Fig. 1. A handwritten page with non-parallel text lines.

Fig. 2. A skewed application form. Such pages with various fonts, both printed and handwritten, and borders usually complicate the skew angle estimation.

Fig. 4. Horizontal histograms of the document page of Fig. 3 for various skew angles.

Fig. 3. A right-oriented document image.

Fig. 5. Maximum peaks of the histograms referred to the document page of Fig. 3, with respect to the skew angle.

Fig. 6. The WVDs for several histograms of the document page of Fig. 3.

Fig. 8. The proposed algorithm.

Fig. 7. The relation between big step and rotations. The required rotations are minimized for a big step equal to 12°.

Fig. 10. The procedure for the handwritten document of Fig. 9(a).

Fig. 9. (a) A skewed handwritten document, (b) after the first estimation, rotated by 60° and (c) after the final estimation rotated by 62.0°.

Fig. 11. Curves of maximum intensity extracted from Fig. 3.

Fig. 12. Number of times that several curves of maximum intensity for different skew angles present maximum.

Fig. 13. A two-column skewed document.

Fig. 14. The horizontal (a) and vertical (b) histogram of the page of Fig. 13.

Fig. 15. The selected part (a) before and (b) after the correction.

Fig. 16. The average maximum intensity curve, the selected threshold and the extracted areas (A, B, and C) of different skew angle for the page of Fig. 1.

Fig. 17. Several curves of maximum intensity for the page of Fig. 1.

Fig. 18. The corrected page of Fig. 1.

Fig. 19. The confidence range of the estimated skew angle vs. the achieved accuracy.

Fig. 20. A skewed document page with a resolution of 100 dpi (a) before and (b) after the correction.

Fig. 21. Skewed page of application form with a resolution of 100 dpi (a) before and (b) after the correction.

Fig. 22. A skewed page of two-column document with a resolution of 100 dpi (a) before and (b) after the correction.

Fig. 23. A skewed page of handwritten document (a) before and (b) after the correction.

Table 1. Experimental data: document images extracted from PS form

Table 2. Performance example for some of the pages shown in this paper