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Optical Character Verification Vision 2007 4.10 User Manua l Rev 01 8 - 7 Train tab 1. Define the area ar ound the string to train (train only one line once a time). 2. Enter the characters of th e string that need s to …

Optical Character Verification

8 - 6 Vision 2007 4.10 User Manual Rev 01

The Median, Open and Close functions can also be used to clean the images.

Median analyses the image pixel by

pixel. Press Median button (B) to an-

alyze each pixel by looking at the val-

ues of the 8 pixels around the current

pixel. They are first sorted by gray

level. Whatever the value of the me-

dian pixel, the surrounding pixels

takes that level.

The Open function (C) enables

cleaning the image of its white noise (white pixels whose gray level is above the transition

average) and Close function (D) to clean the black noise (black pixels whose values are

lower than the average).

Seven values can be used for the Open and

Close functions. Each of the values masks,

cleans and restores the given number of pixels.

Save the new image if required. After saving, you can always modify the image. If you

are not satisfied with the image, you can return to the original image by clicking Restore

button (E).

Binarization uses the threshold value to

determine whether a pixel is black or white.

The threshold, in that case is set at 150.

Any pixel with a gray level lower than

150 will be black and any pixel with a

gray level above 150 will be white. Ad-

just the threshold so that the image is

containing relevant information.

Example: the goal is to eliminate noise to only get an L in the picture

Clean the black noise by setting the mask

dimension to 3 and selecting the Close

button.

All the objects within the image will be

trimmed by 1 pixel (CLEAR). The noise is

eliminated.

All that belongs to the image will be enlarged by 1 pixel at each edge. The only remain-

ing object is the L without any noise around.

If the image is useable for treatment, train the letters with the Train tab.

Image converted

into the binary

Original image

Before Median

After Median

Creation procedure

Mask dimensions

Value Cleaned and restored pixels

5 3

9 7

11 9

13 11

15 13

Optical Character Verification

Vision 2007 4.10 User Manual Rev 01 8 - 7

Train tab

1. Define the area around the string to train (train

only one line once a time).

2. Enter the characters of the

string that needs to be

trained (A) (without space

between two words).

3. Define if the characters are

Black on a White zone or

White on a Black zone

(B).

4. Use the Auto or Manual

segmentation (C) to adjust

the area around each

character of the string. The Auto will perform an automatic segmentation of the pic-

ture.

5. Modify the Coarse/Fine Grain Limit parameters (E) used to define the size of the vec-

tors used to detect transitions:

 Large transitions are detected with the Coarse grain limit.

 Small transitions are detected with the Fine grain limit.

6. When all characters are well surrounded, you can use the Train the

string button (F) to automatically train all the characters and add

them in the alphabet.

To select the current character, use the arrows icon.

If the result is not as expected, use the Manual segmentation and adjust the

threshold and see the result on the video console or select the character with

the cursor and click on Area Letter<i> button (D) to adjust manually the han-

dles of the training area around the letter.

Increase the Coarse grain limit: reduces accuracy.

Reduce the Fine grain limit: increases accuracy and fine detection.

If some characters are already inside the alphabet, a list

will be displayed and you will be able to select the ones to

add into the alphabet.

If you add a character, it will be linked to the model already

trained and executed if the previous one fails.

Creation procedure

Optical Character Verification

8 - 8 Vision 2007 4.10 User Manual Rev 01

7. To train each character individually, place the

cursor below the character, adjust the area and

use the buttons Add or Replace.

Click on Replace button to replace the existing

character by the current trained character.

Click on

Delete

button to delete the current

trained letter.

Parameters tab

This tab gathers all parameters of the current letter necessary to the running.

Elasticity (A) is the parame-

ter used to determine the de-

gree of tolerance that OCV

will accept for non linearity of

the component. The elasticity

unit is the pixel. Elasticity is

used to stretch or reduce the

size of components in all di-

rections at once. Standard

setting: between 0 and 1.

Scale Min / Scale Max (B)

put the model letter on the letter with a different size. The scale unit is the percent.

Overlap (C) An amount by which model areas can overlap. If models overlap more than

this amount, they are considered to be the same model, and only 1 of them will be re-

turned from a search operation.

Acceptable Score (D) is the minimum score of the model: if the score of the model is

higher than the acceptable score, the letter is found.

Confusion Score (E) is the score from which the algorithm of confusion is launched.

Contrast Threshold (F) is the minimum value of the threshold at which a transition will

be accepted. Contrast is defined by a gray level value.

Area Letter (G) is the size of the trained letter.

The confusion part gathers the confusion letters and the score to find them.

Before testing the string or the char-

acter, define different running param-

eters for each character in the

parameters tab.

Propagation

To propagate the parameters to the others letters, right mouse

click in the value edit box and tick the Data Propagation

menu.

Then, right mouse click in the group box the Propagate menu

and be able to propagate all parameters of the group box.

A Propagation window allows you to select the character

which you want to propagate.

Creation procedure