Roshan Koju

Work place: Pulchowk Campus, Lalitpur, Nepal



Research Interests: Image Processing, Image Manipulation


Roshan Koju: PHD Research Student in Pulchowk Campus, IOE, TU, Lalitpur, Nepal. He has graduated master’s degree in Computer Engineering from Nepal College of Information Technology, Lalitpur, Kathmandu Nepal, 2011 His research areas include Image processing, Networking, Wireless Communication.

Author Articles
A Semi-Blind Watermarking of Color Images Using Slant Transform, DWT and SVD

By Roshan Koju Shashidhar Ram Joshi

DOI:, Pub. Date: 8 Mar. 2017

This paper presents a robust watermarking for still digital images based on a Slant transform, discrete wavelet transforms and Singular Value Decomposition (SVD). The cover image is transformed using discrete wavelet transform and singular value decomposition while watermark image is transformed using slant transform. It is watermarked by replacing singular values of the high-frequency and low-frequency component of an original image by that of slant transformed watermarks. Experimental results show that our method guarantees the robust resistance against no attack and the robustness against common image processing attacks such as JPEG compression, cropping, histogram equalization, sharpening etc. 

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A LL Subband Based Digital Watermarking in DWT

By Subin Bajracharya Roshan Koju

DOI:, Pub. Date: 8 Mar. 2017

Digital watermarking is a technique which allows an individual to add hidden copyright notices or other verification messages to digital audio, video, image and documents in such a way that the watermark cannot be removed against different attacks. Digital Watermarking is a process to prevent the unauthorized access and modification of data. It ensures that the communication between two parties' remains secure. Digital watermarking can be performed in spatial and frequency domain. In the spatial domain, the watermark is embedded in the very existence of the pixel. In frequency domain, the transformation of any kind is applied and then information is embedded. In this paper, we proposed an approach to watermarking in frequency domain using DWT technique. The gray scale host image is divided into four sub bands: LL, HL, LH, HH and the watermark are inserted in the LL sub band using DWT technique. As the image is divided into four sub bands, a watermark of equal size of the LL sub band is inserted and the results are analyzed on the bases of different parameters such as PSNR and MSE. LL represents the average component of the host image which contains the maximum information of the image. In this approach the watermark is inserted in LL sub band using XOR operation. As the table IV shows, the imperceptibility of this method is quite good. Also, it shows good results when compared with existing methods.

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An Improved DWT-SVD Based Robust Digital Image Watermarking for Color Image

By Subin Bajracharya Roshan Koju

DOI:, Pub. Date: 8 Jan. 2017

The Digital Watermarking Technique has gained its importance due to its ability to provide the secure mechanism for copyright protection and authenticity of the digital data in this high growing internet and computer technology where the tampering and distribution of digital data illegally from unauthorized users is inevitable. For these two important properties of Digital Watermarking, i.e. Robustness and Imperceptibility of watermarked image must take into consideration. In this paper, invisible robust digital watermarking is proposed using Discrete Wavelet Transform and Singular Value Decomposition in YCbCr Color space. The performance of the proposed algorithm is compared with some previous works and results found are more robust against various geometric attacks.

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