WO2005001749A1

WO2005001749A1 - Method of enhancing digital image information of two-dimensional bar code

Info

Publication number: WO2005001749A1
Application number: PCT/CN2004/000698
Authority: WO
Inventors: Longxiang Bian
Original assignee: Lp Technologies (Shanghai) Inc.
Priority date: 2003-06-27
Filing date: 2004-06-28
Publication date: 2005-01-06
Also published as: CN1472704A

Abstract

A method for providing enhanced processing to two-dimension bar code digital images along horizontal and vertical directions simultaneously. In the method, digital images is composed of a original pixel matrix of n row x m column, and the method includes following steps: (1) inserting k blank pixels between two adjacent original pixels along horizontal direction of the pixel matrix of n row x m column so as to form a pixel matrix of (k(n-1)+n) row x m column; (2) inserting k' blank pixels between two adjacent pixels along vertical direction of the pixel matrix of (k(n-1)+n) row x m column so as to form a pixel matrix of (k(n-1)+n) row x (k'(m-1)+m) column; (3) for the blank pixel which is inserted between two adjacent original pixels along horizontal direction or vertical direction, the attribute value is obtained by interpolation based the attribute values of two original pixels, for others, their attribute value is obtained by interpolation based the attribute value of the closest (4) original pixels.

Description

Method for enhancing two-dimensional barcode digital image information

The present invention relates to a method for enhancing two-dimensional digital image information, and in particular, to a method for improving resolution of a two-dimensional barcode digital image through interpolation enhancement processing. Background technique

Computers have excellent computing power and storage capacity, but in contrast, data input capabilities cannot match them, which limits the increase in computer processing power. For this reason, people invented bar codes, a graphic symbol system specially designed for easy machine reading.

In order to increase the information capacity of the bar code, several one-dimensional bar codes are initially stacked together to form a stack code. In order to further increase the information storage capacity, the information storage density must be increased. As a result, a two-dimensional bar code that is completely different from the one-dimensional bar code and the stack code in principle and structure was born. Because two-dimensional digital images such as two-dimensional barcodes have high information capacity and information density, higher requirements are also placed on image processing systems. Figure 1 shows an image processing system that reads two-dimensional barcodes. As shown in FIG. 1, the system includes an image intake device 1, an image conversion device 2, an image memory 3, an image processing device 4, and a decoding device 5. First, the image ingesting device 1 converts a two-dimensional barcode image into an electric analog signal, and then the image converting device 2 converts the electric analog signal into a digital signal, and the image memory 3 stores a two-dimensional barcode digital image in the form of a digital signal. The image processing device 4 extracts effective information capable of two-dimensional barcode decoding from the digitized image, and the decoding device 5 decodes the decoded effective information and outputs characters and graphics compiled in the two-dimensional barcode ( (Such as photos, fingerprints, etc.).

In order to meet the requirements of high-capacity and high-density digital image reading, there are basically two methods at present, which will be further described below.

One solution is to increase the resolution of the photoelectric sensor in the image capture device and increase the size of the captured image. However, the resolution of the photoelectric sensor is limited by the process level, and it is very difficult to improve the resolution. Moreover, the system cost also increases greatly with the increase of the resolution.

Another solution is to enhance the digital image in an image processing device. Specifically, the one-dimensional barcode is scanned with a chain code, and then the trajectory is scanned along the chain code to perform interpolation processing on the barcode and the space of the one-dimensional barcode to improve the analysis of the one-dimensional barcode information. Resolution. However, this method is limited to image enhancement processing in one direction, so it is only applicable to digital images such as one-dimensional barcodes, and cannot be applied to the enhancement of digital image information such as two-dimensional barcodes. Summary of the invention

An object of the present invention is to provide a method for enhancing two-dimensional barcode digital image information, which can simultaneously enhance the two-dimensional barcode digital image information in both horizontal and vertical directions.

The object of the present invention is achieved by the following technical solutions:

A method for enhancing two-dimensional barcode digital image information. The digital image is composed of an original pixel matrix of n rows and x m columns. Each original pixel has a certain attribute value and includes the following steps:

(1) inserting k blank pixels between two adjacent original pixels along the horizontal direction of the pixel matrix of n rows by X m columns to form a pixel matrix of (k (n-1) + n) rows by Xm columns;

(2) Insert k 'blank pixels between two adjacent pixels along the vertical direction of the pixel matrix of 0m-1) + n) rows Xm columns to form (k (nl) + n) rows X a pixel matrix of (k '(ml) + m) columns; and

(3) In the (k (nl) + n) row X (k '(ml) + m) column pixel matrix, for a blank pixel inserted between two adjacent original pixels in the horizontal or vertical direction , Its attribute value is obtained by interpolation based on the attribute values of the two original pixels, and for other blank pixels, its attribute value is obtained by interpolation based on the attribute values of the four original pixels nearest to it.

It is better that in the above-mentioned two-dimensional barcode digital image information enhancement method, the attribute value of each pixel is its gray value. Or, the attribute value of each pixel is the intensity value of its three primary colors. Alternatively, the attribute value of each pixel is its fluorescence emission property.

Preferably, in the above-mentioned method for enhancing digital image information of a two-dimensional barcode, the interpolation calculation is performed according to a linear interpolation algorithm. '

The advantage of the above method is that by enlarging the original digital image several times and determining the values of the attributes of the blank pixels by using interpolation algorithms, it is possible to obtain a two-dimensional barcode image with high information capacity and density obtained by a low-resolution and small-image-size image intake device Performing the reading reduces the product cost and improves the correct reading rate of the two-dimensional barcode. This method can be used not only for two-dimensional bar code readers, but also for one-dimensional bar code readers and other two-dimensional digital image processing systems for other purposes. BRIEF DESCRIPTION OF THE DRAWINGS The objectives, features, and advantages of the present invention can be further understood through the following description of the preferred embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 shows an image processing system for reading a two-dimensional barcode.

Figures 2a and 2b are schematic diagrams of the original digital image and the mapped digital image of the two-dimensional barcode, respectively. detailed description

The two-dimensional barcode digital image information before the enhancement processing can actually be regarded as a dot matrix composed of a plurality of pixels arranged in a matrix form. Each pixel is located on one of the matrix points and has a certain attribute value. The attribute value here It can be an optical property such as the gray value of the pixel, the intensity value of the three primary colors, or the fluorescence emission property.

The core idea of the method of the present invention is that, in order to improve the resolution, first of all, the original digital image (that is, the two-dimensional barcode digital image before the enhancement processing described above, and the pixels in the digital image are hereinafter referred to as original pixels) are horizontal and vertical Direction enlargement, specifically, taking a pixel matrix of n rows by m columns as an example, the operation mode is to insert k blank pixels between two adjacent original pixels along the horizontal direction of the matrix to form (k (nl) + n) i Xm column pixel matrix, and along the vertical direction of the (k (nl) + n) row Xm column pixel matrix, insert k 'blank pixels between two adjacent pixels to form (k (nl ) + n) mapped pixel matrix of row X (k '(ml) + m) column. Then, the attribute value of the blank pixel is interpolated according to the attribute value of the original pixel. Specifically, the pixel is mapped in the enlarged (k (nl) + n) row X (k '(ml) + m) column. In the matrix, blank pixels inserted between two adjacent original pixels in the horizontal or vertical direction can be calculated by interpolation according to the attribute values of these two original pixels. For other blank pixels, The attribute values of the neighboring 4 original pixels are calculated by interpolation. In the above interpolation calculation, it is assumed that the attribute value of each blank pixel is related to the attribute value of the neighboring original pixel, so the attribute value of each blank pixel is the product of its neighboring original pixel attribute value and the corresponding correlation degree. Sum, ie

N

Ρ '^ Ρ ^ η ^ Ν (1)

Here P 'is the attribute value of a blank pixel, Pi is the attribute value of the blank pixel adjacent to the original pixel, N is the number of primitive pixels adjacent to the blank pixel, and Tii is the number of neighboring original pixels and the blank pixel. Relevance. The correlation between each pair of neighboring pixels and the value of the blank pixel attribute is related to the spatial distance between them. Off, when this correlation degree has a linear relationship with distance, it is called linear interpolation, and if it is non-linear, it is called nonlinear interpolation. It is easy to understand that when a pixel is an area composed of multiple points, the spatial distance between pixels is the distance between specific position points in the multi-point area.

A preferred embodiment of the enhancement processing method according to the present invention is described below. Assume that the two-dimensional barcode digital image information before processing is composed of a pixel matrix of n rows by m columns, and its attribute value is the gray value of the pixel. For simplicity, it is horizontally between two adjacent original pixels. Only one blank pixel is inserted, and only one blank pixel is inserted between two adjacent pixels in the vertical direction.

The first is the enlargement mapping or interpolation processing steps of the original pixel matrix. To this end, the original digital image area of the two-dimensional barcode should be mapped to another mapping area larger than the original digital image area, that is, a digital image area composed of a pixel matrix of (211-1 :) rows X (2m-1) columns .

As shown in FIG. 2a, in the original digital image area, each pixel can be represented by an array (i, j), and Pi, j can be used to represent the gray value of the pixel, where i is the horizontal coordinate, which represents that the pixel is horizontal. Sequence number in the direction (assuming from left to right), and (nl) ≥i≥0, j is the vertical coordinate, which represents the sequence number of the pixel in the vertical direction (assuming from top to bottom), and (ml) ≥j≥ 0.

As shown in FIG. 2b, in the mapped digital image area, each pixel is represented by an array (i ', j') and its position is represented by P'i ,, j, where i is the horizontal Coordinate, represents the serial number of the pixel in the horizontal direction (assuming from left to right), and (2n-2) ≥i, ≥l, j, is a vertical coordinate, represents the serial number of the pixel in the vertical direction (assuming from above) To the next), and (2m-2) ≥j'≥l.

For the original pixel, its coordinates in the mapped digital image area and its coordinates in the original digital image area satisfy the following relationship-i '= 2i (2a)

j '= 2j (2b) Therefore, the mapping relationship between the gray value of the original pixel between the two digital image regions is:

Then, the blank pixels in the mapped digital image area are interpolated. As shown in FIG. 2b, in the mapped digital image area, each original pixel point corresponds to three blank pixel points adjacent to it, They are located to the right, lower, and lower right of their immediate neighbors. Taking the original pixel with coordinates (i ,, j,) as an example, the coordinates of three adjacent corresponding blank pixels are (i, + l, j,), (i, j '+ l,) And (i '+ l, j, + l). According to the above interpolation calculation method, for the blank pixels located on the right and below, since they are respectively located between two adjacent original pixels (i ', j') and (i '+ 2, j') and (i ' , j ') and (^' + 2), so the gray value can be obtained by interpolation calculation according to the gray value of two adjacent original pixels and the correlation between the original pixel and the blank pixel. For the blank pixel at the bottom right, its 4 original pixels (i'j '), (i, + 2, j,), (i ,, j, + 2) and (i' + 2, j '+ 2 ) Is the nearest neighbor, so the gray value can be obtained by interpolation calculation based on the gray values of the four adjacent original pixels and the correlation between the original pixels and the blank pixels.

The most commonly used interpolation algorithm is a linear interpolation processing algorithm, which assumes that the correlation between the original pixel and the blank pixel is linear with the spatial distance between them. If a linear interpolation algorithm is used in this embodiment, the gray values of the three blank pixels can be expressed by the following formula:

P ₊ u '= (P j- + P ₊₂ j 2 (4a)

^ _{+ ϊ} = Ρ ^ ₊₂ ) / 2 (4b)

For all blank pixel points in the mapped digital image area, the above formula can be used to calculate the corresponding gray value according to the gray value interpolation of neighboring original pixels, thereby obtaining a mapped digital image area with enhanced resolution.

It is worth pointing out that the linear interpolation algorithm is used in this embodiment, but this does not mean that the present invention cannot use other non-linear algorithms. In fact, what kind of interpolation enhancement processing algorithm is used depends on the specific application environment. The core idea of the invention has nothing to do with it. In addition, in this embodiment, although a blank pixel is inserted between two adjacent pixels in the horizontal direction and the vertical direction, this is only an assumption made for understanding and description convenience. In fact, After reading the above description of the description, a person of ordinary skill in the art can easily generalize the principle of the present invention to a situation in which multiple blank pixels are inserted between adjacent pixels and the number of blank pixels is different in both directions.

Claims

Rights request

A method for enhancing digital image information of a two-dimensional barcode, the digital image is composed of an original pixel matrix of n rows and Xm columns, and each original pixel has a certain attribute value, and is characterized by comprising the following steps:

(1) along the horizontal direction of the pixel matrix of n rows by X m columns, inserting k blank pixels between two adjacent original pixels to form a pixel matrix of (k (nl) + n) rows by X m columns;

(2) Insert k ′ blank pixels between two adjacent pixels along the vertical direction of the pixel matrix of (k (nl) + n) rows and Xm columns to form (k (nl) + n) rows X a pixel matrix of (k '(ml) + m) columns; and

(3) In the pixel matrix of (k (n-1) + n) rows X (k '(m-1) + m) columns, for inserting between two adjacent original pixels in the horizontal or vertical direction For blank pixels, the attribute values are calculated by interpolation based on the attribute values of the two original pixels. For other blank pixels, the attribute values are calculated based on the attributes of the 4 original pixels closest to them. get.

2. The method for enhancing digital image information of a two-dimensional barcode according to claim 1, wherein the attribute value of each pixel is its gray value.

The method for enhancing digital image information of a two-dimensional barcode according to claim 1, wherein the attribute value of each pixel is the intensity value of its three primary colors.

4. The method for enhancing digital image information of a two-dimensional barcode according to claim 1, wherein the attribute value of each pixel is its fluorescence emission property.

The method for enhancing two-dimensional barcode digital image information according to any one of claims 1 to 4, wherein the interpolation calculation is performed according to a linear interpolation algorithm.