CN101908126A - PDF417 barcode decoding chip - Google Patents

Abstract

The invention provides a PDF417 barcode decoding chip, comprising: a scanning module, which generates scanning coordinates; a boundary recognition module, which reads a barcode image according to the scanning coordinates, and calculates the pixels of the read image, so as to obtain the bar space of the barcode image Boundary point; direction identification module, calculate and obtain the barcode direction according to the bar-space boundary point obtained by the boundary recognition module; bar-space boundary processing module, process the barcode image according to the barcode direction, to obtain the bar-space boundary in the barcode image; symbol parameter identification The module identifies the symbol parameters of the barcode according to the bar-space boundary to obtain the symbol parameters; the symbol character acquisition module calculates and obtains the symbol characters according to the bar-space boundary and the symbol parameters; and the decoding module converts the symbol characters into barcode information. The PDF417 barcode decoding chip of the present invention adopts a hardware pipeline structure, is suitable for pipeline operation and parallel processing of barcode images, and has fast processing speed.

Description

PDF417 barcode decoding chip

【Technical field】

The invention relates to the technical field of barcode identification, in particular to a PDF417 barcode decoding chip.

【Background technique】

Bar code technology is an emerging technology developed on the basis of computer technology and information technology that integrates coding, printing, identification, data collection and processing. Barcode technology is widely used in business, library management, warehousing, post and telecommunications, transportation and industrial control due to its advantages of fast, accurate, reliable and low cost, and is bound to play an important role in the emerging "Internet of Things" applications. role.

Currently widely used barcodes include one-dimensional barcodes and two-dimensional barcodes. A one-dimensional barcode, also known as a linear barcode, is composed of multiple "bar" and "space" units arranged in parallel, and the barcode information is expressed by the different widths and positions of the bars and spaces. The two-dimensional barcode is composed of specific black and white geometric figures distributed in the two-dimensional direction according to certain rules, which can express information in the two-dimensional direction. Two-dimensional barcodes can be divided into determinant two-dimensional barcodes and matrix two-dimensional barcodes. Determinant 2D barcodes are stacked by multiple lines of short-cut 1D barcodes. Representative determinant 2D barcodes include PDF417, Code 49, Code 16K, etc. The determinant two-dimensional barcode information representation method is similar to the one-dimensional barcode, and it is also expressed by different widths and positions of bars and spaces. The matrix two-dimensional barcode is composed of black and white modules distributed in the matrix according to predetermined rules. Representative matrix two-dimensional barcodes include QR code, Data Matrix code, Maxi code, Aztec code, Hanxin code, etc.

In the process of decoding barcodes, scanning equipment is usually used to scan barcodes to obtain reflected light signals, or to use photography equipment to photograph barcodes to obtain barcode images, and to identify and process reflected light signals or barcode images to get the barcode information.

As shown in FIG. 1 , it is a Chinese patent application No. 200510126730.7 proposed by Samsung Electronics Co., Ltd., which discloses a method and device for reading barcodes. The device includes: a scanning unit for sensing a barcode and generating a scanning signal; a searching unit for calculating the rate of change of the scanning signal, extracting a slash segment from the scanning signal, and searching the starting point and end point of the extracted slash segment to detect edges of bars of the barcode; and a barcode reading unit for reading the barcode based on the detected distance between the edges. The disadvantage of this method and device for reading barcodes is that the device must rely on the user to correctly sense the direction of the barcode through the scanning unit. The device for reading the barcode itself cannot recognize the direction of the barcode and cannot adjust the decoding direction according to the direction of the barcode. This causes inconvenient use and limitations in application. In the case of high bar-space density or large distortion, the barcode cannot be recognized and decoded.

Therefore, in view of the above deficiencies in the prior art, it is urgent to provide a PDF417 barcode decoding chip, which can ensure the correct recognition of the blank information of the barcode and improve the success rate of decoding.

【Content of invention】

Aiming at the deficiency that the decoding device in the prior art relies on the user to correctly sense the direction of the barcode through the scanning unit, and cannot adjust the decoding direction according to the direction of the barcode, the present invention provides a PDF417 barcode decoding chip, which can correctly identify the blank information of the barcode , to improve the decoding success rate.

The invention provides a PDF417 barcode decoding chip, comprising: a scanning module, which generates scanning coordinates, and the scanning coordinates correspond to the address bits in the address storage space of the data storage, and is used to scan the barcode image in the data storage; a boundary identification module, according to the scanning The coordinates read the barcode image, and calculate the read image pixel points to obtain the bar-space boundary points of the barcode image; the direction recognition module calculates the barcode direction according to the bar-space boundary points obtained by the boundary recognition module; the bar-space boundary The processing module processes the barcode image according to the barcode direction to obtain the bar-space boundary in the barcode image; the symbol parameter identification module identifies the symbol parameter of the barcode according to the bar-space boundary to obtain the symbol parameter; the symbol character acquisition module according to The symbol character is obtained by calculating the bar boundary and the symbol parameter; and the decoding module converts the symbol character into barcode information.

The PDF417 barcode decoding chip of the present invention can automatically identify the direction of the barcode, realize the identification and decoding of the barcode image without the user adjusting the scanning direction of the scanning unit, and has high identification accuracy of the barcode boundary and a high decoding success rate.

The PDF417 barcode decoding chip of the present invention can adjust the decoding direction according to the direction of the barcode, obtain the precise coordinate value of the barcode boundary, greatly improve the decoding success rate, and is especially suitable for the identification and decoding of high-density barcodes or distorted barcodes.

The PDF417 barcode decoding chip of the present invention adopts a hardware pipeline structure to realize recognition and decoding of barcode images through hardware logic. Since the hardware pipeline structure is suitable for pipeline operations and parallel processing of barcode images, the processing speed is very fast. Due to the use of a full hardware structure, no processor is required to participate in decoding. Compared with the processor, the chip structure is simpler in structure, smaller in area, lower in power consumption, lower in cost, easy to integrate, and easy to implement portable applications. It can be easily combined with the Internet of Things technology, providing a broader development space for the application of barcode technology.

【Description of drawings】

FIG. 1 is a structural schematic diagram of a method and device for reading barcodes in the prior art.

Fig. 2 is a schematic diagram of the PDF417 barcode decoding chip of the present invention.

Fig. 3 is a structural schematic diagram of the scanning module in the PDF417 barcode decoding chip of the present invention.

Fig. 4 is a schematic diagram of the recognition principle of the barcode direction recognition method according to the present invention.

Fig. 5 is a structural schematic diagram of the bar-space boundary processing module in the PDF417 barcode decoding chip of the present invention.

Fig. 6 is a schematic diagram of the working principle of the barcode image processing by the bar-space boundary processing module of the present invention.

FIG. 7 is a partially enlarged view of processing the barcode image in FIG. 6 .

Fig. 8 is a schematic structural diagram of a symbol character extraction module in the PDF417 barcode decoding chip of the present invention.

Fig. 9 is a structural schematic diagram of the decoding module in the PDF417 barcode decoding chip of the present invention.

【Detailed ways】

Regarding the features and technical content of the present invention, please refer to the following detailed description and accompanying drawings, which are provided for reference and illustration only, and are not intended to limit the present invention.

First, the PDF417 barcode decoding chip of the present invention will be described in detail below, and FIG. 2 is a schematic diagram of the PDF417 barcode decoding chip of the present invention. The PDF417 barcode decoding chip 10 of the present invention is connected to the data memory 11 . The data memory 11 is used for storing barcode image information. Barcode image information includes image pixel coordinates and image pixel grayscale values. The barcode image information is stored in the data memory 11 in a certain order. Further, the data memory 11 also includes an address storage space (not shown), the address storage space is used to store image pixel coordinates, an image pixel coordinate corresponds to an address bit in the address storage space, and the image pixel coordinates in the address storage space The storage method is sequential storage.

The PDF417 barcode decoding chip 10 includes a state control module 100, a scanning module 110, a boundary recognition module 120, a direction calculation module 130, a bar boundary processing module 140, a symbol character extraction module 150, a symbol parameter recognition module 160 and a decoding module 170.

The state control module 100 is used to control the working state and processing flow of the scanning module 110, the boundary recognition module 120, the direction calculation module 130, the strip-space boundary processing module 140, the symbol character extraction module 150, the symbol parameter recognition module 160 and the decoding module 170 .

Each module of the PDF417 barcode decoding chip of the present invention will be described in detail one by one in conjunction with Fig. 2-10.

Fig. 3 is a structural schematic diagram of the scanning module in the PDF417 barcode decoding chip of the present invention.

The scanning module 110 is used to establish a scanning coordinate system and generate scanning coordinates corresponding to address bits in the address storage space of the data memory 11 for scanning the barcode image information corresponding to the address bits in the data memory 11 . The scan module 110 includes a scan coordinate generation unit 111 and a coordinate mapping transformation unit 112 . The scan coordinate generation unit 111 is used to generate initial scan coordinates. The coordinate mapping transformation unit 112 is configured to map the initial scan coordinates generated by the initial scan coordinate generation unit 111 to the address storage space of the data memory 11 after coordinate transformation. The coordinate transformation function of the coordinate mapping transformation unit 112 includes at least one of coordinate translation transformation, coordinate rotation transformation, or coordinate axis interchange transformation, or a combination thereof. The coordinate transformation of the coordinate mapping transformation unit 112 can realize scanning of the barcode image in different directions.

The boundary identification module 120 reads the barcode image information corresponding to the address bits in the data memory 11 according to the scanning coordinates generated by the scanning module 110, and performs virtual scanning on the barcode image. The barcode image information includes image pixel coordinates and image pixel grayscale values. The so-called virtual scanning refers to obtaining the selected pixel coordinates and gray value of the barcode image through the scanning circuit according to a certain logic. Sweep the 2nd row in the direction. The boundary identification module 120 obtains the boundary points of the bar and space intersecting the virtual scanning line by calculating the coordinate positions of the pixel points with gray level difference on the virtual scanning line. For barcode symbols, bars are generally expressed in black or dark colors, and spaces are generally expressed in white or light colors. Furthermore, the boundary identification module 120 can also identify the barcode type according to the obtained bar-space boundary points. In one embodiment of the present invention, the boundary identification module 120 matches the obtained bar-space boundary points with the bar-space ratios of the start symbols or terminators of determinant barcodes such as PDF417 and Micro PDF417 to identify whether There are determinant barcodes such as PDF417 and Micro PDF417.

The direction identification module 130 calculates and obtains the direction of the barcode according to the boundary points of the bar and space acquired by the boundary identification module 120 . The method for obtaining the barcode direction by the direction recognition module 130 of the present invention will be described in detail below. FIG. 4 is a schematic diagram of the recognition principle of the barcode direction recognition method according to the present invention. As shown in Figure 4, the barcode image is in an inclined state, and it is impossible to directly make a virtual scanning line along the horizontal direction for identification and decoding. It is necessary to adjust the virtual scanning direction after obtaining the direction of the barcode. The angle included in the direction of the barcode in the first scanning direction is θ2, and since θ2 and θ1 are complementary angles to the unified angle, θ1=θ2. So you only need to know the slope tgθ1 of θ1 to get the slope tgθ2 of the barcode direction.

As can be seen from Figure 4, $\mathrm{tg\θ}1=-\frac{x_2-x_1}{{\mathrm{the\; y}}_2-{\mathrm{the\; y}}_1}.$

In the above formula, the coordinates of (x2, y2) and (x1, y1) can be obtained from the boundary points where the virtual scan line intersects with the bar space, and according to the coordinate values of the boundary points where each virtual scan line intersects with the bar space, pass X Coordinate position comparison, y coordinate position comparison to judge the parallelogram feature of each point, can determine the coordinates of the pixel points (x2, y2) and (x1, y1) located in a parallelogram feature, and then calculate and obtain the value of tgθ1, That is, the direction of the barcode is obtained. The above-mentioned parallelogram feature may also be replaced by a parallel line feature, and the above-mentioned parallelogram feature or parallel line feature is not limited to a space.

After the direction identification module 130 calculates the barcode direction, the bar-space boundary processing module 140 processes the barcode image according to the barcode direction, so as to obtain the accurate bar-space boundary in the barcode image.

Fig. 5 is a structural schematic diagram of a bar-space boundary processing module in the PDF417 barcode decoding chip of the present invention. As shown in FIG. 5 , the strip boundary processing module 140 further includes a scan boundary acquisition unit 141 , a line scan unit 142 , a sub-pixel boundary calculation unit 143 , a line calculation unit 144 and a scan coordinate calculation unit 145 . FIG. 6 is a schematic diagram of the working principle of the barcode image processing by the bar-space boundary processing module of the present invention, and FIG. 7 is a partial enlarged view of the barcode image processing in FIG. 6 . The structure, function and processing flow of each unit in the strip boundary processing module 140 will be described below with reference to FIG. 5 , FIG. 6 and FIG. 7 .

As shown in FIG. 5 , the scan boundary acquisition unit 141 is connected to the boundary identification module 120 and the direction calculation module 130 . The scan boundary acquisition unit 141 acquires the barcode boundary points from the boundary recognition module 120 , and acquires the barcode direction from the direction calculation module 130 .

As shown in FIG. 6 and FIG. 7 , the scan boundary acquisition unit 141 takes the barcode boundary points on both sides as the center, expands outward according to the barcode direction and the direction perpendicular to the barcode direction, and acquires boundary areas 821 and 826 respectively. Boundary areas 821 and 826 include a collection of barcode boundary points and nearby pixel points. The scan boundary acquisition unit 141 inputs the set of pixel points in the boundary areas 821 and 826 into the line calculation unit 144 , and the line calculation unit 144 performs Hough (Hough) operation on the set of pixel points in the boundary areas 821 and 826 . The basic principle of the Hough operation is as follows: Assuming that there is a straight line with a distance from the origin of ρ and an azimuth angle of θ in the Cartesian coordinate system, each point on the line satisfies the formula ρ=xcosθ+ysinθ. In the process of barcode boundary search, for the image space coordinates x and y of each pixel point, use different θ discrete values to calculate the corresponding ρ value through the above calculation formula, and obtain the straight line by statistics of θ discrete value and ρ value The corresponding pixel coordinates. In an embodiment of the present invention, the straight line calculation unit 144 may, for example, use a plurality of serially connected cordic iterative calculation units to implement Hough calculation on a set of pixel points to obtain the straight line coordinates.

The straight line calculation unit 144 obtains the pixel point coordinates of the boundary line 822 corresponding to the barcode boundary in the boundary area 821 and the pixel point coordinates of the boundary line 827 corresponding to the barcode boundary in the boundary area 826 through the Hough operation, and returns the calculation result to the scanning boundary Acquisition unit 141. The boundary straight lines 822 and 827 reflect the straight line characteristics of the empty boundaries in the boundary areas 821 and 826 .

The scanning boundary acquisition unit 141 shifts the pixel coordinates of the boundary line 822 and the boundary line 827 to the outside of the barcode area by a predetermined distance to obtain the scanning boundaries 823 and 828 according to the direction of the barcode. The predetermined distance is, for example, 5-10 pixel points. The boundary lines 822 and 827 reflect the straight line characteristics of the bar-space boundary, but due to the influence of barcode printing or barcode imaging, the actual bar-space boundary in the barcode image is not a strict straight line, but a slight fluctuation based on the line feature. A collection of curves or multiple straight line segments. In order to obtain a more accurate strip boundary, the scan boundary acquisition unit 141 translates the pixel point coordinates of the boundary straight line 822 and the boundary straight line 827 outward, so that the curve with slight fluctuations based on the straight line feature or the set of multiple straight line segments Included within scan boundaries 823 and 828 . Afterwards, the scanning boundary acquisition unit 141 inputs the scanning boundaries 823 and 828 into the linear scanning unit 142 for the next step of processing.

The linear scanning unit 142 selects a point A on one side of the scanning boundary 823 , and obtains a point A′ corresponding to the point A on the other side of the scanning boundary 828 . Point A' includes a variety of acquisition methods. In one embodiment of the present invention, the method for obtaining point A' is to use point A as the starting point, and search for point A' on the same straight line as point A on the scanning boundary 828 according to the direction of the barcode (ie, the value of tgθ1), That is, according to the known straight line, the coordinates of the coordinate point A outside the straight line, and the slope value of another straight line passing through point A, the coordinates of the intersection point A' of the known straight line and another straight line are obtained. In another embodiment of the present invention, the method for obtaining point A' is to calculate the coordinate point with the shortest distance from point A on the scanning boundary 828, and the coordinate point is point A'.

The linear scanning unit 142 takes A as the scanning starting point and A' as the scanning end point, and calculates the coordinates of the pixels on the straight line 824 between A-A'. The line scanning unit 142 inputs the coordinate values of point A and point A' into the scanning coordinate calculation unit 145, and the scanning coordinate calculation unit 145 calculates the coordinates of the pixel point 825 on the line 824 between A-A'.

The method for calculating the coordinates of the pixel point 825 by the scan coordinate calculation unit 145 includes various methods. In one embodiment of the present invention, the scan coordinate calculation unit 145 includes a Breshem calculation unit, and the Breshem calculation unit calculates the coordinates of each pixel point on the straight line 824 between two points A-A′. The principle of the Breshem algorithm is as follows: the barcode image is composed of pixels, and a group of virtual grid lines are constructed through the pixel centers of each row and column in the barcode image. Computes the intersection point of the line with each vertical grid line in order from the start point to the end point of the line, and then determines the pixel in the column of pixels closest to the intersection point. The ingenuity of the Breshem algorithm lies in the use of incremental calculations, so that for each column, only by checking the sign of an error term, the coordinates of the requested pixel point of the column can be determined. Breshem makes all calculations with integers in the process of finding the coordinates of each point on the straight line between two points, thus greatly improving the calculation speed.

The scanning coordinate calculation unit 145 returns the calculated coordinates of the pixel point 825 on the straight line 824 between the two points A-A′ to the straight line scanning unit 142, and the straight line scanning unit 142 returns the pixel point on the straight line 824 between the two points A-A′ The coordinates of 825 are input into the sub-pixel boundary calculation unit 143.

The sub-pixel boundary calculation unit 143 performs sub-pixel boundary calculation according to the coordinates and gray value of the pixel point 825 between A-A', and divides the corresponding pixel point 825 into smaller units to obtain the precise coordinates of the strip-space boundary and calculate Get the gray level drop value corresponding to the precise coordinate.

Thus, the bar-space boundary processing module 140 has obtained the precise bar-space boundary coordinates in the barcode image and the grayscale drop value corresponding to the precise coordinates, and input the bar-space boundary data into the symbol character acquisition module 150 and the symbol parameter identification module 160 in.

Fig. 8 is a schematic structural diagram of a symbol character extraction module in the PDF417 barcode decoding chip of the present invention. As shown in FIG. 8 , the symbol character extraction module 150 of the present invention includes a bar-space determination unit 151 and a bar-space value calculation unit 152 .

Wherein, one end of the bar-space judging unit 151 is connected to the symbol parameter recognition module 160 and the bar-space boundary processing module 140, and the other end is connected to the bar-space value calculation unit 152, which stores the bar-space boundary data provided by the bar-space boundary processing module 140 and compares the bar-space boundary data therein The interference boundary is judged and eliminated to obtain an effective combination of strip and space boundaries.

Symbol parameter recognition module 160 is provided according to the bar space boundary data of bar boundary processing module 140, and the symbol parameter of barcode is identified, and symbol parameter comprises the row number of barcode, column number, line number, column number, the bar space boundary of symbol character number, bar space width of symbol characters, checksum information, etc. The method for the symbol parameter identification module 160 to identify symbol parameters includes multiple methods such as cluster number calculation and code system judgment.

The stripe-space determination unit 151 processes the stripe-space boundary data provided by the stripe-space boundary processing module 140 according to the symbol parameters provided by the symbol parameter identification module 160 , and excludes the interference boundaries therein. The specific work process of the bar space judging unit 151 is as follows: when the bar space boundary quantity stored in the bar space judging unit 151 does not reach the bar space boundary number in the symbol parameter, the bar space judging unit 151 continues to obtain the bar space boundary processing module 140 to provide. Empty boundary data. When the number of bar space boundaries stored by the bar space judging unit 151 reaches the bar space boundary number in the symbol parameter, the bar space judging unit 151 calculates the bar space width value of the bar space boundary combination stored, and stores the bar space boundary The combined bar space width value is compared with the bar space width in the symbol parameter, and when the bar space width value of the bar space boundary combination stored is less than the bar space width in the symbol parameter, the bar space determination unit 151 excludes the stored gray The strip-space boundary with the smallest degree drop width, and continue to obtain the strip-space boundary provided by the strip-space boundary processing module 140. When the bar space width value of the bar space boundary combination stored reaches the bar space width in the symbol parameter, the bar space determination unit 151 outputs the stored bar space boundary combination to the bar space value calculation unit 152 .

The bar-space value calculation unit 152 obtains the coordinates and the grayscale drop value of each bar-space boundary in the combination of bar-space boundaries, and calculates the bar-space width value formed by each bar-space boundary by comparison, and then obtains the symbol character, and calculates The symbol characters are input into the decoding module 170 .

Fig. 9 is a structural schematic diagram of the decoding module in the PDF417 barcode decoding chip of the present invention. As shown in FIG. 9 , the decoding module 170 of the present invention includes a codeword acquisition unit 171 , a codeword error correction unit 172 , a decoding unit 173 and a code table storage unit 174 . The decoding module 170 converts the symbol characters provided by the symbol character extraction module 150 into code words and performs error correction decoding to obtain barcode information, and then inputs the barcode information into the decoding information storage area of the data memory 11 .

Wherein, the code table storage unit 174 stores a code table representing the corresponding relationship between symbol characters and code words. The codeword acquiring unit 171 acquires an initial codeword by using the received symbol characters according to the code table. The codeword error correction unit 172 performs RS error correction processing on the initial codeword to obtain a correct codeword. The decoding unit 173 obtains the correct symbol character by using the correct code word according to the code table, and decodes according to the character set corresponding to the correct symbol character to obtain barcode information.

The code table storage unit 174 stores a code table of the corresponding relationship between symbol characters and code words. Wherein, the symbol characters correspond to different bar-null value combinations of the barcode. The code table storage unit 174 stores the code table in ROM (Read-Only Memory, read-only memory).

The PDF417 barcode decoding chip of the present invention can automatically identify the direction of the barcode, realize the identification and decoding of the barcode image without the user adjusting the scanning direction of the scanning unit, and has high identification accuracy of the barcode boundary and a high decoding success rate.

The PDF417 barcode decoding chip of the present invention can adjust the decoding direction according to the direction of the barcode, obtain the precise coordinate value of the barcode boundary, greatly improve the decoding success rate, and is especially suitable for the identification and decoding of high-density barcodes or distorted barcodes.

The PDF417 barcode decoding chip of the present invention adopts a hardware pipeline structure to realize recognition and decoding of barcode images through hardware logic. Since the hardware pipeline structure is suitable for pipeline operations and parallel processing of barcode images, the processing speed is very fast. Due to the use of a full hardware structure, no processor is required to participate in decoding. Compared with the processor, the chip structure is simpler in structure, smaller in area, lower in power consumption, lower in cost, easy to integrate, and easy to implement portable applications. It can be easily combined with the Internet of Things technology, providing a broader development space for the application of barcode technology.

Various preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but as long as they do not depart from the essence and scope of the present invention, those skilled in the art can carry out various modifications and changes to it, all of which belong to the protection of the present invention scope.

Claims (16)

1. A PDF417 bar code decoding chip is characterized in that, comprising: The scanning module generates scanning coordinates, the scanning coordinates correspond to the address bits in the address storage space of the data memory, and are used to scan the barcode image in the data memory; The boundary identification module reads the barcode image according to the scanning coordinates, and calculates the read image pixel points to obtain the bar-space boundary points of the barcode image; a direction recognition module, calculating and obtaining the direction of the barcode according to the boundary points of the barcode acquired by the boundary recognition module; The bar-space boundary processing module processes the barcode image according to the barcode direction, so as to obtain the bar-space boundary in the barcode image; The symbol parameter identification module identifies the symbol parameters of the barcode according to the empty boundary of the bar, so as to obtain the symbol parameters; A symbol character acquisition module, calculating and obtaining a symbol character according to the empty boundary and the symbol parameter; and The decoding module converts the symbolic characters into barcode information. 2. PDF417 bar code decoding chip according to claim 1, is characterized in that, described scanning module comprises scanning coordinate generation unit and coordinate mapping transformation unit, and described scanning coordinate generation unit produces initial scanning coordinate, and described coordinate mapping transformation unit and mapping the initial scan coordinates to the address storage space after coordinate transformation. 3. The PDF417 barcode decoding chip according to claim 1, wherein the boundary identification module obtains the bar-space boundary points of the barcode image by calculating the gray level difference of the image pixels. 4. The PDF417 barcode decoding chip according to claim 1, wherein the boundary identification module identifies the barcode type according to the bar-space boundary points of the barcode image. 5. PDF417 bar code decoding chip according to claim 4, is characterized in that, described boundary identification module matches the bar space ratio of described bar empty boundary point and the start character of certain bar code or terminator, to identify Whether this kind of barcode exists in the barcode image. 6. PDF417 barcode decoding chip according to claim 1, is characterized in that, described direction identification module judges the feature relation of described bar empty boundary point by the coordinate position comparison of described bar empty boundary point, by being located in the same feature The coordinate values of the bar empty boundary points within the relationship are used to calculate the barcode direction. 7. The PDF417 barcode decoding chip according to claim 6, wherein the feature relationship comprises a parallelogram feature or a parallel line feature. 8. PDF417 barcode decoding chip according to claim 1, is characterized in that, described bar empty boundary processing module comprises: A scan boundary acquisition unit, which acquires the bar space boundary point and the barcode direction, and calculates the scan boundary; a linear scanning unit, selecting a scanning starting point and a scanning end point corresponding to the scanning starting point according to the scanning boundary, and calculating coordinates of pixels on a straight line between the scanning starting point and the scanning end point; and The sub-pixel boundary calculation unit calculates the coordinates of the strip boundary according to the coordinates of the pixel points and the gray value of the pixel points. 9. PDF417 barcode decoding chip according to claim 8, is characterized in that, described scanning boundary acquisition unit is centered on described bar empty boundary point, according to described barcode direction outward expansion, obtains boundary area, and described boundary The area includes the barcode boundary point and a set of pixel points near the barcode boundary point. 10. The PDF417 barcode decoding chip according to claim 9, wherein the empty boundary processing module of the bar also includes a straight line calculation unit, and the straight line calculation unit obtains the corresponding boundary straight line of the boundary area by Hough operation . 11 . The PDF417 barcode decoding chip according to claim 10 , wherein the scan boundary acquisition unit shifts the boundary line a predetermined distance outside the barcode area according to the barcode direction to obtain the scan boundary. 12. The PDF417 barcode decoding chip according to claim 8, wherein the bar-space boundary processing module also includes a scanning coordinate calculation unit, and the scanning coordinate calculation unit calculates the scanning starting point and the scanning coordinates by the Breshem algorithm. The coordinates of the pixel points on the line between the endpoints. 13. PDF417 barcode decoding chip according to claim 1, is characterized in that, described symbol parameter comprises the line number of barcode, column number, row number, column number, bar space boundary number of symbol character, bar space of symbol character One of width, checksum, or a combination thereof. 14. PDF417 bar code decoding chip according to claim 1, is characterized in that, described symbol character extracting module comprises bar empty judging unit, and described bar empty judging unit processes described bar empty boundary according to described sign parameter, Exclude the interfering boundaries in the strip-space boundaries to obtain an effective combination of strip-space boundaries. 15. PDF417 bar code decoding chip according to claim 14, it is characterized in that, described sign character extracting module also comprises bar empty value calculation unit, described bar empty value calculation unit is combined by comparing described effective bar empty boundary Composition of the bar space width value, get the symbol character. 16. PDF417 barcode decoding chip according to claim 1, is characterized in that, described decoding module comprises: A code table storage unit stores a code table representing the corresponding relationship between the symbol character and the code word; a codeword acquiring unit, which acquires an initial codeword by using the received symbol characters according to the code table; A codeword error correction unit, which performs RS error correction processing on the initial codeword to obtain a correct codeword; and The decoding unit obtains the correct symbol character by using the correct code word according to the code table, and performs decoding according to the character set corresponding to the correct symbol character to obtain the barcode information.

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