Multilayer Reversible Data Hiding Based on the Difference Expansion Method Using Multilevel Thresholding of Host Images Based on the Slime Mould Algorithm

Round 1

Reviewer 1 Report

In this paper, authors proposed a new multi-layered RDH technique through using multi-level thresholding. Based on the thresholds, image pixels were then located and classified. Authors argue that insertion and distortion in the marked image can be decreased after inserting the data by reducing the differences between each class’s pixels. The overall motivation of the article is clear and the innovation points are obvious, but there are still the following concerns:

1. The language needs to continue to be revised, and there are grammatical errors in the manuscript;
2. Considering the large number of letters in the text, it is recommended to create a table to store the key letters and their meanings;
3. The layout of the paper is not aligned, it is recommended to check the overall layout;
4. It is recommended to bold the optimal or own data in the table.

 

 

 

 

 

 

Author Response

The language needs to continue to be revised, and there are grammatical errors in the manuscript;

Response: Thank you for your comment. We checked and improved the language of the whole paper as requested by native speaker research.

Considering a large number of letters in the text, it is recommended to create a table to store the key letters and their meanings;

Response: Thank you for your comment. We added a new table to show the main key in this paper.

The layout of the paper is not aligned, it is recommended to check the overall layout;

Response: Thank you for your comment. We checked the format of the whole paper. Moreover, after the paper got acceptance, the journal will check the format again.

It is recommended to bold the optimal or own data in the table.

Response: Thank you for your comment. Done.

Reviewer 2 Report

In this paper, the authors propose a multi-layered RDH method to to hide data in images. The proposed method leverages SMA to determine the optimal thresholds to be used on the image. Comparison with related works is performed in terms of PSNR, insertion capacity, and processing time.

Major remarks:

1. Section 2 (Prerequisites) should became part of a more detailed section where other related works are described.
2. Formatting of figure 1 needs to be corrected (the numbers inside the table in the upper left corner of the image are not well placed)
3. Section numbers of "Proposed Method" and "Results" are wrong.
4. The caption of figure 5 must be corrected.
5. Eq. 59 must be corrected (check all the equations).
6. According to line 605, Table 1 should contain PSNR results but seems that only insertion capacity is reported.
7. In page 19 (no line numbers are available):
   1. The sentence starting with "The average processing time" is not clear.
   2. Comparison in terms of bits and bpp sems not match with the results showed in Table 1.
8. Text at  the bottom of page 26 (again no line numbers are available) should be merged into the conclusion section.
9. Some sentences are not clear, e.g. the last sentence of the conclusion. (Maybe a punctuation error? Please, check all the paper for similar errors.)

 

Minor remarks:

1. Several line numbers are missing
2. Text formatting can be improved to increase the readability of the paper.
3. Some line numbers (form 171 to 177) overlap with Figure 1.

Author Response

Section 2 (Prerequisites) should became part of a more detailed section where other related works are described.

Response: Thank you for your comment. We make the section one more comprehensive to show a general introduction and the mot related works.

Formatting of figure 1 needs to be corrected (the numbers inside the table in the upper left corner of the image are not well placed)

Response: Thank you for your comment. Done.

Section numbers of "Proposed Method" and "Results" are wrong.

Response: Thank you for your comment. Done. We revised them. Section 1 introduction, Section 2 proposed method, section 3 results, and Section 4 conclusion.

The caption of figure 5 must be corrected.

Response: Thank you for your comment. Done.

Eq. 59 must be corrected (check all the equations).

Response: Thank you for your comment. Done.

According to line 605, Table 1 should contain PSNR results but seems that only insertion capacity is reported.

Response: Thank you for your comment. Done

In page 19 (no line numbers are available):

The sentence starting with "The average processing time" is not clear.

Comparison in terms of bits and bpp sems not match with the results showed in Table 1.

Response: Thank you for your comment. Done. We revised it to be “The average processing time for the proposed method is 173.2367 seconds and for the Arham et al. [3] method is 150.8417 seconds. Therefore, the proposed method is slower than the Arham et al. [3] method, this is due to the use of SMA and its repetitions to obtain optimal thresholds.”

Text at  the bottom of page 26 (again no line numbers are available) should be merged into the conclusion section.

Response: Thank you for your comment. Done.

Some sentences are not clear, e.g. the last sentence of the conclusion. (Maybe a punctuation error? Please, check all the paper for similar errors.)

Response: Thank you for your comment. Done.

 

All the minor issues have been revised

Round 2

Reviewer 2 Report

The authors have addressed most of the comments.

Nevertheless, two issues remain:

1. Eq. 59 must be corrected. Mean Squared Error (MSE) should be squared: (A(i,j) − A(i,j))²

2. The caption of figure 5 must be corrected. In particular, the labels of subfigures a and c are swapped. Now there is written "a) Lena" and "c) Airplane" but they shoul be "a) Airplane" and "c) Lena". The same applies to subfigures d and e.

Author Response

Eq. 59 must be corrected. Mean Squared Error (MSE) should be squared: (A(i,j) − A(i,j))²

^{Thank you for your comment. We revised this given issue.}

The caption of figure 5 must be corrected. In particular, the labels of subfigures a and c are swapped. Now there is written "a) Lena" and "c) Airplane" but they shoul be "a) Airplane" and "c) Lena". The same applies to subfigures d and e.

^{Thank you for your comment. We revised the given figures.}