JPS58215165A - Linear density converting system - Google Patents

Abstract

PURPOSE:To reduce the omissions of both black and white informations and to obtain a reproduced picture more faithful to its original picture, by obtaining the weighted average value of the level of a quantitized picture signal for each picture element when an original analog picture signal is quantitized to a multi-value signal and deciding the level of a linear density converted picture signal corresponding to each picture element on the basis of said weighted average value. CONSTITUTION:An original analog picture signal (a) is supplied to a quantitizing circuit 7 through an input terminal 6 to be quantitized to a multiple value (e.g., 16 values) and therefore turned into a quantitized picture signal (d). The signal (d) is supplied directly to one of the two inputs of an average value circuit 9 and to the other input with a delay equivalent to a line through a 1-line memory 8. The circuit 9 delivers a signal obtained binary coding the weighted average value of those two inputs with a proper slice level in the form of a linear density converted picture signal (e) to an output terminal 10. In such a way, the weighted average value is used to decide the level of the linear density converted picture signal (a) on the basis of the integrated level of two lines of a reading system. This reduces the omissions of black and white informations. When the original analog picture signal (a) into a linear density converted picture signal of 1/2 linear density, it is required to refer not only to lines Ln and Ln+1 but the lines Ln-1 and Ln+2. Thus a reproduced picture faithful to its original picture can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention converts an original analog image signal into 1/N (N
The present invention relates to a linear density conversion method for converting into an image signal with a scanning line density of ≧2).

In a facsimile IJ device, etc., when the scanning line density of the reading system is N times the scanning line density of the recording system, in order to match the scanning line density of the reading system and the recording system, It is necessary to convert the obtained image signal into an image signal with a scanning line density of 1/H of the same signal.

Such linear density conversion can most simply be realized by extracting the image signal one line at a time from every N lines of image signals obtained by the reading system.

FIG. 6(b) shows the result obtained when the image signal obtained by reading the kanji pattern shown in FIG. 5(a) is converted into an image signal with half the scanning line density of the same signal using the method described above. (In this case, 1.3 of FIG. 6(a),
6, 7, and 9th lines are extracted).

Here, FIG. 6(a) shows the positional relationship between the kanji pattern and each pixel (indicated by one square) of the photoelectric conversion element of the reading system.

The line width of the kanji pattern is equal to the aperture size of the photoelectric conversion element, and if the kanji pattern is over 1/2 or more of the aperture, that pixel is black (1" at the binary level). ) and size: i, +2.The rectangular squares shown in Figures 5 (b) to (e) each indicate one record do 2, g (
These circumstances are the same in FIGS. 6 and 7, which will be described later).

As is clear from FIG. 5(b), the above-mentioned simple method has the disadvantage that black information is missing.

For this reason, conventionally, a linear density conversion formula as shown in FIG. 1 has been used (the figure shows the world when the scanning line density is reduced to 1/2). To explain this, 1 is the input terminal, 2
3 is a binarization circuit, 3 is a line memory having a capacity for one line, 4 is an OR gate, and 5il''i output terminal.

The original analog image signal a obtained based on the output of the photoelectric conversion element of the reading system is sent to the 2116 conversion circuit 2 through the input terminal 1.
The signal is manually inputted and then binarized by the same circuit 2 at an appropriate slice level and converted into a binary signal. One input of the OR circuit 4 receives the AI binary signal directly from the binarization circuit 2, and the other input receives the binary signal delayed by one line from the one line memory 3. is input.

The output of this OR circuit 4 is then output to the output terminal 6 as a linear density converted image signal C every two lines of the original analog image signal a.

Therefore, the OR of the current line and the previous line of the binary signal
The result obtained by taking the result in the OR circuit 4 becomes the linear density converted image signal C. That is, two consecutive lines Ln with a reading system shown in FIG. 4(-).

When Ln++ is converted into one line of linear density converted image signal C, the linear density converted image signal C corresponding to the same pixel P1 + P2 in these lines Ln and Ln+1 is converted to pixel P1 or pixel P2. If at least one of the corresponding binary signals is a black signal, it becomes a black signal. Therefore, the black information contained in the original analog image signal a will not be lost.

FIG. 5(C) shows a reproduced image obtained when the original analog image signal a obtained in the state of FIG. 6(a) is subjected to linear density conversion using the conventional method shown in FIG. 1 just described. . As can be seen from the figure, in the conventional method shown in Fig. 1, there is no loss of black information. The black horizontal line is thin,
If the width of the white portion between them is wide, relatively good results can be obtained.

However, as in the case of the kanji patterns in Figures 6(a)- and 7(a), when the black horizontal lines in the 1-Ryo information pattern become thicker and the width of the white part between them becomes thinner, In the conventional method shown in FIG. 1, as shown in FIGS. 6(C) and 7(C), the reproduced image that cannot be obtained lacks white information and has a so-called dull image quality. This had the disadvantage that the image quality deteriorated (see Figure 6(b)).
, FIG. 7(b) is the IL of FIG. 6(a) and FIG. 7(
This shows the reproduced image obtained when the original analog image signal a obtained in condition a) is subjected to linear density conversion using the method described at the beginning, in which one line is extracted for each simple IN line. (The image quality is somewhat poor.)

The present invention was made in order to eliminate the above-mentioned drawbacks of the conventional art, and an object of the present invention is to provide a linear density conversion method that can reduce the loss of black information and white information and obtain an Agyu image that is more faithful to the original image. shall be.

The linear density conversion method according to the present invention creates a quantized image signal by quantizing the original analog image signal into multi-values, and for every N lines of this quantized image signal, The weighted average value of the level of the quantized image signal for each pixel of the same number in each M (M>O) line of This determines the level.

The present invention will be explained in more detail below based on embodiments shown in the drawings.

FIG. 2 shows an embodiment of the present invention in which an image signal obtained by a reading system is converted to a scanning line density of 1/2, where 6 is an input terminal, 7 is a quantization circuit, and 8 is one line. 9 is an average value circuit, and 1o is an output terminal.

In this embodiment, the original analog 60 digit image signal a, which is converted based on the output of a photoelectric conversion element (not shown) in the reading system, is input to the quantization circuit 7 through the input terminal 6. 7, the quantized image signal dK is converted into a multi-valued (for example, 16-valued) 16-r- signal. This quantized image signal d is directly inputted to one of the two inputs of the average value circuit 90, and inputted to the other after being delayed by one line from the one line memory 8[.

Then, the average value circuit 9 outputs a signal obtained by binarizing the weighted average value of the two inputs at an appropriate slice level to the output terminal 10 as a linear density converted image signal e. More specifically, the average value circuit 9 calculates the same number of pixels P1 . When quantized image signals d corresponding to P2 are input to the circuit 9, the values of those quantized image signals d are A(P+) and A(P2), respectively.
Then, the weighted average value is (α・A'('PI)×β・A(P2))/(α+β)
A binarized signal is output to the output terminal 1 as a linear density-converted image signal e corresponding to the pixel P+IP2.

Here, α and β are weighting coefficients that determine which of the lines Ln + Ln+I should have a stronger influence on the linear density-converted image signal e, and α−β−
1, the linear density converted image signal a is A'(P+
) and A (P2), which is the simple average value of 0. The average value circuit 9 outputs the linear density-converted image signal e every two lines of the child image signal d, and the image signal d
, for 2 lines.

One line of linear density converted image signal e is obtained.

Note that the average value circuit 9 can be configured by f(OM or the like) in which output values corresponding to various levels that its two inputs can take are stored.

Figure 6(d) and Figure 6(d,) are respectively Figure 6(a).
), the reproduced image obtained when the original analog image signal a obtained in the state shown in FIG. show. As is clear from these figures, in the method of this embodiment, by using the 0-bit weighted average value, the level of the linear density converted image signal a is determined by the overall level of the two lines of the reading system. Therefore, loss of black information and white information is less likely to occur.

However, in the kanji pattern in Figure 7 (-),
If the width of the black groove line becomes very large and the width of the part between them becomes narrow, even with the method of this embodiment, a slightly soaked shape as shown in Fig. 7(d) can be obtained. There is 1 match which becomes 1+Iri quality (1!4 match in Figure 7(d) is also α-β
-1).

Figure 3 (1, also in cases like the above Figure 7 Ca)
FIG.

In the + example, when converting the original analog double image signal a to the 01/2 (D scanning line inspection IWO line density converted image signal), Furthermore, the Q1 line Ln + before and after that
By also referring to +L+n+2, a faithful reproduced image can be obtained as described above.

To explain this, in FIG. 3, 11 is an input terminal;
12 is a conversion circuit, 13 and 14.1 are each one line memory, and 16 is an average value circuit.

17 is an output terminal.

The original analog image signal a obtained based on the output of the photoelectric conversion element (not shown) of the reading system is input to the input terminal f11'.
The signal is inputted to the quantization circuit 12 through i, and is quantized into multi-values by the same circuit 12, thereby being converted into a quantized image signal f. This refined image blur signal amount is calculated by the average value circuit 16.
to one of the four inputs (・yo, directly, and the other three
Each input has one line memory 13. i4,1
6, the signal is input after being delayed by 1, 2, and 3 lines.

Then, the average value circuit 16 outputs the signal obtained by converting all the four manually weighted average values into 2IIT at an appropriate slice level to the output terminal 17 as a line density variable image (original signal q).

To be more specific, the average value circuit 16 reads four consecutive lines L'n-'l of the reading system shown in FIG. 4(b).
Ln + Ln4-11m. +2 mutually identical pixels P. When the quantized image signal f corresponding to J PI I β2 'l β3 is input to the same circuit 16,
The values of those European image signals ■ are each A(Pa).
, A(P+).

Let A(β2) and A(Ps) be their weighted average value.

(β1・A(Po)+β+・A(P+)+32・A(
β2) 10α2・A(β3))/(α1+α2+β1+β
2) is outputted to the output terminal 17 as a pure density-converted image signal q corresponding to the pixel Po-β3.

Here, β1. β2. β1. β2 is a weighting coefficient, β
1-β2-0, it is the same as in the previous embodiment. Also, β1. While β2 is a negative coefficient, β1. β
If 2 is a positive coefficient, the effect of emphasizing the edges of the image can be obtained simultaneously with pure density conversion.

In this embodiment as well, the average value circuit 16 outputs the linear density image signal q every two lines of the quantized image signal f, so that as a result, the original analog image signal a
One line of the linear density image signal q is obtained for every two lines of .

(e) in FIGS. 5, 6, and 7 shows that β1-β2. =-Q, 5. β1-β2 = 1.6
The reproduced image is shown when χ is used.

Note that by further expanding the method of the embodiment shown in FIG. 3 above,
As shown in FIG. 4(C), the line LHILn+1 and the two lines L before these lines Ln + Ln+ 1
n-2+Ln-1 and the latter two lines "β4-2 +
Ln4-! If the level of the linear density converted image signal is determined with reference to l, a reproduced image that is even more faithful to the original image can be obtained.

Further, in each of the embodiments described above, the linear density converted image signal is a binary code, but the linear density converted image signal may be converted into a multivalued signal by outputting the weighted average value by one inch or the like.

As described above, the linear density conversion method of the present invention has the excellent effect of reducing the loss of black information and white information and obtaining a reproduced image that is more faithful to the original image.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an example of a conventional linear density conversion method, FIG. 2 is a block diagram of a linear density conversion method according to an embodiment of the present invention, and FIG. 3 is a block diagram of a linear density conversion method according to another embodiment of the present invention. A block diagram of the method, FIG. 4(a) is the reference line in the method of FIGS. 1 and 2, FIG. 4(b) is the reference line in the method of FIG. 3, and FIG. 4(C) is the reference line in the method of FIG. An explanatory diagram showing reference lines in a method that further expands the method shown in the figure, and FIGS. 5, 6, and 7 show a comparison of reproduced images obtained by the sub* method and the method according to each of the above embodiments. It is a model diagram. 7...Quantization circuit, 8...1 line memory, 9-pat average value circuit, 12...Quantization circuit, 13
~15...1 line memory, 16...average value circuit, a...original analog image signal, b...quantized image signal, e...line' density conversion image Signal, f...
... Quantization surface 1-image signal, q ... Linear density conversion image signal.

Claims (1)

[Claims] A quantized image signal is created by quantizing the original analog image signal into multi-values, and for every N lines of this quantized image signal, the H line and M (M≧0
) The weighted average value of the level of the quantized image signal for each pixel of the same number in each line is calculated, and based on this weighted average value, the linear density transformed both image signals corresponding to each pixel of the previous RCN line are calculated. A linear density conversion method characterized in that the original analog image signal is converted into the linear density converted image signal having a scanning line density of 1/H of the original analog image signal by determining a level.