JPH03136468A - Picture signal processor - Google Patents

Abstract

PURPOSE:To obtain a more suitable picture with a binary picture such as a character and a half-tone picture such as a photograph by providing an emphasis degree varying means to vary the emphasis degree of an edge emphasis circuit. CONSTITUTION:When an input picture signal is the binary picture signal such as the character a first switch 9 of an edge emphasis circuit 3 is set to the side of a contact 9a by the output of an identifier circuit 10. Accordingly, the gain of an amplifier 8 is increased and the emphasis of an edge is enlarged. Then, since a second switch 15 is turned to the side of a contact 15a, a fixed threshold value circuit 13 is selected and the picture signal is made binary. In the case of the half-tone picture signal such as the photograph since the first switch 9 is set to the side of a contact 9b, the gain of the amplifier 8 is decreased and the signal is transmitted in a state without edge emphasis. Then, since the second switch 15 is set to the side of a contact 15b, the input picture signal receives a binary operation in a dither circuit 14. Thus, in the case of the binary picture such as the character resolution is improved and in the case of the half-tone picture such as a photographic original, the picture of a smooth continuous tone can be reproduced without generating a contour.

Description

[Detailed Description of the Invention] The present invention relates to an image signal processing device, and more specifically to an image signal processing device used in a digital copying machine, facsimile device, etc. that reads an image pixel by pixel. It relates to a processing device.

Prior Art A conventional example of such an image signal processing device is disclosed in Japanese Patent Application Laid-Open No. 63
The techniques disclosed in Japanese Patent Application Laid-Open No. 205239-205239 and Japanese Unexamined Patent Publication No. 63-209275 can be mentioned. The former automatically distinguishes a document image into photo areas, text areas, and halftone dot areas, and selects and uses the corresponding binarization circuit for each head area to obtain an appropriate image. The latter is designed to vary the degree of emphasis of the edge emphasis processing of the read image in accordance with the magnification ratio.

In the above-mentioned Japanese Patent Application Laid-Open No. 63-205239, the binarization level is changed depending on the type of image, so it can be said that binarization suitable for each image can be realized. However, for thin lines such as characters in images, it is difficult to say that sufficient image quality can be obtained simply by changing the binarization level. Further, in the above-mentioned Japanese Patent Laid-Open No. 63-205239, it is not possible to vary the emphasis depending on the type of image such as text or photographs.

The present invention has been made in view of these points, and it is an object of the present invention to provide an image signal processing device that can obtain more appropriate images from binary images such as characters and halftone images such as photographs. purpose.

In order to achieve the above object, the image signal processing device of the present invention includes an edge emphasis circuit that performs edge emphasis of an input image signal;
The apparatus includes a binarization circuit that converts the output of the edge emphasis circuit into a binary signal, and an emphasis degree variable means that changes the emphasis degree of the edge emphasis circuit. In this case, the degree of emphasis may be manually set using a manual adjustment member, and the input image signal may be
It may also be set automatically based on the output of a discriminator that identifies whether it is a value image or a halftone image. Furthermore, when an image signal with a variable degree of edge enhancement is to be binarized, it is preferable that the fixed dark value circuit and the dither circuit be selected according to the output of the discrimination means before the binarization is performed. Note that the identification by the identification circuit may be performed based on the frequency of the input image signal.

The image signal processing device of the present invention also includes an edge emphasis circuit that emphasizes the edges of a human-powered image signal, and a second circuit that is connected after the edge emphasis circuit and converts the input image signal into a binary signal.
The image processing apparatus may be configured to include a value converting circuit and a switching means for switching between a state in which edge emphasis is performed and a state in which the edge emphasis is not performed by the edge emphasis circuit.

Furthermore, an edge enhancement circuit that digitally enhances edges of an input image signal, a binarization circuit that converts an output of the edge enhancement circuit into a binary signal, and means for selecting an enhancement degree of the edge enhancement circuit; It may be configured to have.

Effects According to the configuration of the present invention, for example, in the case of a binary image such as a character, by sufficiently emphasizing edges,
A clear character image can be formed, and in the case of a half-tone image such as a photographic image, a good half-tone image without false contours can be formed by weakening or not emphasizing edges.

Back Jul The embodiments shown in the drawings will be described below.

In FIG. 1, (1) is an image sensor that reads the original image, such as a CCD (charge transfer device) or a MOS-IC.
Consists of etc. The output of this image sensor is amplified by an amplifier (2) and then given to an error/age enhancement circuit (3). This edge emphasis circuit (3) is connected to a straight line (4) that leads the input image signal from the amplifier (2) directly to the output side.
) and an edge emphasis component forming line (5),
The outputs of both lines (4) and (5) are combined by an adder (6). The edge emphasis component forming line (5) includes a second-order differential circuit (7) that outputs a second-order differential signal as shown in FIG. 2(b) corresponding to the edge portion of the input image signal, and amplifies the output. It consists of an amplifier (8) for changing the gain of the amplifier (8), a first switch (9) for changing the gain of the amplifier (8), a resistor (R+) (R1) for determining the gain, etc. The first switch (9) may be switched by an operation key provided on an operation unit (not shown), but in this embodiment, it is automatically switched by an identification circuit (lO) that identifies the image of the input image signal. It is designed so that it can be switched at will. Identification circuit (1
0) has a high frequency when the input image signal is a binary image signal as shown in Figure 3 (a), and when it is a halftone image signal such as a photographic image, the frequency is high as shown in Figure 3 (b). The low frequency of the signal is used to identify whether it is a binary image signal or an intermediate image signal. Then, when the signal is a binary image signal, the first switch (9) is set to the contact (9a) side to increase the gain of the amplifier (8), and when the signal is a halftone image signal, it is set to the contact (9b) side. to lower the gain.

Returning to FIG. 1, the output of the adder (6) is converted from an analog signal to a digital signal by the next AD converter (11). After being A/D converted, the input image signal is converted into a binary signal by the binarization circuit (12), but in this case, the input image signal is
The digitization circuit (12) has a fixed dark value circuit (13) that has a single reference level for binarization, and a dither circuit (14) that has a plurality of reference levels. A switch (15) selects one of these circuits (13) and (14). The second switch (15) and the first switch (9) are switched and driven by the output of the identification circuit (10). Then, Mr. M changed the input image signal to 2.
In the case of a value image signal, it is set on the contact point (15a) side, and in the case of a halftone image signal, it is set on the contact point (15b) side.

The output of the binarization circuit (12) is sent to a printer (16), where an image is formed.

Now, in FIG. 1, when the input image signal is a binary image signal such as a character, the first switch (
9) is set on the contact (9a) side by the output of the identification circuit (step 0), the gain of the amplifier (8) increases and the level of the second-order differential signal shown in FIG. 2(b) increases. Therefore, when combined with the original signal transmitted through the straight line (4) (Fig. 2(a)), the edges of the input image signal are greatly emphasized as shown in Fig. 2(c). ,
The fully edge-enhanced human image signal is sent to an A/D converter (
11), it is converted into a digital quantity, and then the binarization circuit (1
2), but at this time the second switch (15)
is on the contact point (15a) side by the identification circuit (lO), the fixed threshold circuit (13) is selected, and the input image signal is binarized by comparison with one reference level.

Next, when the input image signal is a halftone image signal such as a photographic image, the first switch (9) in the edge emphasis circuit (3) is switched to the contact point (9b) by the output of the identification circuit (10).
) side, the gain of the amplifier (8) decreases by 2
Since the level of the second differential signal is very small, the adder (
The output of 6) is A/D converted with little edge emphasis or almost no edge emphasis, and then sent to the binarization circuit (1
2). At this time, the second switch (15) of the binarization circuit (12) is set to the contact (15b) side according to the output of the identification circuit (10), so the input image signal is binarized by the dither circuit (14). It will be affected.

FIG. 4 shows a specific example of the binarization circuit (12). In the figure, (17) is a digital comparator, one input A of which is an input image signal given through an A/D converter (11), and the other input B is a reference level signal. The output of the fixed dark value circuit (13) or the output of the dither circuit (14) is selected by a channel selector (15°) constituting the second switch (15) and is given as the reference level signal (ie, human power B). The channel selector (15') is an identification circuit (10) shown in FIG.
) is controlled by the output of The dither circuit (14) is R
It is composed of an OM (read only memory), and a line signal is applied through a row counter (18), and a pixel clock is applied through a column counter (19). The above-mentioned human power A and large input are both 8-bit configuration in this embodiment, so input C is input from the fixed dark value circuit (13) to the channel selector (15°) and input C is input from the dither circuit (14) to the channel selector (15'). ) also has an 8-bit configuration.

2 when the output (input D) of the dither circuit (14) is given as input B to the digital comparator (17).
(The concept of a conversion is shown in Figure 5. In the figure, (
(a) shows a matrix input image signal (input A), and (b) shows data (manual input D) from the dither circuit (14). Further, (c) shows the binarized result obtained by comparing (a) and (b). Incidentally, the digital comparator (17) is 0.0 if input A and input B are A2B. If A<8, l is output.

In the embodiment shown in FIG. 1 described above, the degree of edge enhancement of the edge enhancement circuit (3) is controlled by changing the gain of the amplifier (8), but as shown in FIG. The gain is configured to be constant in advance, and the output of this amplifier (8) is sent to the adder (
6) may be configured to be transmitted or blocked. In this case, if it is a binary image signal, the amplifier (8)
The output is transmitted to an adder (6), and if it is a halftone image signal, it is cut off.

FIG. 7 shows an embodiment in which a digital filter (not shown) is used as a filter for the edge emphasis circuit, in which the edge emphasis circuits (3a) and (3b) are connected to the A/D converter (
It is inserted after 11). Here, the first switch (9) is omitted by providing two edge enhancement circuits, but it is also possible to provide only one edge enhancement circuit and provide the first switch (9) instead.

Also, as mentioned above, according to the present invention, the resolution of binary images such as characters is improved, and the resolution of half-tone images such as photographic originals is improved without contours and smooth continuous tone. The present invention is extremely useful because it has the effect of reproducing images.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image signal processing device embodying the present invention, FIGS. 2 and 3 are signal waveform diagrams for explaining the same, and FIG. 4 is a specific configuration diagram of a binarization circuit. , FIG. 5 is a conceptual diagram showing binarization using a reference signal of a dither circuit. FIG. 6 is a circuit diagram of a main part of another embodiment of the present invention. FIG. 7 is a block diagram of still another embodiment of the present invention. (3) (3a) (3b) - Edge enhancement circuit (5)
- Edge emphasis component forming line (8)...Amplifier, (9)...First switch. (10)--one identification circuit, (12)-binarization circuit. (13) ---One fixed threshold circuit, (14)--Dither circuit. (15)・-Second switch.

Claims (11)

[Claims] (1) An edge enhancement circuit that enhances the edges of an input image signal, and 2 that converts the output of the edge enhancement circuit into a binary signal.
An image signal processing device comprising: a value converting circuit; and an emphasis degree varying means for varying the emphasis degree of the edge emphasis circuit. (2) The image signal processing device according to claim 1, wherein the emphasis degree variable means includes a manual operation member. (3) The emphasis degree varying means has identification means for identifying whether the input image signal is a binary image signal or a halftone image signal, and the emphasis degree is varied based on the output of the identification means. The image signal processing device according to claim 1, characterized in that: (4) The binarization circuit includes a fixed threshold circuit that provides a reference value for comparing the magnitude of the input image signal, a dither circuit, and the fixed threshold circuit and the dither circuit based on the output of the identification means. The image signal processing device according to claim 3, further comprising a switching circuit for switching. (5) The input image signal is set to 2 by the output of the identification circuit.
When the input image signal is a value-based image signal, the degree of emphasis of the edge enhancement circuit is high and a fixed threshold circuit is selected, while when the input image signal is an intermediate image signal, the degree of emphasis is low and a dither circuit is selected. An image signal processing device according to claim 4, characterized in that: (6) The identification circuit according to claim 3 or 4, wherein the identification circuit identifies whether the input image signal is a binary image signal or a halftone image signal based on the frequency of the input image signal. Image forming device. (7) An edge emphasis circuit that emphasizes the edges of the input image signal, a binarization circuit connected after the edge emphasis circuit that converts the input image signal into a binary signal, and edge emphasis performed by the edge emphasis circuit. An image signal processing device comprising: switching means for switching between a state and a non-active state. (8) The image signal processing device according to claim 7, wherein the switching means has a manual operation member. (9) The switching means has identification means for identifying whether the input image signal is a binary image signal or a halftone image signal,
9. The image signal processing apparatus according to claim 8, wherein the switching is performed based on the output of the identification means. (10) The switching means switches to perform the edge enhancement when the input image signal is a binary image, and not to perform the edge enhancement when the input image signal is a halftone image signal. No. 9 characterized by switching
An image signal processing device according to the claims. (11) An edge emphasis circuit that digitally performs edge emphasis on an input image signal, a binarization circuit that converts the output of the edge emphasis circuit into a binary signal, and means for selecting the degree of emphasis of the edge emphasis circuit. An image signal processing device comprising: