JPH01160167A - Picture signal processing method - Google Patents

Abstract

PURPOSE:To simply trim a frame area by obtaining an output level range of a peak of a histogram with respect to an area not including a picture and eliminating the output level range of the peak from the picture signal of the area including the picture. CONSTITUTION:A CPU obtains a histogram b1 of a picture signal (a) and since the histogram b1 has a peak corresponding to the lightness of the frame area, the output level range (c) of the peak is obtained. Moreover, the CPU moves a line sensor 30 and when the sensor reaches a location including the picture A, the picture signal a2 at that time is stored in a memory and the histogram b2 is obtained from the picture signal a2. Then the CPU obtains a new histogram (b2-b1) being the result of eliminating the output level range (c) of the frame area obtained by a histogram means I46. Thus, the picture signal level of the frame area is obtained from the density histogram to eliminate the picture signal of the picture signal level of the frame area in the picture signal of the picture area including the original. Thus, the frame area is trimmed by the simple method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image signal processing method for obtaining an image signal by scanning an image having a document portion and a frame portion surrounding the document portion.

(Technical Background of the Invention) When holding a negative microfilm in a film holder and projecting its image onto a screen, a bright frame portion around a portion of the film (g m m minutes) that does not pass through the film is projected onto the screen. appear.

Furthermore, if the positive microfilm itself has a black frame around the original portion, the projected image will have a black frame around the film image.

In this way, when a bright frame is formed around a negative original or a dark frame is formed around a positive original, if this image is positively copied as is, the frame portion will appear black. Therefore, various trimming methods have been proposed to delete this black frame portion.

For example, a method can be considered that detects the coordinates of a document portion in an image and changes image signals other than the document portion to a white level. However, it is difficult to detect the coordinates of the manuscript part with high precision.
In particular, when the shape of the document is complex, the algorithm for detecting it becomes complex.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and it provides a simple method to remove the frame area when reading an image having a frame area without borders around the document and obtaining a hard copy of the image. It is an object of the present invention to provide an image signal processing method that performs cropping and prevents the crop from appearing black.

(Structure of the Invention) According to the present invention, it is an object of the present invention to provide an image signal processing method for obtaining an image signal by scanning an image having a frame area without an image around a document portion. Determine the image signal level of the frame area from the histogram,
This is achieved by an image signal processing method characterized in that the frame area is trimmed by deleting an image signal having an image signal level of the frame area from among the image signals of the image area including the document.

(Example) Figure 1 is a block diagram showing an example of the method of the present invention, and Figure 2 is a block diagram showing an example of the method of the present invention.
The figure shows an example of application to this micro league, Figure 3 shows the image on the screen, Figures 4A-C are output waveform diagrams of each processing stage of the image signal, and Figures 5A-C are density histograms. FIG.

In FIG. 2, reference numeral 10 denotes a light source, and the light from this light source 10 is guided to a microfilm 18 as an original via a condenser lens 12, a heat shielding filter 14, and a mirror 16. The light transmitted through this microfilm 18 is guided to a transmission screen 28 by a projection lens 20 and mirrors 22, 24, 26, and an image of the microfilm 18 is formed on this screen 28.

A CCD line sensor 30 is arranged on the back side of the screen 28 so as to be movable up and down. That is, this line sensor 30 is arranged long in the direction transversely across the screen 28, and the line sensor 30 performs main scanning by reading out image signals in the length direction and sequentially outputting image signals as time-series signals. Sub-scanning is performed by moving the sensor 30 in the vertical direction. The image signal a of this line sensor 30 is sent to the CPU via an input interface 32.
34, various processes are performed as will be described later, and after the frame area of the document is trimmed, it is output to the printer 38 via the output interface 36. The cropped image is then printed out to obtain a hard copy. Further, the output of the CPU 34 can be recorded in an external storage device such as an optical disk device 40. Therefore, if necessary, a necessary original image may be read out from the optical disk device 40 and printed out by the printer 38. Note that 42 is a memory of the CPU 34.

The CPU 34 sequentially performs the operations shown in FIG.
The PU 34 first performs main scanning by placing the line sensor 30 at position 3OA in FIG. 3, which is a frame area with no image on the screen 28, and stores the image signal a at this time in the memory 42 (see FIG. 1). memory means 44). Film 18 is negative.

When a bright frame area appears around the image A (FIG. 3), the image signal a at this time becomes a high output level as shown in FIG. 4A. In FIG. 4, the horizontal axis represents time t (or pixel order), and the vertical axis represents output level h.

The CPU 34 obtains a histogram b of this image signal a (FIG. 1, histogram means 146). As shown in FIG. 5A, this histogram b1 has one peak corresponding to the brightness of the frame area, and the CPU 34 determines the output level range C of this peak. In FIG. 5, the horizontal axis represents the output level H, and the vertical axis represents the frequency H. On the other hand, the CPU 34 moves the line sensor 30 to position 30B (
3), the image signal a2 at that time is stored in the memory 42 (memory means 44). This image signal a2 includes signals of an image portion and a frame portion as shown in FIG. 4B. The CPU 34 generates a histogram b from this image signal a2.
2 (Fig. 5B) (histogram means II 4
8). As shown in FIG. 5B, this histogram b2 has a peak B for the frame area and a peak C for the background of image A, and the signal for image A is included between Okayama B and C.

The CPU 34 deletes the output level range C of the frame area obtained by the histogram means I46 from the histogram b2 of FIG. 85B, and obtains a new histogram (b2-tz) (histogram means 50). The CPU 34 determines the binarization level d based on this histogram (bl-b+) (binarization level setting means 52). This binarization level d can be determined as a point E on the signal level side of the image among two intersections where the constant frequency h1 intersects with the peak C of the histogram (b2-b+), as shown in FIG. 5C. Further, the binarization level d may be set as an output level that is shifted by Δ from the point where the constant frequency h2 intersects with the mountain C to the signal level side of the image.

In this way, the binarization level d is set between the background peak and the signal level containing the image by various methods.

On the other hand, when the output level range C of the frame area is determined by the histogram means 46, the CPU 34 calculates the output level range C from the image signal a2 including the image (see FIG. 4B).
(image signal deletion means 54), thereby removing the signal for the frame area from the image signal a2, leaving only the signal for the area of the image A, and obtaining the image signal a3 shown in FIG. 4C. . The CPU 34 binarizes this image signal a3 using the already determined binarization level d, and outputs a binarized signal e (comparison means 56). This binary signal e is output to the printer 38, where a hard copy is obtained.

In the above embodiments, a case has been described in which a bright frame area exists around the negative image A, but the present invention is not limited to this, and is also effective when, for example, a dark frame area exists around a positive image. . FIGS. 6A to 6C show image signals a1. a2. a3, and Figures 7A-C are histograms b+
, b2° (b2-b+), and each figure shows the above-mentioned 4th A-C.
5A and 5A-C, the description thereof will not be repeated.

In the above explanation, an embodiment applied to a micro league has been described, but the present invention is not limited thereto, and can also be applied to a copying device and the like. For example, this is also effective when the background of the original to be copied is set darker than the text or graphics of the original.

(Effects of the Invention) As described above, the present invention obtains the output level range of the peak of the histogram for an area that does not include an image, and deletes this output level range of the peak from the image signal of the area that includes the image. , you can easily and accurately trim the frame area.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the operation of one embodiment of the method of the present invention, Fig. 2 is a conceptual diagram of a microreader to which this method is applied, Fig. 3 is a diagram showing a screen image, and Figs. 4A-C are processing stages. Figures 5A-C are diagrams showing histograms; Figures 6A-C are output waveform diagrams of image signals at each processing stage in other embodiments; Figures 7A-C are diagrams showing histograms. It is a diagram. 30... Line sensor, al + a2, a3 "" image signal, bl, b2
．． b3...Histogram, A...Image.

Claims (1)

[Scope of Claims] An image signal processing method for obtaining an image signal by scanning an image having a frame area without an image around a document portion, the image signal of the frame area being determined from a density histogram of the image area that does not include the document. An image signal processing method comprising: determining a level, and trimming a frame area by deleting an image signal having an image signal level of the frame area from among image signals of an image area including the document.