PERBANDINGAN HASIL WATERMARKING PADA CITRA DIGITAL DENGAN METODE DISCRETE WAVELET TRANSFORM DAN DISCRETE COSINE TRANSFORM

Pesatnya perkembangan internet dalam beberapa tahun terakhir telah dengan cepat meningkatkan ketersediaan data digital seperti audio, gambar, dan video ke publik. Permasalahan mengenai perlindungan informasi multimedia menjadi semakin penting. Banyak pemilik hak cipta khawatir dalam melindungi data digital yang mereka miliki terhadap duplikasi ilegal. Dari sekian banyak pendekatan yang mungkin dilakukan untuk melindungi hak cipta pada multimedia, watermarking adalah salah satu yang paling diminati. Gagasan watermarking pada citra digital adalah dengan menanamkan data informasi ke dalam citra tanpa terdeteksi sistem penglihatan manusia tetapi tetap terlindungi dari berbagai serangan operasi pemrosesan gambar. Metode watermarking yang digunakan dalam penelitian ini adalah metode Discrete Wavelet Transform (DWT) dan Discrete Cosine Transform (DCT). Metode DWT dilakukan dengan mendekomposisi citra menjadi 4 sub-band, dan metode DCT dilakukan dengan membagi citra ke dalam blok 8x8. Kedua metode tersebut digunakan dengan tujuan untuk membandingkan kemampuan masing-masing metode dalam melindungi hak cipta citra digital. Hasil penelitian menunjukkan bahwa watermark yang dihasilkan dengan menggunakan metode DWT dapat tersisipkan dengan baik sehingga tidak terlihat secara kasat mata (imperceptible) dibandingkan dengan metode DCT. Namun, untuk tingkat ketahanan watermark terhadap gangguan berupa operasi pemrosesan citra, metode DCT menghasilkan kualitas watermark yang lebih robust dan baik. The rapid expansion of the internet in the past years has rapidly increased the availability of digital data such as audio, images and videos to the public. The problem of protecting multimedia information becomes more and more important and a lot of copyright owners are concerned about protecting any illegal duplication of their data or work. Of the many approaches possible to protect visual data, digital watermarking is probably the one that has received most interest. The idea of digital image watermarking is to embed information data within the image with an insensible form for human visual system but in a way that protects from attacks such as common image processing operations. The watermarking method used in this study is the Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT) methods. The DWT method is done by decomposing the image into 4 sub-bands, and the DCT method is done by dividing the image into 8x8 blocks. Both methods are used with the aim of comparing the ability of each method to protect digital image copyright. The results showed that the watermark generated using the DWT method can be inserted properly so it is not visible invisible (imperceptible) compared to the DCT method. However, for the level of watermark resistance to disturbances in the form of image processing operations, the DCT method produces a more robust and better quality watermark

An enhanced method based on intermediate significant bit technique for watermark images

Intermediate Significant Bit digital watermarking technique (ISB) is a new approved technique of embedding a watermark by replacing the original image pixels with new pixels. This is done by ensuring a close connection between the new pixels and the original, and at the same time, the watermark data can be protected against possible damage. One of the most popular methods used in watermarking is the Least Significant Bit (LSB). It uses a spatial domain that includes the insertion of the watermark in the LSB of the image. The problem with this method is it is not resilient to common damage, and there is the possibility of image distortion after embedding a watermark. LSB may be used through replacing one bit, two bits, or three bits; this is done by changing the specific bits without any change in the other bits in the pixel. The objective of this thesis is to formulate new algorithms for digital image watermarking with enhanced image quality and robustness by embedding two bits of watermark data into each pixel of the original image based on ISB technique. However, to understand the opposite relationship between the image quality and robustness, a tradeoff between them has been done to create a balance and to acquire the best position for the two embedding bits. Dual Intermediate Significant Bits (DISB) technique has been proposed to solve the existing LSB problem. Trial results obtained from this technique are better compared with the LSB based on the Peak Signal to Noise Ratio (PSNR) and Normalized Cross Correlation (NCC). The work in this study also contributes new mathematical equations that can study the change on the other six bits in the pixel after embedding two bits