**4. Experiment techniques**

In the conducted experiments, six different OCRs were used to test the technical performance of the proposed CAPTCHA techniques. The used OCRs have a good review from some technical experts and they provide good results when used to extract the regular text.

Moreover, other methods were used to test the usability, such as surveys and local web pages to get the users' responses and analyze them from different perspectives.

#### **4.1. First OCR**

The first OCR used in the experiments is an application called Free OCR. This application utilizes the most recent version of the Tesseract OCR engine (v3.01), which can ensure a reliable level of text-extracting accuracy. Tesseract is an open-source OCR engine maintained by Google. It offers support for different languages, with a level of accuracy potentially reaching 98% [1, 5].

#### **4.2. Second OCR**

Capture2Text is the second technique used in our experiments. It is an open-source OCR tool, like the first OCR; it uses the Tesseract engine introduced by Google to capture the written text in images and then copies it to the clipboard.

#### **4.3. Third OCR**

The third OCR used is a free online OCR called i2OCR. It is available in the following link: http://www.i2ocr.com/. This online OCR supports various recognition languages; it also has the ability to extract text from various columns in the images.

#### **4.4. Fourth OCR**

FreeOCR is the fourth OCR tool used in the experiments. As the name suggests, it is available online as a free service, which is available in the following link: http://www.free-ocr.com/. Moreover, the extraction process speed for this OCR site is considered fast in comparison with other online OCRs, and it produces the extracted text fairly quickly [6].

#### **4.5. Fifth OCR**

As shown above, when the CAPTCHA word is generated, it is displayed to the user in one of adopted languages (Arabic, English, French, and Spanish). **Figures 5**–**8** show examples of the

handwritten CAPTCHA technique with each adopted language.

**Figure 4.** CAPTCHA word construction process.

168 Multilingualism and Bilingualism

**Figure 5.** English CAPTCHA "M u J F R t Q".

**Figure 6.** French CAPTCHA "F ë x Œ r".

**Figure 7.** Spanish CAPTCHA "X b CH y N R w".

The fifth OCR we adopted in the experiments is an online OCR software called OnlineOCR.This OCR software is available in the following link: http://www.onlineocr.net/. Additionally, this OCR software supports 46 recognition languages and it is able to extract texts in any of these languages. It also can detect text written in more than one language in the same image or document.

### **4.6. Sixth OCR**

NewOCR is a free online OCR service that we used as the sixth technique in our experiments. The NewOCR service is available in the following link: https://www.newocr.com/. This online service supports more than 100 recognition languages and different fonts supports. In addition, the NewOCR service works using Tesseract OCR engine which is considered the best accurate OCR engine available at this time. It also supports the low-resolution images and can extract the text written in these images.
