a predetermined value from this weighted average value.

The comparator 7 compares the data held by the D-type flip-flop 3 with the data output from the addition FROM 5, and the data of the D-type flip-flop 3 is compared with the data held by the addition FROM 5.
If the data is greater than the data of , it outputs "1".
It compares the data output by OM6, and if the data of D-type flip-flop 3 is smaller than the data of FROM 6 for subtraction, it outputs "0", and the data of D-type flip-flop 3 is larger than the data of FROM 6 for subtraction. If so, @1''' is output.

FROM9 for dithering is 2 of the given address data.
The bits are used to select the dither type, and the remaining 6 bits are used to select the dither type.
One point of the ×8 dither pattern is selected. The comparator 10 compares the output data of the dither PROM 9 and the weighted average value of the density from the weighted average density calculation circuit 4,
The weighted average concentration is binarized using the dither method and the data is output.

The output of the comparator 7 is given to an OR circuit 11.

The outputs of comparator 8 and comparator 10 are applied to an AND circuit 12, and the output of this AND circuit 12 is applied to an OR circuit 11. The output of the OR circuit 11 is output to a terminal 13 of this image signal binarization device.

Now, if the concentration value of the point to be binarized is larger than the value obtained by adding a predetermined value to the weighted average value of the surrounding concentration, the comparator 7
The output of the terminal 13 becomes "1", and the output of the terminal 13 becomes "11".In addition, if the density value of the point to be binarized is smaller than the value obtained by subtracting a predetermined value from the weighted average value of the surrounding density, the output of the comparator 7 becomes "1". ．．
8 becomes "0" and terminal 13 becomes "0". In other words, when the density of the point to be binarized and the weighted average density of the surrounding area are significantly different from each other, the output of terminal 13 becomes "0". 1
3 is forcibly output as 1" or "01.

Further, if the concentration value of the point to be binarized is smaller than the value obtained by adding a predetermined value to the weighted average value of the surrounding concentration, and larger than the value obtained by subtracting the predetermined value from the weighted average value of the surrounding concentration, The output of comparator 7 becomes "0" and the output of comparator 8 becomes "1".

Then, the data obtained by converting the weighted average concentration output from the comparator 10 into binary data using the dither method is sent to the AND circuit 12.
is output to the terminal 13 via the OR circuit 11. In other words, when the density of a point to be binarized is close to the weighted average density of the surrounding area, such as a multi-tone image such as a photograph, the binarized data is output according to the weighted average value of the surrounding density. Ru.

<Effects of the Invention> As explained above, in the present invention, when the density of a point to be binarized and the weighted average density of the surrounding area are significantly different, "1" is forcibly set depending on the magnitude relationship with the surrounding density. or “O
When the density of the point to be binarized is close to the weighted average density of the surrounding area, the binarized data corresponding to the weighted average density is output. When a two-tone part such as text and a multi-tone part such as a photograph coexist, both the two-tone part and the multi-tone part can be effectively binarized. Further, since a weighted average value is used when dithering, moiré does not occur even if the original image is a halftone image. Further, by setting the weighting when calculating the weighted average value to an appropriate value according to the input image quality, it is possible to obtain an appropriate output image according to the input image quality.

[Brief explanation of the drawing]

The drawing is a block diagram showing the basic configuration of an embodiment of the present invention. 1...AD converter 2...Memory 3--D-type flimback float 4-Loaded average concentration calculation circuit 5--FROM for addition 6--FROM for subtraction 7.8.10--Comparator 9 ... Dither PROM 11 ... OR circuit 12 ... AND circuit

Claims (1)

[Claims] In a device that binarizes an analog image signal, two
a calculation means for calculating a weighted average value of the concentration of points in a predetermined range in the vicinity of the point to be digitized; a first binarized data generation means for generating binarized data according to the magnitude relationship between the density value of the point to be binarized and the weighted average value; and the density value of the point to be binarized and the weighted average value. An image signal binarization device comprising second binarization data generation means for generating binarization data according to the weighted average value when the difference from the average value is less than or equal to a predetermined value. .