Creating and testing a context using the MIL String Reader Interactive Utility

The MIL StringReader Interactive Utility allows you to create or edit an existing context to modify advanced settings and constraints. The utility provides a way to modify settings and preview your results in a streamlined process. Once you are satisfied with the results, you can import the context into Matrox Design Assistant.

The following procedure provides a basic methodology for creating and testing a context:

Create or open a new context.
Add a font to the context.
Add a string model to the context.
Optionally, define a search region.
Set the number of strings to read.
Preprocess and read.
View the results.
Optionally, use String Expert to diagnose results.

Create or open a new context

If you want to import an already existing context, click on the Import button.

If you are creating a new context, it is recommended that you use the .msr file suggested by Matrox Design Assistant. The context that is created is empty and you will need to add string model(s) and at least one font to it. To do so, perform the following:

Click on the Create button to start opening the MIL String Reader Interactive Utility. Matrox Design Assistant will create a blank context file and automatically import it the first time it is saved.
Click on Copy Path to Clipboard and then click on OK.
Once the MIL String Reader Interactive Utility is opened, import the blank context by opening the Open dialog and pasting the path you copied in step 2.

Once you are done modifying the context file, saving will automatically import it into Matrox Design Assistant.

Add a font

To add a font, click on Font Add from the Fonts tab. You can add a system font or a user-defined font from an image.

To define a font from an image, select UserDefined as the Mode and open an image which has the characters you are required to define. Draw a bounding box around the characters. In the Fonts tab, specify the characters which you are defining and click on Add.
To separate characters that are located on different lines, use a space.
The image you open must be 1-band, 8-bit unsigned.
To add a system font, select SystemFont as the Mode. To constrain the list of characters in the font, you can specify them or put a filter on the characters by choosing the appropriate one from the dropdown list.

Add a string model

To add a string model, click on String Add from the String Models tab to add a new string model to the context. You can specify properties such as the string and character score, minimum and maximum scale factor for the characters and put a constraint on the list of characters that can appear at each position.

The Score tab allows you to specify the acceptance and certainty score for a string or character. The higher the score, the better the candidate. If a string's score is higher than the specified acceptance threshold, then it is accepted by the read operation. If it is higher than the certainty score, then the read operation will stop searching for a better candidate. This will result in less image analysis and can speed up the read operation. For more information on scores, see the StringReader step scores section earlier in this chapter.
The String and Characters tab allow you to specify the minimum and maximum scale factor and aspect ratio.
The Constraints tab allows you to create rules to place constraints on the characters. To create a rule, set the type of character, the font and a list of valid characters that can appear for that position.

These settings can also be modified from Matrox Design Assistant.

Define a search region

You can optionally specify a search region to limit the area the utility will search for strings. To do so, perform the following:

Open your image by using the File Open menu item.
Define the region by using your mouse to enclose the area of interest.

The whole image will be used if you do not define a search region.

Set the number of strings to read

Set the total number of strings that can be read with the context by specifying the String Number property in the General tab. By default, one string will be read. If you set the property to All, all strings will be read. Note that this setting can increase the read time. It is recommended you set String Number to a specific number whenever possible.

Preprocess and read

Before you can read a string from the target image, you must preprocess it. Preprocessing essentially makes the context ready for the read operation. If you make any changes to the context, one of its fonts, or string models, you will need to preprocess the context again. To preprocess a context, click on the Preprocess button in the String Reader Context tab.

When you save the String Reader context, the preprocessing changes are not saved. Upon restoration, you must preprocess the context again.

Once the context has been preprocessed, the read operation can be performed by clicking on the Read button.

Viewing results

After a read operation has been performed, you can view the results from the Results pane. If any strings were found, the target image is overlayed with a bounding box around the string.

Once you are satisfied with the results, you can import the context into Matrox Design Assistant.

Using String Expert

String Expert allows you to diagnose your results and view a report on why a string was not read. The following shows the basic methodology of using String Expert.

Draw a bounding box around the string you want to read.
From the String Expert tab, specify the Target String you expect the StringReader step to read.
Enable Report Errors and Report Warnings.
Click on Start Expert to start the process.

For each string model you have defined, String Expert will give you a report on the settings that are preventing the StringReader step from reading the string.