JPH01117568A - Binary picture magnification and reduction device - Google Patents

Abstract

PURPOSE:To obtain an excellent transformed picture with less missing of black information independently of the quantity of the transforming rate by applying transformation by the projection method when the transforming magnification is large and applying the transforming by the logical OR method when the transforming magnification is small. CONSTITUTION:In giving an original picture 11 to a coordinate transforming section 1, a coordinate transforming section 1 outputs a color signal 12 of four points original picture elements a, b, c, d around the transforming picture element (x) and a coordinate 13 of the transforming picture element (x) in response to a magnification signal 17 outputted by a control section 5. An OR arithmetic section 2 outputs a chrominance signal 14 of the transforming picture element (x) based on the OR method from the chrominance signal 12 of the original picture elements a, b, c, d. A projection method arithmetic section 3 uses the chrominance signal 12 of the original picture elements a, b, c, d and the coordinate 13 of the transforming picture element (x) to output a chrominance signal 15 of the transforming picture element (x) based on the projection method. The control section 5 compares the magnification T with a threshold level T and selects the output of the selector 4 from the result.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is applied to a facsimile machine. INDUSTRIAL APPLICATION This invention is utilized for the enlargement/reduction circuit of a binary image. In particular, it relates to an enlargement/reduction circuit using coordinate transformation.

〔overview〕

The present invention is a means for enlarging/reducing a two-dimensional binary image, in which the conversion is performed using a projection method when the conversion magnification is large, and the conversion is performed using the logical sum method when the conversion magnification is small, thereby preventing the disappearance of black pixels. This makes it possible to prevent this problem and obtain a good converted image.

[Conventional technology]

Conventional techniques for enlarging/reducing binary images by coordinate transformation include the logical sum method and the projection method. FIG. 2 is an explanatory diagram of coordinate transformation. The circles are the matrix of the centers of the pixels of the original image, and the distance between adjacent pixels is l. Here, the magnification is 0.
When performing the reduction by 75, the new matrix of converted pixels is represented by triangles, and the grid spacing is 1.33.

Now, in the logical sum method, the black and white of the new converted pixel X is the surrounding 4
It is determined by the black and white colors of the original pixels a, bSc, and d.

That is, if even one of the original pixels aSbSCSd is black, the new converted pixel X is determined to be black. FIG. 3 is an explanatory diagram of the projection method. Straight lines A and B are original pixels a, b, c,
This is a crosshair that divides the rectangle abcd formed by d into four equal parts. That is, straight line A equally divides line segment ad and line segment bc, and straight line B equally divides line segment ab and line segment cd.

The rectangle is a projection area of the converted pixel X to the original coordinates, and the converted pixel X is the center of the rectangle. Conversion magnification is 0.75
(--), the length of one side of the rectangle is its reciprocal, ie, 1.33 (=-). Area a', b', α
', d' are quadrilaterals divided by straight lines A and B. Here, α, β, and T1δ are each original pixel a
, b, cSd pixel density (black = 1, white = 0), and α'
, β', γ', and δ' are the areas of regions a', b', α', and d', respectively, then the converted density X of the converted pixel X is expressed by the following equation.

However, F: magnification, 0≦X≦1.

When this conversion density X exceeds a predetermined threshold level TH (0<TH<1 person), the conversion pixel X is determined to be black, and when it is below, it is determined to be white.

[Problem that the invention seeks to solve]

However, although the disjunction method rarely loses black pixels as information during conversion, it has the disadvantage that the image as a whole becomes blurred, whereas the projection method is close to optical conversion and is good overall. Although a converted image can be obtained, there is a drawback that information is easily lost due to the disappearance of black pixels when the conversion magnification is small, that is, during reduction.

SUMMARY OF THE INVENTION The present invention aims to eliminate such drawbacks and to provide a binary image enlarging/reducing device that can prevent black pixels from disappearing and at the same time provide a good converted image.

[Means for solving problems]

In the present invention, pixels located at the lattice points of a lattice whose lattice spacing is a value proportional to the reciprocal of the enlargement or reduction magnification for a two-dimensional binary original image are converted pixels, and this converted pixel is included in the area and the magnification is The density of the pixel of the original image located at the four grid points weighted by the area ratio of the four regions obtained by dividing the rectangle formed by the four grid points of the grid with the grid spacing set to "1" by cross lines. In a binary image enlarging/reducing device having a first means for determining the black and white of this converted pixel by determining the black and white of this converted pixel by determining the average value of the values as the density value of this converted pixel and comparing this density value with a threshold value, a magnification of "1" is used. a second means for determining the blackness and whiteness of a converted pixel located within an area defined by the four grid points according to the blackness and whiteness of pixels of the original image located at four grid points of a grid having a grid interval, and the first means described above; or the output signal of the second means according to the enlargement or reduction magnification.

[Effect]

When the magnification exceeds a certain value, the black and white of the converted pixel is determined by calculations using the projection method, while when it is below, the black and white of the converted pixel is determined by calculations using the logical sum method. This prevents the disappearance of black pixels during reduction by the projection method, and provides a good converted image by the projection method during enlargement.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. 1st
The figure is a block configuration diagram showing the configuration of this embodiment.

In this embodiment, as shown in FIG. 1, pixels located at grid points of a grid whose grid spacing is a value proportional to the reciprocal of the enlargement or reduction magnification for a two-dimensional binary original image are used as conversion pixels. Four lattice points weighted by the area ratio of four regions obtained by dividing a rectangle formed by four lattice points of a lattice with a lattice interval with a magnification of "1" into four regions with cross lines, including the converted pixel in that region. The projection method calculation unit 3 is a first means for determining the black and white of this converted pixel by determining the average value of the density values of pixels of the original image located at , as the density value of this converted pixel, and comparing this density value with a threshold value. and a second method that determines the blackness and whiteness of the converted pixels located within the area defined by these four lattice points according to the blackness and whiteness of the pixels of the original image located at the four lattice points of the lattice whose lattice spacing is a magnification of "1". It is provided with a logical sum calculation unit 2 which is a means, and a selector 4 which selects either the output signal of the first means or the output signal of the second means according to the enlargement or reduction magnification.

Now, the original image 11 is input to the coordinate transformation section 1.

The coordinate conversion unit 1 outputs the coordinates 13 of the converted pixel X and the color signals 12 of four original pixels aSb, 'c, and d around the converted pixel X in accordance with the magnification signal 17 outputted by the control unit 5.

The logical sum calculation unit 2 outputs the color signal 14 of the converted pixel X based on the logical sum method from the color signals 12 of the original pixels a, b, c, and d. The projection method calculation unit 3 calculates the original pixel aSbSc.

A color signal 15 of the converted pixel X is output based on the projection method using the color signal 12 of d and the coordinates 13 of the converted pixel X. The control unit 5 compares the conversion magnification r and the threshold level T, and selects the output of the selector 4 based on the comparison result.

That is, when r≧T, the selector 4 outputs the signal line 15, and when r<T, the selector 4 outputs the signal line 14.

〔Effect of the invention〕

As explained above, in the present invention, when the conversion magnification is large, the conversion is performed using the projection method (in the direction of enlargement), and when the conversion magnification is small, the conversion is performed using the disjunctive method (in the direction of reduction). This has the effect of obtaining a converted image with good quality and less loss of black information.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing the configuration of an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the operation of the logical sum method. FIG. 3 is an explanatory diagram showing the operation of the projection method. 1... Coordinate transformation section, 2... Logical OR operation section, 3...
Projection calculation unit, 4...Selector, 5...Control unit. Patent applicant: NEC Corporation 1. -1- Agent Patent Attorney Nao Ide Takami Noodles Example 1st φ 6 0i 0i. 1---Song dynasty------------One hole------
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Claims (1)

[Claims] (1) A pixel located at a lattice point of a lattice whose lattice spacing is a value proportional to the reciprocal of the enlargement or reduction magnification for a two-dimensional binary original image is a converted pixel, and this converted pixel is included in the area and the magnification is The density value of the pixel of the original image located at the four grid points weighted by the area ratio of the four regions obtained by dividing the rectangle formed by the four grid points of the grid with a grid interval of "1" by cross lines. In a binary image enlarging/reducing device comprising a first means (3) for determining the black and white of this converted pixel by determining the black and white of this converted pixel by determining the average value of this converted pixel as the density value and comparing this density value with a threshold value, a second means (2) for determining the blackness and whiteness of a converted pixel located within an area defined by these four lattice points according to the blackness and whiteness of pixels of the original image located at four lattice points of a lattice whose lattice spacing is ``; A binary image enlarging/reducing device comprising: a selector (4) for selecting either the output signal of the first means or the output signal of the second means according to an enlargement or reduction magnification.