Stage 3. Filters

This is an archived article, no longer relevant.

Use the CapMonster Cloud service to create your own modules. Detailed instructions can be found at this link - Creating a custom module

Graphic filters will help to bring the captcha to the desired color, remove interference, and most importantly - correctly scale the captcha.

What should turn out

Ideally, after applying all filters, your captcha should be:

  1. Black and white without shades of gray. The letters are black, the background is white.

  2. With a minimum amount of clutter such as lines, circles, dots, specks, etc.

  3. Medium size for simple captchas, one and a half to two times larger for more complex captchas.

Two sets of filters

  1. Filters for captchas.

  2. Filters for symbols.

After filtering, captchas and symbols should look the same, i.e. filters for captchas and symbols should be almost the same.

But there are some exceptions, for example, the edge clipping filter is not needed for symbols, only for captchas.

Or, for example, a filter that removes half of the image with a house number in digital ReCaptcha, leaving only the numbers themselves. Obviously, such a filter is not needed to process the collected symbols. Therefore, we had to divide the filters into two groups.

Filters that will definitely come in handy

Thresold filter will make your captcha black and white. Each pixel will turn either black or white, depending on whether it has exceeded a certain threshold. You can set the threshold in the filter setting.

The Resize filter will resize the captcha.

Note that an increase in the size of a captcha leads to an increase in characters on it, and this leads to a forced increase in the character recognition window (in the center of mass search settings), which greatly increases the complexity of the core and, as a result, the total processor time spent on captcha recognition will increase.

Note!

Do not get too carried away with filters to reduce noise.

Video instruction on YouTube link. (in Russian)