Advantages And Disadvantages Of Discrete Wavelet Transform

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Discrete Wavelet Transform DWT is a frequency based transform which is performed on wavelets. It can be 1-D, 2-D and etc. It divides an image into four sub-bands, namely  LL (Low resolution image)  HL (Horizontal)  LH (vertical)  HH (diagonal) This division can be performed up to many levels. It captures not only notion of frequency content but also temporal content. Wavelets provide a mathematical way of encoding information in such a way that it is layered according to level of detail. DWT is more computationally efficient than other transformations because of its excellent localization properties. Wavelets are capable of complete lossless reconstruction of image[6]. Advantages of DWT 1. No need to divide the input coding into…show more content…
Three levels of rotations have been implemented. First the original watermarked image is being rotated by 90o , then 180o and at last the image is being rotated by 270o in clock wise direction. Gaussian noise On digital image Gaussian noise can be reduced using a spatial filter, though when smoothing an image, an undesirable outcome may result in the blurring of fine-scaled image edges and details because they also correspond to blocked high frequencies. Image compression Image compression may be lossy or lossless. Lossless compression is preferred for archival purposes and often for medical imaging, technical drawings, clip art, or comics. Lossy compression methods, especially when used at low bit rates, introduce compression artifacts. Lossy methods are especially suitable for natural images such as photographs in applications. Salt-and-pepper Noise Salt-and-pepper noise is an attack for which a certain amount of the pixels in the image are either black or white (hence the name of the noise). Salt-and-pepper noise can be used to model defects in the transmission of the image that a pixel is corrupted. Additive
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