JPS5810959A - Picture signal processing system - Google Patents

Abstract

PURPOSE:To decrease the transmission time of a facsimile using a data compressor by the modified Hoffmann system, by switching the slice level of for >=2 picture elements, in a picture signal processing system of a dither system. CONSTITUTION:The transmission time when the pattern change from the slice level pattern of switching at each one picture element toward the main scanning direction as conventional systems to the pattern of switching of at two or four picture elements is made, is as shown in Figure, where E is a picture including an intermediate tone in an original and F is a mixture of characters and a picture including intermediate tone in the original. As a result, the transmission time can considerably be decreased by switching the slice level for two picture elements or over.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a facsimile image signal processing method for reproducing halftones using a dip method, and more particularly to an image signal processing method that takes transmission time into account. An image signal processing method using the dip method is known as a method for reproducing halftones.

In this method, for example, as shown in Fig. 1, a slice level of KO to 15 is set between the sum, white level, and black level, and the analog image polarization corresponding to each pixel output from the COD image sensor of the scanner is calculated. For example, as shown in FIG. 2, each of the 16 different slice levels set above is binarized to reproduce halftones.

'&O, 1 square pixel size in Figure 2, and the number inside it represents the slice level, in the example shown,
The slice level is different for each pixel, and binarization is performed by repeating 4×4 (D slice level) arm turn B.

According to K, there are 17 picture planes with 4x4 pixels as one unit.
Since it can be expressed in gradations, it is possible to reproduce halftones close to the original WijlK.

However, in this type of conventional image signal processing method, as seen in the conventional example above, the rounding, which performs binarization by switching the slice level for each pixel, is When encoded and transmitted using the Hoff 1 method, the black or white run length is shortened to 1, unless the halftone is extremely close to black or white, resulting in poor encoding efficiency and longer transmission time. There were drawbacks.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image signal processing method that can shorten transmission time by eliminating the drawbacks of the above-mentioned conventional techniques in the dip method.

In order to achieve this object, the present invention is characterized in that a plurality of slice levels are switched at least every two pixels in the main scanning direction.

That is, the applicant has changed the number of pixels when switching the slice level from 9 turn B in the conventional method, which switches the number of pixels for each pixel in the main scanning direction shown in FIG.
The pattern C1 of switching every pixel was further changed to a pattern D of switching every 4 pixels shown in FIG. 4, and the transmission time and reproduced image were investigated.

As a result, the results shown in FIG. 5 regarding the transmission time were obtained. Here, E is an example of the experimental results when the original contains only pictures containing halftones, and F is an example of the experimental results when the original contains pictures containing halftones and text.

As is clear from this result, if the slice level is switched every two or more pixels, the transmission time can be considerably shortened.

On the other hand, regarding the halftone reproduction image, although it cannot be shown in the drawings, the image quality gradually decreases as the number of switching pixels increases, but even if the number of switching pixels and primes is increased to 4 pixels, the intermediate level is still sufficient for practical use. A clear image was obtained.

Furthermore, as shown in FIG. 6, there is a mixed luster turn of the straight turn C and the arm turn σ, which is shifted by 2 bits in the main scanning direction, and furthermore, as shown in FIG. An attempt was made to binarize this by using a mixed turn with a turn d shifted by 4 pi in the main scanning direction.

As a result, it was found that although the transmission time did not change, the image quality of the halftone reproduced image was improved compared to the cases of FIGS. 3 and 4.

From the above, if the slice level is switched for two or more pixels, the transmission time will be shortened.

The present invention has been made based on such experimental results, and specific examples thereof will be described below with reference to FIGS. 8 and 9.

FIG. 8 shows a configuration diagram of a facsimile transmission side image signal processing circuit when the analog image signal output from the CCD image sensor is binarized at the slice level shown in FIG. 5. , l is a timing signal generator that generates a sub-scanning clock, ri a, and a main scanning clock b, 2 is a CCD image sensor that outputs an analog image signal C synchronized with the main scanning black and ri b, and 3 is a main scanning clock b. A binary counter that divides the frequency by A, 4 a quaternary counter that counts its W frequency-divided output and the output from the circuit 5, 6 a quaternary counter that counts the sub-scanning clock a, and 7 a sub-scanning clock. Binary counter to divide scanning clock a by 174, 8 is 1
ROM stores digital data representing six slice levels; 9 is a peak hole P circuit that holds the peak value of analog image signal C; 10 is ROM 8; digital data output from 8 corresponds to the peak value; A D/A converter 11 converts the analog image signal C into a slice level, and a comparator 11 compares the analog image signal C with the slice level and converts it into a binary value.

Now, when the document reading device is started, as shown in the timing chart of FIG.
, and one main scanning clock b for each pixel.
occurs. In synchronization with this main scanning clock signal b, the CCD image sensor 2 outputs an analog image signal C proportional to the amount of light received at that time.At this time, the quaternary counter 6 counts the sub-scanning clock signal a. The count value d is output to the ROM 8K. At the same time, the quaternary counter 4 counts the main scanning clock b every 2 bits and outputs the counted value to the ROM 8. The ROM 8 selects one of the 16 pieces of data stored in the ROM 8 using the count value d, · as an address and outputs it to the D/A converter 10.

As a result, from the ROM 8, four data different for each line are selected and outputted every two pixels.
The slice level g is converted to a slice level g corresponding to the peak value outputted from the peak value, and is output to the comparator 11. Comparator 11 FiCCD
By comparing the analog image signal C output from the image sensor 2 with the slice level g, it is output as a binary heel digital image signal to an encoding device (not shown).

Therefore, the first four lines of analog image signals output from the CCD image sensor 2 are converted into an 8x4 slice Leperno Q-turn C which is switched every two pixels as shown in FIG. It will be binarized repeatedly.

The analog image signals for the next four lines are also summed and binarized as described above, but at this time, the output l of the binary counter 7 becomes "1", and the AND circuit 5 is opened. Therefore,
The sub-scanning black and white signals generated from the timing signal generator 1
is input to the quaternary counter 4 via the piece circuit 5, and before the output from the binary counter 3 is input to the quaternary counter 4, the counted value: is incremented by ].

As a result, for the next 4 lines of analog image signals, the first 4 lines are shifted by 2 pixels at 9 slice levels/
Binarization is performed at parable turn σ.

In this way, by encoding and transmitting the binarized digital image signal, the receiving side can obtain a halftone image with almost the same quality as the conventional method shown in FIG. As shown in the figure, if the original is only a picture containing halftones, the transmission time can be reduced by about half.

Incidentally, if the Φ circuit 5 shown in FIG. 8 is removed, the analog image signal output from the CCD image sensor 2 is
Binarization is performed at /l turn C of the slice level shown in the figure. On the other hand, if a quaternary counter is used instead of the binary counter 3, the analog image signal C output from the CCD image sensor 2 is converted into a binary value by the slice-level data turns D and d shown in FIG. Furthermore, at this time, except for the - circuit 5, binarization is performed at turn 79 D in FIG. Similarly, switching every 3 pixels or every 5 pixels can also be performed on the product.

As described above, according to one aspect of the present invention, in the image signal processing method using the dip method, the slice level is switched for two or more pixels, so that the required transmission at a factor < IJ using a data compression device using the modified Hoffman method You will be able to save time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a general slice level setting state in the DIP method, FIG. 2 is a pattern diagram of ff2+slice level in the DIP method, and FIGS. 3 and 4 are slices according to each embodiment of the present invention. Level 74 tan diagram, 5th
The figure is a correlation diagram between the number of switching pixels of the slice level and the transmission time, Figures 6 and 7 are four-turn diagrams of the slice level according to each embodiment of the present invention, and Figure 8 is an example of an embodiment of the present invention. FIG. 9 is a block diagram of the image signal processing circuit according to the invention, and FIG. 9 is a time chart for explaining the operation of FIG. 1... Timing signal generator, 2... COD image sensor, 3.7... Binary counter, 4.6...4
Road counter, 5...AND circuit, 8...ROM, 9
...Peak hold circuit, 10...1 converter, 11
...Comparator. Figure 1

Claims (1)

[Claims] An image signal processing method for reproducing halftones using the dip method, which is characterized in that slice levels in the main scanning direction are switched every two or more pixels.