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4. Mass centers

Setting mass centers - is one of the most important steps of creating your own recognition module. Mass centers will be set on captcha images as green (by default) dots. They indicate the area of symbol search. At this step you will also need to set size of symbol recognition frame.

Main aim

You should set mass centers in the following way:

1) The dots should pass through the centers of letters or as close as possible.
2) You should set as less dots as possible. But not less than required:)
3) Displayed counting time should not be too high.

1) Symbol recognition frame size
Frame size should cover the largest symbol in captcha. Click on captcha image and green frame will appear.Adjust this frame to fit the largest symbol.
2) Mass count field size
Increasing width you make mass centers line more smooth and vice versa. Mass centers line should go through symbols centers but do not jog on them. Height should be set to get only one line on symbol.
3) Recognition threshold
Adjust recognition threshold in the way to reduce mass centers line, but not to remove it from symbols centers.
4) Symbol threshold
Leave this paramater as default.
5) Not more than one check point for this rectangle
It is not necessary to search for symbol by width. You can search by 2 points if captcha is small, or by 3-4 points if captcha is large. Height parameter should be a little higher than height of the largest symbol. Or even more high, if you have one-line captcha. If you set too much points, it will slow down recognition process. And if you set to high variation, you may get many recognition errors.

Different types of captcha

Captchas may contain closely set symbols or separate symbols. In the first case, after setting mass centers, if you did everything correctly, they should look like a green line, which passes through symbol centers. In the second case, there should be green dots in center of every symbols.

After training recognition core

On this tab you may also make some LBM clicks to check core response in some captcha image areas, to identify where may be recognition errors.

Draw your attention

When adjusting mass centers search setting, it is recommended to flick through captcha images and check how they work on several images, not only on the one.

en/addons/capmonster/learning/center-mass-finder.txt · Last modified: 2015/10/15 13:07 by vladz