TW560173B - Automatically adjusting line art threshold method and apparatus - Google Patents

Abstract

An automatically adjusting line art threshold method is disclosed. The invention comprises the following steps. Firstly, a start density value, a finish density, a white percentage threshold, a black percentage threshold and a threshold specification value are set. Then a calibration chart comprising at least one density unit and having gray-scale values varying continuously from full whiteness to full darkness is scanned. The calibration chart can be built in an image scanner or be placed on transparent scanning sheet by a user. A line art threshold value is calculated by the start density value, the finish density, the white percentage threshold and the black percentage threshold. Finally, the threshold specification value is compared to the line art threshold value.

Description

560173 V. Description of the invention (1) 5-1 Field of the invention: The present invention relates to a method for automatically adjusting a threshold dichroic day quality grayscale value, in particular to a correction table to automatically adjust a threshold dichroic image quality Method of grayscale value. 5-2 BACKGROUND OF THE INVENTION: Optical scanners are used to capture and digitize images. For example, optical scanners are most commonly used to capture text or other images printed or printed on flat paper. The captured image is then digitized and stored or further processed by character recognition software to generate text from the American Standard Code for Information Interchange A SC I I. A typical optical scanner includes a light source, a linearly arranged photo-sensing element (usually a charge-coupled element CCD, complementary metal oxide semiconductor transistor CMOS and CIS), an analog amplifier (Analog Amplifier), and an analog digital converter Device, a control unit (Controller) and a memory element. The photo-sensing element contains a large number of linearly-coupled charge-coupled elements (CCDs). Each charge-coupled element CCD can capture the optical signal of a single pixel of the image. A full row of charge-coupled device CCD can capture the optical signal of a whole row of pixels in the image. By scanning across the entire document, the CCD can receive the image light signal of the entire document.

560173 5. Description of the invention (2) The process of converting the optical signal reflecting or scanning the self-scanning document into a digital signal includes three steps. First, each photo-sensing element converts the received light signal into an electric charge, and the amount of electric charge depends on the intensity of the light and the exposure time. Secondly, the charge generated by the photo-sensing element is converted into an analog voltage by an analog amplifier. Finally, the analog voltage is digitized by the analog-to-digital converter for digital image processing and storage in the memory device.

The two-color line art (Line Art) is represented by a plurality of digitized gray scale values ^. In the image scanner, the threshold gray level value of the threshold two-color image quality (Line Ari Threshold) is a threshold value of a light-dark boundary, that is, the gray level value is higher than the threshold two-color, the day quality is "dark", and the gray level value For grayscale values below the threshold two-color level, see = "Bright" or "Bright". For example, if the grayscale value is from 0 to 255, "; i = color level image quality gray level value is" 2 5 5 ", and the brightest two-color level value is" 0 ", then the threshold is The grayscale value of the two-color-gradation image quality can be "the value is human. The gray-scale value of the two-colorscale image quality value is" 126 ". 0 to 25 5,

In the device, the threshold is two colors; some high-level image sweeping adjustments are not only X Ϊ manual adjustments. However, it is convenient to find t, and it is not accurate enough. Therefore, it is very necessary to refer to the method of automatically adjusting the threshold grayscale value of the threshold two-color image quality to make it easier for the user or manufacturer to adjust the image scanner's image quality.

560173 V. Description of the invention (3) 5-3 Purpose and summary of the invention: One object of the present invention is to provide a method for automatically adjusting the threshold value of the grayscale value of the threshold dichroic image quality, so that the user of the image scanner can more easily adjust it. The dichroic diurnal grayscale value of the image scanner.

Another object of the present invention is to provide a simple and efficient method for adjusting the threshold dichroic diurnal grayscale value.

In order to achieve the above-mentioned object, the present invention proposes a method for automatically adjusting the threshold grayscale value of the threshold dichroic image quality. The method includes the following steps. First set an initial light and dark density, a final light and dark density, a threshold brightness percentage, a threshold darkness percentage, and a two-color-scale image quality threshold specification value. Then, a calibration table is scanned. The calibration table includes at least one light-dark density region, and the light-dark density region has a grayscale value that changes continuously from full darkness to full brightness. This calibration table can be built into the image scanner or placed on the transparent scanner board of the image scanner by the user. Then calculate a threshold dichroic daylight grayscale value based on the initial light and dark density, the final light and dark density, the threshold brightness percentage, the threshold darkness percentage and the scan correction table results. Finally, the threshold dichroic day quality grayscale value is compared with the dichroic image quality threshold specification value. When the above-mentioned threshold dichroic day quality grayscale value is equal to the dichroic day quality threshold specification value, the dichroic image quality threshold specification value is stored. But when the above-mentioned threshold dichroic day quality

Page 7 560173 V. Description of the invention (4) When the grayscale value is smaller than the dichroic image quality threshold specification value, increase the dichroic image quality threshold specification value until the dichroic daylight quality threshold specification value Equal to the threshold dichroic diurnal grayscale value. Conversely, when the threshold dichroic day quality grayscale value is greater than the dichroic day quality threshold specification value, the dichroic image quality threshold specification value is reduced until the dichroic image quality threshold The limit specification value is equal to the threshold dichroic day quality grayscale value. The foregoing brief description of the invention and the following detailed description are examples only and are not limiting. Other equivalent changes or modifications that do not depart from the spirit of the invention should be included in the patent scope of the invention. 5-4 Detailed description of the invention: What must be explained here is that the method for automatically adjusting the threshold dichroic daylight grayscale value described below includes only necessary components and steps. At the same time, the present invention can be implemented by various conventional software and hardware, and only the system and operation mode required for understanding the present invention are mentioned here. The following detailed description will be made according to the accompanying drawings of the present invention. Please note that the drawings are simple forms. Referring to the first figure, a calibration table or light-dark density table of the present invention is shown. This correction table contains at least one light and dark density area, but the first figure has six light and dark density areas. This calibration table can be built into the image scanner or placed on the transparent scanner board of the image scanner by the user. Light and dark density area 1 1 0 means the most

560173 V. Description of the invention (5) Dark grayscale image and light and dark density area 1 0 2 represents the brightest grayscale image. The number of light and dark density @ is arbitrary, and the brightness value is continuously changed from full darkness to full brightness or if 2 5 6 grayscale or 8-bit is selected, the grayscale value is continuously changed from 0 to 2 55. At this time, the grayscale value of the threshold two-color level image quality is 1 2 7 and the grayscale image with a grayscale value higher than 1 2 7 is visible or dark. Refer to the second figure. Flow chart of the method for limiting the gradation value of two-level grayscale value j. After starting in step 202, set the following parameters in step 204. The parameters include the initial light and dark density Sd, the final light and dark density Fd, and the threshold brightness percentage Wp. , Threshold darkness percentage Bp and dichroic image quality threshold specifications W / B — _t 3 The initial light and dark density Sd and the final light and dark density Fcm are used to determine the length or number of pixels of the light and dark density area. For example, if The user of the image scanner sets the initial light and dark density Sd to a digital grayscale value of 1 (30, and the final light and dark density) 7d is \ 2 0 0, and selects four light and dark density regions. The length grayscale value of the light and dark density is 2 5. Threshold brightness percentage ψ p and threshold darkness percentage Bp are used to define and identify light and dark. For example, if the threshold brightness percentage Wp is set to 7 5%, which means that when the bright pixels exceed 7 5%, the gray-scale image legislation > Tian is set as factory bright j ° If the threshold darkness percentage Bp is set to 80% At 80%, the grayscale image is judged as "dark j 0 color level day quality threshold specification value W / B-t is the specification value that the user wants to obtain. After scanning the cat calibration table in step 20, In step 208, the limit value «ν service color level quality gray level value W / B_d is calculated. The threshold two color level image quality gray level value W / B_d is determined from the initial light and dark density Sd, the final light and dark density Fd, and the threshold The brightness percentage Wp is limited to the dark limit IrLR Jtt and the percentage percentage Bp is calculated from the results of the scan correction table.

560173 V. Description of Invention (6) Next, in step 210, the threshold gradation value W / B_d of the two-level image quality threshold is compared with the threshold value W / B_t of the dichroic image quality threshold. If the threshold dichroic day quality grayscale value W / B__d is not equal to the dichroic day quality threshold specification value W / B_t, then in step 2 1 2, further review the threshold dichroic image quality grayscale value w / B — Whether d is greater than the two-level image quality threshold specification value W / B_t. If the threshold gradation value of the two-level grayscale image quality is ~ /: 6_ ^ is greater than the threshold value of the dichroic daytime quality threshold 1/6 ^, then the dichroic image quality threshold value is added to the threshold in step 214. The gradation value W / B_d of the two-level image quality is compared until the threshold value W / B_t of the two-level image quality threshold is equal to the threshold gradation value W / B — d of the two-level image quality threshold. Conversely, if the grayscale value W / B_d of the threshold two-color image quality is smaller than the threshold w / B — t of the two-color image quality threshold value, then the two-color image quality threshold value is reduced in step 21 6. The value W / B — t is re-compared with the threshold two-color image quality grayscale value W / B-d until the two-color day quality threshold specification value W / B — t is equal to the threshold two-color image quality gray scale Up to the value w / B-d, and Γ is followed by step 2 1 8, the two-level image quality threshold specification value w / B — t is stored. The above detailed description of the invention is merely an example and not a limitation. Other equivalent changes or modifications that do not depart from the spirit of the present invention should be included in the patent scope of the invention. also

560173 Brief description of the drawings In order to make the other objects, features, and advantages of the present invention clearer and easier to understand, a preferred embodiment is described below in conjunction with the accompanying drawings to make a detailed description as follows: The first diagram shows The calibration table of the present invention; and the second figure shows a flow chart of the "method for automatically adjusting the threshold gray-scale value of the dichroic image quality" of the present invention. Symbols of the main parts: 1 0 2 light and dark density area 1 0 4 light and dark density area 1 0 6 light and dark density area 10 8 light and dark density area 1 1 0 light and dark density area 2 0 2 start 2 0 4 set the initial light and dark density Sd, and finally Brightness and darkness density Fd, threshold brightness percentage Wp, threshold darkness percentage Bp, and dichroism threshold quality specification value W / B_t 2 0 6 Scan correction table 2 0 8 Calculate threshold dichroism gray quality The value W / B_d 2 1 0 compares the threshold dichroism day quality grayscale value W / B_d with the dichroism image quality threshold specification value W / B_t 2 1 2 Whether B_d

560173 The diagram simply illustrates that the daylight quality threshold specification value is greater than the two-color level W / B_t 2 1 4 increases the daylight quality threshold specification value of the two-color level W / B_t 2 16 decreases the color quality threshold specification value of the two-color level W / B_t 2 1 8 Store the dichroic day quality threshold specification value W / B_t page 12

Claims (1)

560173 6. Application scope 1. A method for automatically adjusting the grayscale value of the threshold dichroism image quality. The method of automatically adjusting the grayscale value of the threshold dichroism image quality includes: setting an initial light and dark density, a final light and dark Density, a threshold brightness percentage, a threshold darkness percentage, and a two-color gradation day quality threshold specification value; Sweep a correction table that includes at least one light and dark density region, and the light and dark density region has autonomy The gray level value that continuously changes from dark to full light; calculates a threshold two-color level image quality based on the initial light and dark density, the final light and dark density, the threshold brightness percentage, the threshold darkness percentage, and the scan correction table results Grayscale value; and compare the threshold grayscale value of the threshold two-color image quality with the threshold value of the threshold of the two-daylight quality threshold. The darkest picture is the final color of the order, the second limit and the degree of density. The degree of dynamic lightness from the beginning of the description of the degree of the area is described in the secret 1 on the dark, the Mingwei surrounding the range, the law of decision-making law to apply for the value of the application is as the order 2_ 灰 密 质 义The order of the day is determined by the two-system limit ratio, which is one hundred and one hundred minutes. It is bright and self-limiting. The value of Liangshen, which is specially requested, is as follows: Discrimination of gray and quality. The order of the day is determined by the two series of limit ratios. One hundred points are scheduled to visit Hitachi JiJno. No. 1 in the middle, the law. The dark application value that is specifically requested is as follows: 4. Gray and page 13 560173 6. Application for patent scope 5. As described in item 1 of the scope of patent application, the threshold value of daylight quality gray scale is automatically adjusted. The method, wherein when the threshold dichroic day quality gray scale value is equal to the dichroic day quality threshold value, the dichroic day quality threshold value is stored. 6. The method for automatically adjusting a threshold dichroic diurnal grayscale value as described in item 1 of the scope of patent application, wherein when the threshold dichroic diurnal grayscale value is smaller than the dichroic diurnal grayscale value When the limit specification value is set, the dichroic image quality threshold specification value is increased until the dichroic day quality threshold specification value is equal to the threshold dichroic day quality gray scale value. 7. The method for automatically adjusting the threshold grayscale value of the threshold dichroism image quality as described in item 1 of the scope of patent application, wherein when the threshold grayscale value of the threshold dichroism daylight quality is greater than the threshold of the dichroic daylight quality When the limit specification value is reached, the dichroism threshold quality specification value is reduced until the dichroism day quality threshold specification value is equal to the threshold dichroism picture quality grayscale value. 8. —A method for automatically adjusting the threshold dichroism diurnal grayscale value. The method for automatically adjusting the threshold dichroic diurnal grayscale value includes: setting an initial light and dark density, a final light and dark density, and a threshold. Brightness percentage, one threshold darkness percentage, and one-two-color day quality threshold specifications; Scanning seedlings-correction table, the correction table includes at least one light and dark density region, which has a continuous range from self-dark to full-bright Changed grayscale value; according to the initial light and dark density, the final light and dark density, the threshold brightness 560173 6. Percentage of patent application range, the threshold darkness percentage and the scan correction table result to calculate a threshold two-color daylight grayscale value; compare the threshold two-color image quality grayscale value with the two-color Day quality threshold specification value; and when the threshold two-color day quality gray scale value is smaller than the two-color day quality threshold specification value, increase the two-color day quality threshold specification value until the two-color scale The day quality threshold specification value is equal to the threshold dichroism grayscale value. 9. A method for automatically adjusting the threshold dichroism diurnal grayscale value. The method for automatically adjusting the threshold dichroism diurnal grayscale value includes: setting an initial light and dark density, a final light and dark density, and a threshold brightness. Percentage, a threshold darkness percentage, and a two-color gradation day quality threshold specification value; scan a correction table that includes at least one light and dark density region, which has a continuous change from full dark to full light Grayscale value; calculate a threshold two-color daylight grayscale value based on the initial light and dark density, the final light and dark density, the threshold brightness percentage, the threshold darkness percentage, and the scan correction table results; compare the Threshold grayscale value of the dichroic image quality and the threshold value of the dichroic image quality threshold; and When the threshold dichroic day quality grayscale value is greater than the dichroic day quality threshold specification value, the dichroic image quality threshold specification value is reduced until the dichroic day quality threshold specification value is equal to the threshold. Limited to two-tone grayscale value. Page 15