# Analysis of Recent Deep Learning Techniques for Arabic Handwritten-Text OCR and Post-OCR Correction
## 3 Arabic OCR Challenges
### Arabic OCR Challenges [19; 20; 21]  
1. Arabic is written from right to left, while most models are more used to the opposite direction;
2. Arabic consists of a minimum of 28 characters, and each character has a minimum of two and up to four shapes, depending on the position. Fortunately, no upper- or lower-case characters are used in Arabic;
3. The position determines the shape of a character. Therefore, a character can have different shapes depending on its position: alone, at the start, in the middle, or at the end. For example, the letter Meem has different shapes according to its position;
4. Ijam: Dots can be written above or below characters, and they differentiate between one character and another, such as Baa and Tha;
5. Tashkeel: Marks such as Tanween and Harakat can change the context of a piece of writing. Examples applied to the letter Raa are illustrated in Table 1;  
Hamza, in various locations, such as above or below Alif, above Waw, after or above Yaa, and in the middle or end of a word;
7. Loops, such as Saad and Taa, and Meem and Ain, where the difference between characters is difficult to distinguish due to the similarity of the skeleton;
8. Separated characters separate words, such as Raa, Dal, and Waw. Figure 5 presents an example with different kinds of separation;  
One sub-word:  
Two sub-words:  
Three sub-words:  
Four sub-words:  
Five sub-words:  
The total number of shapes is at least 81. Some letters share the same shape but differ in terms of dots;  
Without dots, there are at least 52 letter shapes;  
The structural characteristics of the characters, given their high similarity in shape, can be perplexing. Moreover, a slight modification can turn one character into another;  
Arabic is cursively written. Therefore, connections are formed when two characters are connected;  
The presence of other diacritics, such as Shadda, and punctuation, such as full stops can be confused with the dots that are used in Arabic;  
Most models suffer from overfitting, since generalization is not a concern, partly because of the lack of annotated datasets and partly because complex models are trained on small sets or sets that are not balanced;  
The available datasets have the issue of distorted and unclear samples;  
\begin{table} \begin{tabular}{c c c c c c c c} \hline \hline
**Fatha** & **Fathatain** & **Dammah** & **Dammatian** & **Kasra** & **Kasratian** & **Sukoon** & **Shaddah** \\ \hline \(\hat{j}\) & \(\hat{j}\) & \(\hat{j}\) & \(\hat{j}\) & \(\hat{j}\) & \(\hat{j}\) & \(\hat{j}\) & \(\hat{j}\) \\ \hline \hline \end{tabular}   
* 6. Hamza, in various locations, such as above or below Alif, above Waw, after or above Yaa, and in the middle or end of a word;
* 7. Loops, such as Saad and Taa, and Meem and Ain, where the difference between characters is difficult to distinguish due to the similarity of the skeleton;
* 8. Separated characters separate words, such as Raa, Dal, and Waw. Figure 5 presents an example with different kinds of separation;  
One sub-word:  
Two sub-words:  
Three sub-words:  
Four sub-words:  
Five sub-words:  
The total number of shapes is at least 81. Some letters share the same shape but differ in terms of dots;  
Without dots, there are at least 52 letter shapes;  
The structural characteristics of the characters, given their high similarity in shape, can be perplexing. Moreover, a slight modification can turn one character into another;  
Arabic is cursively written. Therefore, connections are formed when two characters are connected;  
The presence of other diacritics, such as Shadda, and punctuation, such as full stops can be confused with the dots that are used in Arabic;  
Most models suffer from overfitting, since generalization is not a concern, partly because of the lack of annotated datasets and partly because complex models are trained on small sets or sets that are not balanced;  
The available datasets have the issue of distorted and unclear samples;  
Figure 5: Elucidation of how sub-words are formed in Arabic.