in the FlexiLayout tree.
Character String elements are used to look for unspecified text. The program considers as candidates the Recognized Words objects detected during pre-recognition in the element’s search area.
Usually, character strings are located next to static text. When looking for the Ref. No. of a document, for example, the program must first find the static text “Ref. No.” and then look for digits next to it.
Describe the search text
Click the Character String tab in the Properties dialog box to describe the corresponding object. To open the Properties dialog box, right-click the element in the FlexiLayout tree and select Properties… on the shortcut menu.
Describe search text with a regular expression
A regular expression defines possible combinations of characters. If you use a regular expression, the hypothesis must meet its conditions. This method is usually used on good-quality documents that are recognized without errors. To enter a regular expression, select the Regular expression option and enter the expression in the field next to it. You can also click the
button, which opens a drop-down list of options (Any Letter, Character From Set, and so on). Select the option to enter the corresponding regular expression into the field.
Regular expression syntax
| Name in the list | Symbol in the field | Example |
|---|---|---|
| Any character | * | “k”*“t” – allows ‘kit’, ‘kat’, and so on. |
| Letter | C | C”at” – allows cat, bat, Rat, mat, and so on. |
| Upper case letter | A | A”at” – allows Cat, Bat, Rat, Mat, and so on. |
| Lower case letter | a | a”at” – allows cat, bat, rat, mat, and so on. |
| Letter or digit | Х | X – allows any single letter or digit. |
| Digit | N | N”th” allows 5th, 4th, 6th, and so on. |
| String | "" | "cat” |
| Or | | | “dr”(“i”|“u”)“nk” – allows “drink” or “drunk”. |
| Character from the set | [] | [hm]“at” – allows ‘hat’ or ‘mat’. |
| Character not from the set | [^] | [^b]“at” – allows ‘cat’, ‘mat’, ‘rat’, but does not allow bat. |
| Any number of repeats (applies to the expression or sub-expression to the left) | {-} | [AB74]{-} – allows any combination of A, B, 7, 4 of any length. |
| Number of repeats is n | {n} | N{2}“th” allows 25th, 84th, 11th, and so on. |
| n to m repeats | {n-m} | N{1-3}“th” allows 5th, 84th, 111th, and so on. |
| 0 to n repeats | {-n} | N{-2}“th” allows th, 84th, 4th, and so on. |
| n or more repeats | {n-} | N{2-}“th” allows 25th, 834th, 311th, 34576th, and so on. |
| Subexpression | () |
Describe search text with an alphabet
An alphabet lists characters that can occur in the search text. This method is used whenever the character string cannot be described with a regular expression or there are too many errors in the recognized text as a result of poor image quality. You can specify several alphabets for a Character String element. If the format of the text is unknown, no alphabets are specified. In this case, the program considers all possible characters when looking for the object corresponding to the element. To describe search text with an alphabet:- Select a hypothesis generation mode. To use the characters in the search area to generate all the possible hypotheses, including intersecting and embedded hypotheses, select Allow embedded hypotheses. To generate hypotheses of maximum length, clear Allow embedded hypotheses.
- Create one or more alphabets.
- Click Add….
- In the Add New Alphabet dialog box, select the required code page from the Code page list.
- In the Character map, select the characters that occur in the search text. The selected characters and their number are displayed in the Selected on screen/selected in all field.
- In the Percentage of alphabet characters field, specify the required percentage of alphabet characters in the search text.
You can specify several alphabets, but they must not overlap, that is, include the same characters.
- Select Whole words only to find whole words only.
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Use the Detect words by interword space option to specify how lines are divided into words. Disable this option to detect words automatically. Enabling this option divides a line into words whenever the space between neighboring characters is greater than or equal to the value entered in Min interword space.
In the case of automatic word detection, word ends are detected based on spaces or other symbols that separate words (for example,
,,;,/,?- the exact set of symbols depends on the selected pre-recognition language), or based on other attributes. To make sure that the program correctly divides lines into words, review the text objects on the test images (View → Images → Objects → Recognized Words). - In the Word count fields, specify the number of words in the character string. The number of words is specified using a fuzzy interval. The default interval is {-1,-1,INF,INF} (that is, the program looks for hypotheses containing any number of words).
- In the Max space length field, specify the maximum length of the space inside the object. It is measured in the user-defined units of measurement. You can estimate the length of the space by looking at the coordinates of the neighboring objects. Rest the mouse cursor on a neighboring object to display its coordinates in the status bar. When looking for text, characters are added to the character string until the distance between neighboring elements exceeds Max space length.
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In the Character count field, specify the length of the character string (that is, the number of characters in the string). The number of characters is specified using a fuzzy interval and assesses the quality of the hypothesis based on its length.
Use the
button to specify fuzzy intervals in a separate window that visualizes them.