CN109727232B - Method and apparatus for detecting dot area ratio of printing plate - Google Patents

Abstract

The invention discloses a method and a device for detecting the dot area rate of a printing plate, wherein the method comprises the following steps: collecting a dot image of a printing plate; carrying out graying processing on the dot image to generate a grayscale image; binarizing the gray level image to generate a binarized image; filtering the binary image to generate a filtered image; and calculating the ratio of the number of the pixels representing the dots in the filtered image to the total number of the pixels in the filtered image to obtain the dot area rate of the printing plate. The invention reduces the complexity of the detection of the area rate of the printing dots of the printing plate, improves the detection speed and saves the time. In addition, the invention is beneficial to the miniaturization and the portability of the detection system of the dot area rate, and can be conveniently applied to the field proofing and verification of a flexographic printing system.

Description

Method and equipment for detecting dot area ratio of printing plate

technical field

The invention belongs to the technical field of detecting the dot area ratio of printing plates, and in particular relates to a method and equipment for detecting the dot area ratio of printing plates.

Background technique

At present, in the process of calculating the dot area ratio of the printing plate, a camera is often used to collect the dot image of the printing plate, and then the dot image is transmitted to a large workstation for calculation. Due to the large size of large workstations, inconvenient operation, complex calculations, and high cost, this solution is difficult to apply to on-site proofing and verification of flexographic printing systems, and the dot area ratio of printing plates cannot be given in real time.

Contents of the invention

The technical problem to be solved by the embodiments of the present invention is to provide a method and equipment for detecting the dot area ratio of the printing plate in order to overcome the defects of high calculation cost and inconvenient operation of the dot area ratio of the printing plate in the prior art.

Embodiments of the present invention solve the above-mentioned technical problems through the following technical solutions:

The embodiment of the present invention provides a method for detecting the dot area ratio of a printing plate, comprising the following steps:

S1, collecting the dot image of the printing plate;

S2. Perform grayscale processing on the dot image to generate a grayscale image;

S3. Binarize the grayscale image to generate a binarized image;

S4. Filtering the binarized image to generate a filtered image;

S5. Calculate the ratio of the number of pixels representing dots in the filtered image to the total number of pixels in the filtered image to obtain the dot area ratio of the printing plate.

Preferably, the dot image is an RGB color image, and step S2 includes:

Perform grayscale processing on each pixel of the dot image according to the following formula,

f=[0.395×R+0.641×G+0.234×B+0.5], wherein, f is the gray value of the pixel, R is the brightness value of the red channel of the pixel, G is the brightness value of the green channel of the pixel, and B is The brightness value of the pixel's blue channel.

Preferably, step S3 includes:

The grayscale image was binarized using the Otsu method.

Preferably, step S4 includes:

Each pixel of the binarized image is processed in sequence from left to right and from top to bottom as follows:

Replace the value of the pixel with the correction value, and the correction value is the value obtained by the difference or the value of all the pixels adjacent to the pixel in the binarized image; the pixel adjacent to the pixel is the adjacent left side of the pixel, Pixels to the right, top, and bottom.

Preferably, the pixels representing the dots are pixels with a value of 1.

Preferably, between step S4 and step S5, the method further includes the following steps:

Calculate the number of pixels with a value of 1 in each row of pixels of the filtered image Ni, i∈[1,r], where r is the number of rows of pixels in the filtered image; if the value of the first row of the filtered image is 1 The number of pixels N1 is greater than 0 and less than or equal to Nj, j∈[2,r-1], then delete the first line; if the number of pixels with a value of 1 in the last line of the filtered image Nr is greater than 0 and less than or equal to Nj , j∈[2,r-1], delete the last row;

Calculate the number Mk of pixels with a value of 1 in each column of pixels of the filtered image, k ∈ [1, c], where c is the number of l columns of pixels in the filtered image; if the value of the first column of the filtered image is The number of pixels M1 of 1 is greater than 0 and less than or equal to Mn, n∈[2,c-1], then delete the first column; if the number of pixels Mc with a value of 1 in the last column of the filtered image is greater than 0 and less than or equal to Mn, n∈[2,c-1], delete the last column;

Output the cropped image;

Step S5 further includes: calculating the percentage of the number of pixels with a value of 1 in the cropped image to the total number of pixels in the cropped image, and using the percentage as the dot area ratio of the printing plate.

The present invention also provides a portable dot area ratio detection device, including a portable housing, an image acquisition unit, a grayscale processing unit, a binarization unit, a filter unit, and a dot area ratio calculation unit;

The image acquisition unit is arranged on the portable housing, and the grayscale processing unit, binarization unit, filter unit, and dot area ratio calculation unit are arranged inside the portable housing;

The image acquisition unit is used to acquire the dot image of the printing plate;

The grayscale processing unit is used to grayscale the dot image to generate a grayscale image;

The binarization unit is used to binarize the grayscale image to generate a binarized image;

The filtering unit is used to filter the binarized image to generate a filtered image;

The dot area ratio calculation unit is used to calculate the ratio of the number of pixels representing dots in the filtered image to the total number of pixels in the filtered image to obtain the dot area ratio of the printing plate.

Preferably, the detection device further includes a display unit, the display unit is arranged on the outer surface of the portable casing, and the display unit is used to display the dot area ratio of the printing plate.

Preferably, the image acquisition unit includes a CMOS (Complementary Metal Oxide Semiconductor, Complementary Metal Oxide Semiconductor) image sensor, and the resolution of the CMOS image sensor is 5 million pixels to 25 million pixels.

Preferably, the detection device further includes a cutting unit, and the cutting unit is arranged inside the portable casing;

The grayscale processing unit is also used to grayscale each pixel of the dot image according to the following formula:

f=[0.395×R+0.641×G+0.234×B+0.5], wherein, f is the gray value of the pixel, R is the brightness value of the red channel of the pixel, G is the brightness value of the green channel of the pixel, and B is the luminance value of the blue channel of the pixel;

The binarization unit is also used to binarize the grayscale image by the Otsu method;

The filtering unit is also used to process each pixel of the binarized image sequentially from left to right and from top to bottom: replace the value of the pixel with a correction value, and the correction value is all The value of the pixel adjacent to the pixel is different or the value obtained; the pixel adjacent to the pixel is the pixel adjacent to the left, right, upper, and lower sides of the pixel;

The cropping unit is used to calculate the number of pixels with a value of 1 in each row of pixels of the filtered image Ni, i∈[1,r], where r is the number of rows of pixels in the filtered image; if the first row of the filtered image The number of pixels with a value of 1 N1 is greater than 0 and less than or equal to Nj, j∈[2,r-1], then delete the first row; if the number of pixels with a value of 1 in the last row of the filtered image Nr is greater than 0 And less than or equal to Nj, j∈[2,r-1], delete the last row;

The clipping unit is also used to calculate the number Mk of pixels with a value of 1 in each column of pixels of the filtered image, k ∈ [1, c], where c is the number of l columns of pixels in the filtered image; The number M1 of pixels with a value of 1 in a column is greater than 0 and less than or equal to Mn, n∈[2,c-1], then delete the first column; if the number of pixels with a value of 1 in the last column of the filtered image Mc Greater than 0 and less than or equal to Mn, n∈[2,c-1], delete the last column;

The cropping unit is also used to output the cropped image;

The dot area ratio calculation unit is also used to calculate the percentage of the number of pixels with a value of 1 in the cropped image to the total number of pixels in the cropped image, and use the percentage as the dot area ratio of the printing plate.

The positive progress effect of the present invention lies in: the present invention reduces the detection complexity of the dot area ratio of the printing plate, improves the detection speed, and saves time. Moreover, the invention is beneficial to the miniaturization and portability of the detection system of the dot area ratio, and can be conveniently applied to on-site proofing and verification of a flexographic printing system.

Description of drawings

FIG. 1 is a schematic structural diagram of a portable dot area ratio detection device according to Embodiment 1 of the present invention.

Fig. 2 is a schematic diagram of the processing of pixels in the first row and first column by the filter unit of the portable dot area ratio detection device according to Embodiment 1 of the present invention.

Fig. 3 is a schematic diagram of processing pixels in the first row and the second column by the filter unit of the portable dot area ratio detection device according to Embodiment 1 of the present invention.

FIG. 4 is a flow chart of a method for detecting the dot area ratio of the printing plate according to Embodiment 1 of the present invention.

FIG. 5 is a schematic structural diagram of a portable dot area ratio detection device according to Embodiment 2 of the present invention.

FIG. 6 is a flow chart of a method for detecting the dot area ratio of a printing plate according to Embodiment 2 of the present invention.

Detailed ways

The present invention is further illustrated below by means of examples, but the present invention is not limited to the scope of the examples.

Example 1

The present embodiment provides a detection device of a portable dot area ratio. With reference to FIG. 103 , a filter unit 104 , and a dot area ratio calculation unit 105 . The image acquisition unit 101 is arranged on the portable housing, and the grayscale processing unit 102, the binarization unit 103, the filtering unit 104, and the dot area ratio calculation unit 105 are arranged inside the portable housing.

The image acquisition unit 101 is used to acquire the dot image of the printing plate. The grayscale processing unit 102 is configured to perform grayscale processing on the dot image to generate a grayscale image. The binarization unit 103 is used to binarize the grayscale image to generate a binarized image. The filtering unit 104 is used for filtering the binarized image to generate a filtered image. The dot area ratio calculation unit 105 is used to calculate the ratio of the number of pixels representing dots in the filtered image to the total number of pixels in the filtered image to obtain the dot area ratio of the printing plate.

When using the portable dot area ratio detection device of this embodiment, the user can hold the detection device to perform on-site proofing of the flexographic printing system, and the image acquisition unit 101 collects the dot image of the printing plate. In this embodiment, the image acquisition unit adopts a CMOS image sensor, and the resolution of the CMOS image sensor is 10 million pixels. In other optional implementation manners, the image acquisition unit may use a CCD (Charge Coupled Device) image sensor, and the resolution of the image acquisition unit preferably ranges from 5 million pixels to 25 million pixels.

Then, the grayscale processing unit 102 performs grayscale processing on the halftone dot image. In this embodiment, the grayscale processing unit 102 performs grayscale processing on each pixel of the dot image according to the following formula:

f=[0.395×R+0.641×G+0.234×B+0.5], wherein, f is the gray value of the pixel, R is the brightness value of the red channel of the pixel, G is the brightness value of the green channel of the pixel, and B is The brightness value of the pixel's blue channel. The grayscale processing method can improve the accuracy of subsequent processing. After grayscale processing, a grayscale image is obtained.

Next, the binarization unit 103 binarizes the grayscale image to generate a binarized image. In this embodiment, the binarization unit 103 uses the Otsu method to binarize the grayscale image. Each pixel in the grayscale image has a grayscale value f, that is, its grayscale is f (according to f, a picture can be divided into foreground point pixels and background point pixels. Foreground point pixels refer to all gray levels below or equal to The pixel point of t*, the background point pixel refers to the pixel point greater than t*, t* is the binary segmentation threshold of foreground and background). The proportion of the foreground pixel to the total grayscale image can be recorded as w0, the average value of the foreground pixel’s pixel value can be recorded as u0, the proportion of the background pixel to the total grayscale image can be recorded as w1, and the pixel value of the background pixel can be The mean value of is denoted as u1. Then the mean value of the pixels of the entire grayscale image is recorded as u=w0*u0+w1*u1. Construct the objective function g(t)=w0*(u0-u)^2+w1*(u1-u)^2. Calculate g(t), and when g(t) is the maximum, the corresponding t can be determined as the binarized segmentation threshold t*. In the grayscale image, the value of the pixel whose grayscale value is greater than the binarization segmentation threshold t* is marked as 1, and the value of the pixel whose grayscale value is not greater than the binarization segmentation threshold t* in the grayscale image is marked as 0, so that the binary Value image. After binarization processing, each pixel only needs one binary number to represent, which greatly reduces the amount of computation for subsequent processing.

Then, the filtering unit 104 filters the binarized image to generate a filtered image. In this embodiment, the filtering unit 104 sequentially processes each pixel of the binarized image from left to right and from top to bottom as follows: replace the value of the pixel with a correction value, and the correction value is binarized The values of all the pixels adjacent to the pixel in the image are different or obtained; the pixels adjacent to the pixel are the pixels adjacent to the left, right, upper, and lower sides of the pixel. Fig. 2 shows some pixels in the upper left corner of the binarized image. When filtering, the first pixel P1 in the first row and first column of the binarized image is first processed, there are no pixels on the left and upper sides of the first pixel P1, and the adjacent pixels of the first pixel P1 are on the right side The second pixel P2 and the third pixel P3 below it. The pixel value 0 of the second pixel P2 is exclusive ORed with the pixel value 1 of the third pixel P3 to obtain 1, then as shown in FIG. 3 , the value of the first pixel P1 is replaced with 1. Then, the next pixel, the second pixel P2, is processed. The adjacent pixels of the second pixel P2 are the first pixel P1 on the left, the fourth pixel P4 on the right, and the fifth pixel P5 on the lower side. The value remains unchanged at 0. Then, the fourth pixel P4 is processed. When the last pixel of the first row is processed, the first pixel of the second row (third pixel P3) is processed. And so on, until all the pixels of the binarized image are processed, and the filtered image is obtained. After filtering, the noise in the binarized image is removed, which can improve the detection accuracy of the dot area ratio.

Next, the dot area ratio calculation unit 105 counts the number of pixels representing dots (i.e., pixels with a value of 1) in the filtered image and the total number of pixels in the filtered image, and calculates the percentage of the former accounting for the latter, which is is the dot area ratio of the printing plate.

The portable dot area ratio detection device of this embodiment reduces the complexity of the detection of the dot area ratio of the printing plate, improves the detection speed, and saves time. And, because the computational complexity is reduced, the grayscale processing unit, binarization unit, filtering unit, and dot area ratio calculation unit of this embodiment can be integrated in one CPU (central processing unit), thereby realizing miniaturization and portable The design can be easily applied to flexographic printing system on-site proofing and verification.

Present embodiment also provides a kind of detection method of the dot area ratio of printing plate, this detection method adopts the detection equipment of portable dot area ratio of the present embodiment to realize, with reference to Fig. 4, this detection method comprises the following steps:

Step S201, collecting the dot image of the printing plate;

Step S202, performing grayscale processing on the dot image to generate a grayscale image;

Step S203, binarize the grayscale image to generate a binarized image;

Step S204, filtering the binarized image to generate a filtered image;

Step S205 , calculating the ratio of the number of pixels representing dots in the filtered image to the total number of pixels in the filtered image to obtain the dot area ratio of the printing plate.

In step S201 , the dot image of the printing plate is captured by the image capture unit 101 .

In step S202, the grayscale processing unit 102 performs grayscale processing on each pixel of the dot image according to the following formula:

f=[0.395×R+0.641×G+0.234×B+0.5], wherein, f is the gray value of the pixel, R is the brightness value of the red channel of the pixel, G is the brightness value of the green channel of the pixel, and B is The brightness value of the pixel's blue channel. The grayscale processing method can improve the accuracy of subsequent processing. After grayscale processing, a grayscale image is obtained.

In step S203, the binarization unit 103 binarizes the grayscale image using the Otsu method. Each pixel in the grayscale image has a grayscale value f, that is, its grayscale is f (according to f, a picture can be divided into foreground point pixels and background point pixels. Foreground point pixels refer to all gray levels below or equal to The pixel point of t*, the background point pixel refers to the pixel point greater than t*, t* is the binary segmentation threshold of foreground and background). The proportion of the foreground pixel to the total grayscale image can be recorded as w0, the average value of the foreground pixel’s pixel value can be recorded as u0, the proportion of the background pixel to the total grayscale image can be recorded as w1, and the pixel value of the background pixel can be The mean value of is denoted as u1. Then the mean value of the pixels of the entire grayscale image is recorded as u=w0*u0+w1*u1. Construct the objective function g(t)=w0*(u0-u)^2+w1*(u1-u)^2. Calculate g(t), and when g(t) is the maximum, the corresponding t can be determined as the binarized segmentation threshold t*. In the grayscale image, the value of the pixel whose grayscale value is greater than the binarization segmentation threshold t* is marked as 1, and the value of the pixel whose grayscale value is not greater than the binarization segmentation threshold t* in the grayscale image is marked as 0, so that the binary Value image. After binarization processing, each pixel only needs one binary number to represent, which greatly reduces the amount of computation for subsequent processing.

In step S204, the filtering unit 104 performs the following processing on each pixel of the binarized image sequentially from left to right and from top to bottom: replace the value of the pixel with a correction value, and the correction value is the binary image The values of all the pixels adjacent to the pixel in are different or the obtained value; the pixels adjacent to the pixel are the pixels adjacent to the left, right, upper, and lower sides of the pixel. Fig. 2 shows some pixels in the upper left corner of the binarized image. When filtering, the first pixel P1 in the first row and first column of the binarized image is first processed, there are no pixels on the left and upper sides of the first pixel P1, and the adjacent pixels of the first pixel P1 are on the right side The second pixel P2 and the third pixel P3 below it. The pixel value 0 of the second pixel P2 is exclusive ORed with the pixel value 1 of the third pixel P3 to obtain 1, then as shown in FIG. 3 , the value of the first pixel P1 is replaced with 1. Then, the next pixel, the second pixel P2, is processed. The adjacent pixels of the second pixel P2 are the first pixel P1 on the left, the fourth pixel P4 on the right, and the fifth pixel P5 on the lower side. The value remains unchanged at 0. Then, the fourth pixel P4 is processed. When the last pixel of the first row is processed, the first pixel of the second row (third pixel P3) is processed. And so on, until all the pixels of the binarized image are processed, and the filtered image is obtained. After filtering, the noise in the binarized image is removed, which can improve the detection accuracy of the dot area ratio.

In step S205, the network dot area ratio calculation unit 105 counts the number of pixels representing network dots (i.e., pixels with a value of 1) in the filtered image and the total number of pixels in the filtered image, and calculates the percentage of the former accounting for the latter, the The percentage is the dot area ratio of the printing plate.

Example 2

On the basis of the detection device for the portable dot area ratio in embodiment 1, this embodiment provides a portable dot area ratio detection device. Referring to FIG. 2 , the detection device further includes a cutting unit 106 and a display unit 107 . The cutting unit 106 is disposed inside the portable housing, and the display unit 107 is disposed on the outer surface of the portable housing. The display unit 107 is used to display the dot area ratio of the printing plate.

Cutting unit 106 is used for calculating the quantity Ni of the pixel that value is 1 in each row of pixels of the filtered image, i∈[1, r], wherein r is the row number of the pixel of the filtered image; if the first filtered image The number N1 of pixels with a value of 1 in the row is greater than 0 and less than or equal to Nj, j∈[2,r-1], then delete the first row; if the number of pixels with a value of 1 in the last row of the filtered image Nr is greater than 0 and less than or equal to Nj, j∈[2,r-1], delete the last row; the clipping unit is also used to calculate the number of pixels with a value of 1 in each column of the filtered image Mk, k∈[1,c ], where c is the number of l columns of pixels in the filtered image; if the number M1 of pixels whose value is 1 in the first column (the leftmost column) of the filtered image is greater than 0 and less than or equal to Mn, n∈[2, c-1], delete the first column; if the number Mc of pixels with a value of 1 in the last column (the rightmost column) of the filtered image is greater than 0 and less than or equal to Mn, n∈[2,c-1], then delete the last column; the cropping unit is also used to output the cropped image. That is, the cropping unit 106 receives the filtered image output by the filtering unit 104, and calculates the number of pixels with a value of 1 in each row of pixels of the filtered image. The number N1 of pixels whose value is 1 in the first row of the filtered image is not equal to 0, then the number N1 of pixels whose value is 1 in the first row of the filtered image is one by one with other than the first row and the last row The number Nj(j∈[2,r-1]) of pixels with a value of 1 in each row is compared, and if N1 is not greater than the smallest one of Nj(j∈[2,r-1]), then it is determined that the filtered image is above The grid at the edge is incomplete, and the reference value for the detection of the dot area ratio is low, so the first line of the filtered image is deleted. While judging the first row, the cropping unit 106 also judges whether the last row needs to be deleted according to a similar method, and the cropping unit 106 also judges whether the leftmost column and the rightmost column of the filtered image need to be deleted according to the aforementioned method. After the judgment is completed, the cropping unit 106 deletes the rows or columns satisfying the deletion condition in the filtered image, that is, completes the cropping operation on the filtered image, and outputs the cropped image. In other optional implementation manners, the cropping unit can first judge the first row and the last row of the filtered image, and then perform a corresponding deletion operation to obtain an intermediate image; Judge with the rightmost column, perform the corresponding deletion operation, and finally output the cropped image. Alternatively, the cropping unit can first judge the leftmost column and the rightmost column of the filtered image, and then perform corresponding deletion operations to obtain an intermediate image; then the cropping unit judges the first row and the last row of the intermediate image , perform the corresponding deletion operation, and finally output the cropped image.

Then, the dot area ratio calculation unit 105 counts the number of pixels with a value of 1 in the image after cropping and the total number of pixels in the image after cropping, and calculates the number of pixels with a value of 1 in the image after cropping to account for the number of pixels in the image after cropping The percentage of the total quantity, which is used as the dot area ratio of the printing plate. After the cutting operation, the interference of incomplete grids is eliminated, and the dot area ratio of the final printing plate is more accurate.

The display unit 107 displays the dot area ratio of the printing plate, and also displays the dot image of the printing plate for user reference.

On the basis of the detection method of the dot area ratio of the printing plate in embodiment 1, this embodiment also provides a detection method of the dot area ratio of the printing plate, the detection method adopts the detection device of the portable dot area ratio of the present embodiment Realize, with reference to Fig. 6, this detection method comprises the following steps:

Step S201, collecting the dot image of the printing plate.

Step S202, performing grayscale processing on the dot image to generate a grayscale image.

Step S203, binarize the grayscale image to generate a binarized image.

Step S204, filter the binarized image to generate a filtered image.

Step S2041 , judging whether the edge of the filtered image meets the deletion condition, if so, delete it, and output the cropped image.

Step S205 includes step S2051, calculating the percentage of the number of pixels with a value of 1 in the cropped image to the total number of pixels in the cropped image, and using the percentage as the dot area ratio of the printing plate.

Step S206, displaying the dot area ratio of the printing plate.

During specific implementation, in step S2041, the clipping unit 106 calculates the number Ni of pixels with a value of 1 in each row of pixels of the filtered image, i∈[1, r], where r is the number of rows of pixels in the filtered image; If the number N1 of pixels whose value is 1 in the first line of the filtered image is greater than 0 and less than or equal to Nj, j∈[2,r-1], then delete the first line; if the value of the last line of the filtered image is The number of pixels Nr of 1 is greater than 0 and less than or equal to Nj, j∈[2,r-1], then delete the last row; the cropping unit is also used to calculate the number of pixels with a value of 1 in each column of pixels of the filtered image Mk , k∈[1,c], where c is the l column number of pixels in the filtered image; if the number M1 of pixels whose value is 1 in the first column of the filtered image is greater than 0 and less than or equal to Mn, n∈[2 , c-1], then delete the first column; if the number Mc of pixels with a value of 1 in the last column of the filtered image is greater than 0 and less than or equal to Mn, n∈[2,c-1], then delete the last column; The cropping unit is also used to output cropped images. That is, the cropping unit 106 receives the filtered image output by the filtering unit 104, and calculates the number of pixels with a value of 1 in each row of pixels of the filtered image. The number N1 of pixels whose value is 1 in the first row of the filtered image is not equal to 0, then the number N1 of pixels whose value is 1 in the first row of the filtered image is one by one with other than the first row and the last row The number Nj(j∈[2,r-1]) of pixels with a value of 1 in each row is compared, and if N1 is not greater than the smallest one of Nj(j∈[2,r-1]), then it is determined that the filtered image is above The grid at the edge is incomplete, and the reference value for the detection of the dot area ratio is low, so the first line of the filtered image is deleted. While judging the first row, the cropping unit 106 also judges whether the last row needs to be deleted according to a similar method, and the cropping unit 106 also judges whether the leftmost column and the rightmost column of the filtered image need to be deleted according to the aforementioned method. After the judgment is completed, the cropping unit 106 deletes the rows or columns satisfying the deletion condition in the filtered image, that is, completes the cropping operation on the filtered image, and outputs the cropped image. In other optional implementation manners, the cropping unit can first judge the first row and the last row of the filtered image, and then perform a corresponding deletion operation to obtain an intermediate image; Judge with the rightmost column, perform the corresponding deletion operation, and finally output the cropped image. Alternatively, the cropping unit can first judge the leftmost column and the rightmost column of the filtered image, and then perform a corresponding deletion operation to obtain an intermediate image; then the cropping unit judges the first row and the last row of the intermediate image , perform the corresponding deletion operation, and finally output the cropped image.

Then, in step S2051, the dot area ratio calculation unit 105 counts the number of pixels with a value of 1 in the cropped image and the total number of pixels in the cropped image, and calculates the percentage of the number of pixels with a value of 1 in the cropped image to account for the cropped image. The percentage of the total number of pixels in the post image, which is used as the dot area ratio of the printing plate. After the cutting operation, the interference of incomplete grids is eliminated, and the dot area ratio of the final printing plate is more accurate.

Finally, in step S206, the display unit 107 displays the dot area ratio of the printing plate, and also displays the dot image of the printing plate for user reference.

Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and the protection scope of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principle and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims (8)

1. a detection method of the dot area ratio of printing plate, is characterized in that, comprises the following steps: S1. Collecting the dot image of the printing plate; S2. Perform grayscale processing on the dot image to generate a grayscale image; S3. Binarize the grayscale image to generate a binarized image; S4. Filter the binarized image to generate a filtered image; S5. Calculate the ratio of the number of pixels representing dots in the filtered image to the total number of pixels in the filtered image to obtain the dot area ratio of the printing plate; Step S4 includes: Each pixel of the binarized image is processed as follows in order from left to right and from top to bottom: The value of the pixel is replaced with a correction value, and the correction value is the value obtained from the difference or the obtained value of all pixels adjacent to the pixel in the binarized image; The pixels are adjacent left, right, upper and lower pixels of the pixel; Between step S4 and step S5, the method also includes the following steps: Calculate the number Ni of pixels with a value of 1 in each row of pixels of the filtered image, i∈[1, r], where r is the number of rows of pixels in the filtered image; if the first filtered image The number N1 of pixels with a value of 1 in one line is greater than 0 and less than or equal to Nj, j∈[2, r-1], then delete the first line; if the value of the last line of the filtered image is 1 The number Nr of pixels is greater than 0 and less than or equal to Nj, j∈[2,r-1], then delete the last row; Calculate the number Mk of pixels with a value of 1 in each column of pixels of the filtered image, k∈[1, c], where c is the column number of pixels in the filtered image; if the filtered image's first The number M1 of pixels with a value of 1 in a column is greater than 0 and less than or equal to Mn, n∈[2, c-1], then delete the first column; if the value of the last column of the filtered image is 1 The number of pixels Mc is greater than 0 and less than or equal to Mn, n∈[2,c-1], then delete the last column; Output the cropped image; Step S5 further includes: calculating the percentage of the number of pixels with a value of 1 in the cropped image to the total number of pixels in the cropped image, and using the percentage as the dot area ratio of the printing plate. 2. the detection method of the dot area ratio of printing plate as claimed in claim 1, is characterized in that, described dot image is RGB color image, and step S2 comprises: Each pixel of the dot image is grayscaled according to the following formula, f=[0.395×R+0.641×G+0.234×B+0.5], wherein, f is the gray value of the pixel, R is the brightness value of the red channel of the pixel, and G is the green channel of the pixel is the brightness value of the pixel, and B is the brightness value of the blue channel of the pixel. 3. the detection method of the dot area ratio of printing plate as claimed in claim 1, is characterized in that, step S3 comprises: The grayscale image was binarized by the Otsu method. 4. The detection method of the dot area ratio of the printing plate as claimed in claim 1, wherein the pixel representing the dot is a pixel with a value of 1. 5. A detection device for a portable dot area ratio, characterized in that it includes a portable housing, an image acquisition unit, a grayscale processing unit, a binarization unit, a filter unit, and a dot area ratio calculation unit; The image acquisition unit is arranged on the portable casing, and the grayscale processing unit, the binarization unit, the filtering unit, and the dot area ratio calculation unit are arranged inside the portable casing ; The image acquisition unit is used to acquire the dot image of the printing plate; The grayscale processing unit is used to perform grayscale processing on the dot image to generate a grayscale image; The binarization unit is used to binarize the grayscale image to generate a binarized image; The filtering unit is used to filter the binarized image to generate a filtered image; The dot area ratio calculation unit is used to calculate the ratio of the number of pixels representing dots in the filtered image to the total number of pixels in the filtered image to obtain the dot area ratio of the printing plate; The detection device also includes a cutting unit, the cutting unit is arranged inside the portable housing; The filtering unit is further configured to perform the following processing on each pixel of the binarized image sequentially from left to right and from top to bottom: replace the value of the pixel with a correction value, and the correction value In the binarized image, the values of all pixels adjacent to the pixel are different or obtained; the pixels adjacent to the pixel are the adjacent left, right, and Pixels on the upper and lower sides; The cropping unit is used to calculate the number Ni of pixels with a value of 1 in each row of pixels of the filtered image, i∈[1,r], where r is the number of rows of pixels in the filtered image; if The number N1 of pixels whose value is 1 in the first row of the filtered image is greater than 0 and less than or equal to Nj, j∈[2, r-1], then delete the first row; if the last row of the filtered image The number Nr of pixels with a value of 1 in one row is greater than 0 and less than or equal to Nj, j∈[2, r-1], then delete the last row; The cropping unit is also used to calculate the number Mk of pixels with a value of 1 in each column of pixels of the filtered image, k ∈ [1, c], where c is the number of columns of pixels in the filtered image; if The number M1 of pixels whose value is 1 in the first column of the filtered image is greater than 0 and less than or equal to Mn, n∈[2,c-1], then delete the first column; if the filtered image The number Mc of pixels whose value is 1 in the last column is greater than 0 and less than or equal to Mn, n∈[2,c-1], then delete the last column; The cropping unit is also used to output the cropped image; The dot area ratio calculation unit is also used to calculate the percentage of the number of pixels whose value is 1 in the cropped image to the total number of pixels in the cropped image, and use the percentage as the dot area of the printing plate Rate. 6. the detection equipment of portable dot area ratio as claimed in claim 5, is characterized in that, described detection equipment also comprises display unit, and described display unit is arranged on the outer surface of described portable housing, and described display unit is used for Displays the dot area ratio of the printing plate. 7. The portable dot area ratio detection device according to claim 5, wherein the image acquisition unit comprises a CMOS image sensor, and the resolution of the CMOS image sensor is 5 million pixels to 25 million pixels. 8. the detection equipment of portable network dot area ratio as claimed in claim 5, is characterized in that, described grayscale processing unit is also used for carrying out grayscale processing to each pixel of described network dot image according to following formula: f=[0.395×R+0.641×G+0.234×B+0.5], wherein, f is the gray value of the pixel, R is the brightness value of the red channel of the pixel, and G is the green channel of the pixel The brightness value of B is the brightness value of the blue channel of the pixel; The binarization unit is also used to binarize the grayscale image by Otsu method.

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