JP3571781B2 - Mail processing apparatus and mail processing method - Google Patents

Description

【００４２】
すなわち、上述した座標変換回路４６の構成は上式をハード化したもので、ＲとＡを乗じたものとＳとＢを乗じたものを加えたものをＸとし、ＲとＣを乗じたものとＳとＤを乗じたものを加えたものをＹとしている。Ａ、Ｂ、Ｃ、Ｄは下式のように対応している。
【００４３】
【数２】

【００４４】
この式からわかるように、Ａ、Ｂ、Ｃ、Ｄは下地色Ｕｇ（Ｍｈｒ、Ｍｈｓ）により決定している。従って、郵便書状Ｐの下地色は１通毎に異なるので、回転変換のパラメータＡ、Ｂ、Ｃ、Ｄは１通毎に異なる値となる。つまり、その郵便書状毎に適応する回転変換がなされるわけである。パラメータＡ、Ｂ、Ｃ、Ｄの計算はＣＰＵ３０でプログラムメモリ３１に記憶されているプログラムによって行われ、郵便書状１通毎にＣＰＵ３０より乗算器５３，５４，５５，５６に設定される（ステップＳＴ７）。
【００４５】
つぎに、本実施例の目的とする色の領域を切り出すために２値化を行う（ステップＳＴ１０）。
図１３において、座標変換された明るさの２次元分布図ではヒストグラムの頻度の高い下地色周辺の色はＸ軸上Ｆ１周辺に分布する。また、文字などの明るさの低い色（黒色）もＸ軸上のＦ２周辺に分布する。このことから、下地色周辺の色と黒画像を他色と分離するために第１の閾値（ＴＨＲＡ）を設ける。ＴＨＲＡは次式で設定される。
ＴＨＲＡ＝Ｃｓ_１ ×Ｃｖ×（Ｍｈｓ＋（Ｍｈｒ−Ｍｈｓ）×Ｃｃ_１ ／Ｍｈｒ
ここで、Ｃｓ_１ は定数、Ｃｖは原点から下地色までの距離によって決まる値、Ｃｃ_１ は原点から下地色までの直線の傾きによって決まる値である。
【００４６】
そして、つぎに色の濃度値の違いによって色を分離する。そのための第２、第３の閾値がＴＨＲＢ、ＴＨＲＣである。このふたつの値は原点から下地色Ｕｇ（Ｍｈｒ、Ｍｈｓ）までの距離の定数倍である。
【００４７】
ＴＨＲＡ、ＴＨＲＢ、ＴＨＲＣの計算式は、ＣＰＵ３０のプログラムメモリ３１内にプログラムされている。ＴＨＲＡ、ＴＨＲＢ、ＴＨＲＣの値は、郵便書状１通毎にＣＰＵ３０からコンパレータ６０，６１，６２に設定される（ステップＳＴ８）。
【００４８】
ＣＰＵ３０から送られたＴＨＲＡ、ＴＨＲＢ、ＴＨＲＣの値は、それぞれコンパレータ６０，６１，６２で画像データと比較される。そしてコンパレータ６０，６１，６２の出力であるＡＧＢ、ＡＬＢをＣＰＵ３０から選択し、３つのコンパレータ６０，６１，６２の出力の和を加算器６６で取り２値化データとする（ステップＳＴ１０）。これによって２次元分布図のさまざまなエリアを切り出すことが可能となる。
【００４９】
例えば、図１３の斜線部を切り出したい場合、ＣＰＵ３０からコンパレータ６０ではスイッチ６３を介してＡＬＢを選択し、コンパレータ６１ではスイッチ６４を介してＡＧＢを選択し、コンパレータ６２ではスイッチ６５を介してＡＬＢを選択するようにしてやればよい。図１３の斜線部は図７のＮで示す料金計器（赤画像）に対応しているので、料金計器の印影だけが取出せるわけである。
【００５０】
なお、閾値を変化させたり、コンパレータ６０，６１，６２の出力の選択を変えることによって赤画像だけでなく他の色を抽出することが可能である。例えば、図１３でＸ＜ＴＨＲＢかつＹ＜｜ＴＨＲＡ｜とすれば黒文字が抽出できるし、Ｘ＞ＴＨＲＣかつＹ＜｜ＴＨＲＡ｜とすれば下地色が抽出できる。
【００５１】
こうして切り出された２値化データは画像処理部４８に送られる。
そして、画像処理部４８で処理されたデータは、バス３６を介してＣＰＵ３０に送られ料額印の判定がされる（ステップＳＴ１１）。
【００５２】
以上説明したように上記実施例によれば、１通毎に郵便書状の下地色を見つけだし、その書状に適した２値化のための座標変換、閾値の設定が行えるので下地の色がどんな色であろうと料額印とある程度の色の差があれば、料額印の検出が可能となる。また、色の明るさ２次元分布のエリア切出しによって料額印を抽出しているため、容易に検出が可能である。
【００５３】
【発明の効果】
以上詳述したようにこの発明によれば、蛍光が薄くても、あるいは蛍光を全く含んでいない料金計器でも容易に検出することのできる郵便物処理装置および郵便物処理方法を提供することができる。
【図面の簡単な説明】
【図１】この発明の一実施例における郵便物選別取揃え押印機の全体の構成を示すブロック図。
【図２】図１の郵便物選別取揃え押印機の外観図。
【図３】図１の郵便物選別取揃え押印機を上方から見た平面図。
【図４】ヒストグラム回路の構成例を示す図。
【図５】座標変換回路の構成例を示す図。
【図６】２値化回路の構成例を示す図。
【図７】郵便書状の例を示す図。
【図８】郵便書状の読取り動作について説明するためのフローチャート。
【図９】Ｒ画像とＳ画像の明るさの２次元分布を示す図。
【図１０】ＲとＳそれぞれの方向に明度のヒストグラムを示す図。
【図１１】アドレスとＷＲ信号とデータとの関係を示す図。
【図１２】新しい座標をＸ軸、Ｙ軸としたときの２次元分布を示す図。
【図１３】座標変換された明るさの２次元分布における閾値を説明するための図。
【符号の説明】
１…郵便物選別取揃え押印機
３０…ＣＰＵ
３２…カラーセンサ
４０…限定色検知回路
４１，４２…Ａ／Ｄ変換器
４３，４４…多値メモリ
４５…ヒストグラム回路
４６…座標変換回路
４７…２値化回路
４８…画像処理部[0001]
[Industrial applications]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mail processing apparatus and a mail processing method such as an automatic mail sorting and stamping machine for automatically sorting, sorting, stamping and sorting mail .
[0002]
[Prior art]
2. Description of the Related Art A mail processing apparatus has been put into practical use as an automatic mail sorting and stamping machine for automatically sorting, sorting, stamping and sorting mail. This mail processing apparatus has an automatic sorting unit, an automatic reading unit, and a sheet stacking unit. The automatic sorting section automatically sorts and arranges mail items, the automatic reading section reads and stamps the information of the mail items, and then sorts them. The paper sheet stacking section stacks the sorted mail items.
[0003]
Conventionally, the detection of the postage mark of a postal letter in such a mail processing apparatus is performed by a stamp of a fixed position, a color and a size, a color detection circuit for detecting a fee, and the light emission of a phosphor applied to the stamp. There is a fluorescent phosphorescence detection circuit for detecting.
[0004]
However, toll meters stamped on postal letters contain fluorescent paint in most cases, but there are also toll meters that have little or no fluorescent light. Such a charge meter could not be detected.
[0005]
[Problems to be solved by the invention]
As mentioned above, toll meters stamped on postal letters almost always contain fluorescent paint, but there are toll meters with little or no fluorescence at all, such as fluorescent phosphorescence. The detection circuit has a problem that such a meter cannot be detected.
[0006]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a mail processing apparatus and a mail processing method that can easily detect even a fee meter that has little or no fluorescence.
[0007]
[Means for Solving the Problems]
A mail processing apparatus according to the present invention includes a color sensor for reading an image of a surface of a mail to be conveyed, and a first analog-to-digital converter for converting an analog red image of the image read by the color sensor into a digital image. And a second analog-to-digital converter for converting an image other than an analog red image into a digital image from among the images read by the color sensor; the first analog-to-digital converter and the second analog-to-digital converter A histogram circuit for taking histograms in the red and non-red directions from the red image and the non-red image digitally converted in the above, and obtaining the most frequent value from the histogram in each direction taken by this histogram circuit Means for detecting the background color of the postal matter, and rotationally converting the coordinates of the image based on the background color detected by the detection means. A coordinate conversion circuit, a binarization circuit for binarizing a red area from the image rotationally converted by the coordinate conversion circuit, and an image processing for performing image processing on the image binarized by the binarization circuit And a judging means for judging the toll meter on the surface of the mail from the image processed by the image processing unit.
[0012]
[Action]
The present invention reads an image of the surface of a postal matter to be conveyed by a color sensor, converts an analog red image into a digital image among the images read by the color sensor, and converts an analog red image into an image read by the color sensor. The analog non-red image is converted to digital, and from the digitally converted red image and the non-red image, histograms in the respective red and non-red directions are taken. Calculate the value, detect the background color of the postal matter, rotate and convert the coordinates of the image based on the detected background color, and binarize the red area from the rotated image of the coordinates. The binarized image is subjected to image processing, and the toll meter on the mail surface is determined from the image processed image.
[0016]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIGS. 2 and 3 schematically show a mail sorting and stamping machine 1 as a mail processing apparatus of the present invention.
[0017]
That is, the mail sorting and stamping machine 1 includes a supply unit 2 for supplying a postal letter P, and a postal letter P supplied to the supply unit 2 is combined with a postal letter P having a fixed thickness and a postal letter having a non-standard thickness. A first sorting unit 3 for sorting the postal letters P, a conveyor (not shown) for conveying the postal letters P having a fixed thickness selected by the first sorting unit 3, and standing the postal letters P from the conveyor. The postal letter P is sorted into a postal letter P of a fixed size and a postal letter P of a non-standard size, and the vertical and horizontal directions of the postal letter P are aligned (the physical directions are aligned). The second sorting unit 5 conveys the fixed letter P from the second sorting unit 5 one by one, reads the sorting destination, determines the direction of the letter P by stamp detection, and makes this determination. Arrangement stamping unit 6 that aligns the upper and lower parts of postal letter P according to the contents, and stamps the postmark. The postal letter P from the call seal portion 6 is constituted by segment stacking section 7 for sorting and stacking on the basis of the read contents of the sorting destination.
[0018]
An operation panel 8 for instructing various operations and displaying an operation mode, an abnormal display, and the like is provided in a central portion of the mail sorting and stamping machine 1, that is, in the vicinity of the stamping section 6.
[0019]
The supply unit 2 includes a receiving unit 11 that collectively receives a plurality of postal letters P,..., And a transporting unit 12 that leveles the postal letters P from the receiving unit 11 by transporting the postal letters P obliquely upward.
[0020]
The supply unit 2 is installed at a position parallel to the second sorting unit 5, but is not limited to this, and is moved together with the first sorting unit 3 so that the second sorting unit 5 and the second sorting unit 5 are moved together. It can be installed at any position at a position rotated by approximately 360 degrees, such as a direction orthogonal to the second sorting unit 5 and a direction in which the second sorting unit 5 is connected in series (a direction in which the sorting unit 5 is aligned).
[0021]
For this reason, the degree of freedom of the layout for installing the apparatus is high.
The mail letter P having a fixed thickness selected by the first sorting unit 3 is dropped onto a conveyor (not shown) via a runway (not shown), and the mail letter P having a thickness other than the fixed thickness is rejected. (Not shown).
[0022]
The second sorting unit 5 includes a standing conversion unit 13 that sets the postal letter P from the conveyor to an upright state, a transport path 14 that conveys the postal letter P that has been set up by the standing conversion unit 13, One of the sorting units 15a, 15b, 15c that sorts out the non-standard-sized postal letters P with respect to the postal letters P conveyed by the conveying path 14, and one that supplies the postal letters P to the take-out buffer unit 17 one by one. It is composed of a take-out unit 15d.
[0023]
The non-standard-sized mail letter P selected by the selection units 15a, 15b, and 15c is repelled to a reject unit via a not-shown elimination conveyance path and a shooter.
[0024]
The alignment stamping section 6 includes a transport path 16 for transporting the standard postal letter P from the second sorting section 5, a buffer section 17 for accumulating the postal letter P transported by the transport path 16, and a buffer section 17. A buffer take-out section 18 for taking out the postal letters P collected one by one, an auxiliary supply section 19 to which a standard postal letter P is supplied when the alignment and stamping section 6 is used alone, and a mail supplied to the auxiliary supply section 19 A take-out section 20 for taking out the letters P one by one, a postal letter P taken out of the buffer section 17 by the buffer take-out section 18 or a transport path 21 for carrying a postal letter P taken out of the auxiliary supply section 19 by the take-out section 20. The first and second detectors 22 and 23, which detect stamps of postal letters P conveyed along the conveyance path 21 and read the sorting information, are conveyed by the conveyance path 21. That reversing unit 24 that reverses to align the top and bottom or the like of the postal letter P, is constituted by a stamped portion 25 to seal the postmark against postal letter P which has passed through the second detector 23.
[0025]
The first and second detectors 22 and 23 each include a not-shown stamp detector, a charge meter, and a receiver-paid detector.
The sorting / accumulating unit 7 includes gates 26,... Driven in accordance with the sorting information read by the first and second detecting units 22, 23, and a postal letter P sorted by these gates 26,. .., 27f to be integrated. The stackers 27a,..., 27f are assigned stacker numbers 1,.
[0026]
The operation panel 8 includes a display section 8a for displaying a jam position, operation guidance, and the like, an interlock switch 8b for instructing that the apparatus and a sorting machine connected to the apparatus move in conjunction with each other, and only this apparatus is used. It is constituted by a single-acting switch 8c for instructing to move by movement.
[0027]
FIG. 1 shows a control system of the mail sorting / arranging and stamping machine 1, a CPU 30 for controlling the entire system, a program memory 31 for storing a program for calculating parameters, etc., and a color sensor 32 for reading an image of a mail letter P. A limited color detection circuit (detection means) 40 for extracting only a specific color based on an image from the color sensor 32 and detecting a charge mark of a charge meter or the like, a postal letter provided immediately before the color sensor 32 and conveyed. It comprises a photocell sensor 34 for detecting the transport of P, a control circuit 35 for controlling various operations by signals from various sensors including the photocell sensor 34, and a bus 36.
[0028]
The limited color detection circuit 40 includes an A / D converter 41 that performs analog / digital (A / D) conversion of a red image (R image) from the color sensor (reading unit) 32, and a non-red image ( A / D converter 42 for analog / digital (A / D) conversion of S image), multivalued memory 43 for storing digital image (R image) from A / D converter 41, and A / D converter 42 , A digital image (R image) from the A / D converter 41 and a digital image (S image) from the A / D converter 42 are input and a histogram is stored. Circuit (histogram means) 45 for creating a coordinate conversion circuit (coordinates) for converting the coordinates of the image (R image) stored in the multi-valued memory 43 and the image (S image) stored in the multi-valued memory 44 conversion Stage) 46, a binarizing circuit (binarizing means) 47 for performing binarization in the X direction and the Y direction subjected to coordinate conversion by the coordinate converting circuit 46, and image processing using binary data from the binarizing circuit 47. And an image processing unit (image processing means) 48 for performing the following.
[0029]
FIG. 4 shows a configuration example of the histogram circuit 45, which is composed of a RAM 50 of 24 × 1024 bits and an adder 51.
FIG. 5 shows an example of the configuration of the coordinate conversion circuit 46, which includes multipliers 53, 54, 55, 56 and adders 57, 58.
[0030]
FIG. 6 shows a configuration example of the binarization circuit 47, which is composed of comparators 60, 61, 62, switches 63, 64, 65, and an adder 66.
FIG. 7 shows an example of a postal letter P. The background color is white L, several lines of addresses, the black portion M of the character portion on which the name is written, and the red portion N on which the stamp of the charge meter is stamped. It consists of each part.
[0031]
Next, the reading operation of the postal letter P in such a configuration will be described with reference to the flowchart of FIG.
First, when the postal letter P blocks the photocell sensor 34 installed in front of the image reading color sensor 32 (step ST1), the image of the postal letter P is transmitted from the color sensor 32 to a color other than a red image (R image) and red. (Step ST2).
[0032]
The captured image is subjected to analog-to-digital conversion by the A / D converters 41 and 42 for the R image and the S image (step ST3), and stored in the multi-value memories 43 and 44 (step ST4).
[0033]
FIG. 9 shows a two-dimensional distribution of the brightness of the R image and the S image at this time. The color L of the base color is distributed around F1, black M is distributed around F2, and red N is distributed around F3. are doing.
[0034]
At the same time as taking the images into the multi-value memories 43 and 44, brightness histograms are taken in the R and S directions (step ST5).
FIG. 10 shows brightness histograms in the R and S directions. In both the R direction and the S direction, the frequency of the histogram is high in the periphery (F1) where white as the base color is distributed.
[0035]
In the histogram circuit 45, the brightness of the image data is input to the address of the RAM 50. Then, in accordance with the WR signal, the data at the address is read from "OUT" of the RAM 50, "1" is incremented by the adder 51, and the data at the read address is written from "IN" of the RAM 50.
[0036]
FIG. 11 shows the relationship between the address, the WR signal, and the data. For example, when the address 17H (that is, the brightness 17H) at the time point a is input from the address line, the data value “0” of the address 17H is read from OUT of the RAM 50 when the WR signal is “1”. Then, "1" is added by the adder 51, and when the WR signal becomes "0", "0 + 1 = 1" is written from IN to the data value of the address 17H.
[0037]
Next, when the brightness 17H at the time point b is input to the address of the RAM 50, the data value "1" of the previous address 17H is read by the WR signal "1", "1" is added by the adder 51, and the WR signal is output. When it becomes "0", "1 + 1 = 2" is written in the data value of the address 17H. By repeating this process many times and repeating the process for the number of pixels of the captured image, a histogram of the brightness of the image can be obtained. On the basis of the obtained histogram, the most frequent value is obtained in each of the R direction and the S direction.
[0038]
The histogram result obtained by the histogram circuit 45 is sent to the CPU 30 via the bus 36, and the most frequent value is obtained in each of the R direction and the S direction. Then, this intersection is defined as Ug (Mhr, Mhs), and since this point has the largest number of pixels in the image, it is defined as the background color of the letter P (step ST6).
[0039]
Coordinate conversion is performed by the coordinate conversion circuit 46 as a preceding process for binarizing the image based on the base color (step ST9). By performing this coordinate conversion, binarization by the binarization circuit 47, which is the next process, can be easily performed. In the coordinate conversion, rotation conversion is performed such that a straight line connecting the base color Ug (Mhr, Mhs) and the origin overlaps the R axis.
[0040]
As shown in FIG. 12, when the new coordinates are the X-axis and the Y-axis, the conversion formula for rotating the angle θ around the origin by setting the angle formed by a straight line connecting the background color Ug (Mhr, Mhs) and the origin and the R-axis to θ is: It looks like this:
[0041]
(Equation 1)

[0042]
In other words, the configuration of the coordinate conversion circuit 46 described above is a hardened version of the above equation, in which a product obtained by multiplying R and A and a product obtained by multiplying S and B are added to X, and a product obtained by multiplying R and C is used. Y is the sum of S, D, and S. A, B, C, and D correspond to the following equations.
[0043]
(Equation 2)

[0044]
As can be seen from this equation, A, B, C, and D are determined by the base colors Ug (Mhr, Mhs). Accordingly, since the background color of the postal letter P differs for each copy, the parameters A, B, C, and D of the rotation conversion have different values for each copy. In other words, the rotation conversion adapted for each postal letter is performed. The calculation of the parameters A, B, C, and D is performed by the CPU 30 according to the program stored in the program memory 31, and is set in the multipliers 53, 54, 55, and 56 by the CPU 30 for each mail letter (step ST7). ).
[0045]
Next, binarization is performed in order to cut out a target color region of the present embodiment (step ST10).
In FIG. 13, in the two-dimensional distribution diagram of the coordinate-converted brightness, the colors around the background color having a high histogram frequency are distributed around F1 on the X-axis. Also, a low-brightness color (black) such as a character is distributed around F2 on the X-axis. For this reason, a first threshold (THRA) is provided in order to separate the color around the base color and the black image from other colors. THRA is set by the following equation.
THRA = Cs ₁ × Cv × (Mhs + (Mhr−Mhs) × Cc ₁ / Mhr
Here, Cs ₁ is a constant, Cv is a value determined by the distance from the origin to the background color, and Cc ₁ is a value determined by the slope of the straight line from the origin to the background color.
[0046]
Then, the colors are separated based on the difference in the density values of the colors. The second and third thresholds for this are THRB and THRC. These two values are constant multiples of the distance from the origin to the base color Ug (Mhr, Mhs).
[0047]
The calculation formulas of THRA, THRB, and THRC are programmed in the program memory 31 of the CPU 30. The values of THRA, THRB, and THRC are set in the comparators 60, 61, and 62 by the CPU 30 for each mail letter (step ST8).
[0048]
The values of THRA, THRB, and THRC sent from the CPU 30 are compared with image data by comparators 60, 61, and 62, respectively. Then, AGB and ALB which are the outputs of the comparators 60, 61 and 62 are selected from the CPU 30, and the sum of the outputs of the three comparators 60, 61 and 62 is taken by the adder 66 to be binary data (step ST10). This makes it possible to cut out various areas of the two-dimensional distribution map.
[0049]
For example, when it is desired to cut out the hatched portion in FIG. You only have to select it. Since the shaded portion in FIG. 13 corresponds to the charge meter (red image) indicated by N in FIG. 7, only the imprint of the charge meter can be taken out.
[0050]
It is possible to extract not only the red image but also other colors by changing the threshold or changing the selection of the outputs of the comparators 60, 61 and 62. For example, black characters can be extracted by setting X <THRB and Y <| THRA | in FIG. 13, and a base color can be extracted by setting X> THRC and Y <| THRA |.
[0051]
The binarized data thus cut out is sent to the image processing unit 48.
Then, the data processed by the image processing section 48 is sent to the CPU 30 via the bus 36, and the charge mark is determined (step ST11).
[0052]
As described above, according to the above-described embodiment, the base color of a postal letter is found for each letter, and coordinate conversion and threshold setting for binarization suitable for the letter can be performed. However, if there is a certain difference in color from the charge mark, the charge mark can be detected. Further, since the fee mark is extracted by extracting the area of the color brightness two-dimensional distribution, the detection can be easily performed.
[0053]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide a mail processing apparatus and a mail processing method that can easily detect even a fee meter that has little or no fluorescence. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing the entire configuration of a mail sorting / arranging and stamping machine according to an embodiment of the present invention.
FIG. 2 is an external view of the mail sorting and stamping machine of FIG.
FIG. 3 is a plan view of the mail sorting / sorting and stamping machine of FIG. 1 as viewed from above.
FIG. 4 is a diagram illustrating a configuration example of a histogram circuit.
FIG. 5 is a diagram illustrating a configuration example of a coordinate conversion circuit.
FIG. 6 is a diagram illustrating a configuration example of a binarization circuit.
FIG. 7 is a diagram showing an example of a postal letter.
FIG. 8 is a flowchart for explaining a postal letter reading operation.
FIG. 9 is a diagram showing a two-dimensional distribution of brightness of an R image and an S image.
FIG. 10 is a diagram showing lightness histograms in R and S directions;
FIG. 11 is a diagram showing a relationship among an address, a WR signal, and data.
FIG. 12 is a diagram showing a two-dimensional distribution when new coordinates are set to an X axis and a Y axis.
FIG. 13 is a diagram for explaining a threshold value in a two-dimensional distribution of coordinate-converted brightness.
[Explanation of symbols]
1. Mail sorting and stamping machine 30 CPU
32 color sensor 40 limited color detection circuits 41 and 42 A / D converters 43 and 44 multivalued memory 45 histogram circuit 46 coordinate conversion circuit 47 binarization circuit 48 image processing unit

Claims (2)

A color sensor that reads an image of the surface of the mail being conveyed,
A first analog-to-digital converter for converting an analog red image into a digital image among the images read by the color sensor;
A second analog-to-digital converter that converts an image other than an analog red image into a digital image among the images read by the color sensor;
A histogram circuit that takes a histogram in a red direction and a histogram in each direction other than red from a red image and a non-red image digitally converted by the first analog-digital converter and the second analog-digital converter,
Detecting means for obtaining the most frequent value from the histogram in each direction taken by the histogram circuit and detecting the background color of the postal matter;
A coordinate conversion circuit that rotationally converts the coordinates of the image based on the background color detected by the detection means;
A binarization circuit for binarizing a red area from the image rotationally transformed by the coordinate transformation circuit;
An image processing unit that performs image processing on the image binarized by the binarization circuit;
Determining means for determining a toll meter on the mail surface from the image processed by the image processing unit;
A mail processing apparatus comprising: A reading step of reading an image of the surface of the mail to be conveyed,
A first analog-to-digital conversion step of converting an analog red image of the images read in the reading step to digital;
A second analog-to-digital conversion step of converting an image other than analog red into a digital image among the images read in the reading step;
From the red image and the image other than red digitally converted in the first analog-to-digital conversion step and the second analog-to-digital conversion step, a histogram step of taking histograms in the red direction and the respective directions other than red,
A detection step of detecting a background color of the postal matter by obtaining a most frequent value from the histogram in each direction taken in the histogram step;
A coordinate conversion step of rotationally converting the coordinates of the image based on the background color detected in the detection step;
A binarization step of binarizing a red area from the image rotationally transformed in the coordinate transformation step;
An image processing step of performing image processing on the image binarized in the binarization step;
A judging step of judging a charge meter on the surface of the mail from the image processed in the image processing step;
A mail processing method, comprising:

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