Table 5.
Summarized view of various pre-processing techniques.
| S. No. | Year and Reference | Operation Performed |
|---|---|---|
| 1. | 2013 [37] | anisotropic diffusion |
| 2. | 2015 [57] | image smoothing, clipping, histogram equalization, image enhancement, and color conversion |
| 3. | 2015 [58] | resizing and cropping |
| 4. | 2016 [38] | resizing, denoising |
| 5. | 2016 [8] | resizing and cropping |
| 6. | 2017 [59] | clipping, smoothing, image enhancement |
| 7. | 2018 [61] | size reduction and cropping |
| 8. | 2018 [5] | image enhancement, CIELAB color space |
| 9. | 2019 [62] | resizing and cropping |
| 10. | 2019 [63] | downsize images, improve contrast, and transform RGB images into greyscale |
| 11. | 2019 [7] | RGB format images into grayscale |
| 12. | 2019 [18] | enhancing compactness, changing brightness, extracting noise, and converting to another color space |
| 13. | 2019 [47] | resizing operation |
| 14. | 2020 [51] | downscaled to a lower resolution, contrast enhancement |
| 15. | 2021 [30] | resizing and normalization |
| 16. | 2021 [32] | resizing and denoising |
| 17. | 2021 [65] | resizing, restoration, and image enhancement |
| 18. | 2021 [1] | image resizing and image restoration |
| 19. | 2022 [66] | denoising |