Image Compression Using Hybrid(DCT+DWT) Technique- A Comparative Study

When the data is in uncompressed state it becomes difficult to store and transmit it. This problem can be addressed by image compression. Image compression reduces the number of bits per pixel of the image so that its storage and transmission becomes easy. Basic goal of image compression is to increase visual quality of image with less noise. The proposed methodology satisfies this aim. Hybrid of DCT (Discrete Cosine Transformation) and DWT (Discrete Wavelet Transformation) are combined to achieve this goal. Combined advantages of DCT and DWT are used as proposed methodology. DCT has high energy compaction and less number of computational resources are required while DWT has multi resolution transformation. Hybrid DCT-DWT is proposed to compress and reconstruct images. Also colorization of the reconstructed images is proposed. Reconstructed images are stored in gray format and to visualize it colorization is done on that gray scale image. Results show that this method of compression and colorization helps in compressing and retaining color of images

Survey of Hybrid Image Compression Techniques

A compression process is to reduce or compress the size of data while maintaining the quality of information contained therein. This paper presents a survey of research papers discussing improvement of various hybrid compression techniques during the last decade. A hybrid compression technique is a technique combining excellent properties of each group of methods as is performed in JPEG compression method. This technique combines lossy and lossless compression method to obtain a high-quality compression ratio while maintaining the quality of the reconstructed image. Lossy compression technique produces a relatively high compression ratio, whereas lossless compression brings about high-quality data reconstruction as the data can later be decompressed with the same results as before the compression. Discussions of the knowledge of and issues about the ongoing hybrid compression technique development indicate the possibility of conducting further researches to improve the performance of image compression method

Mathematical transforms and image compression: A review

It is well known that images, often used in a variety of computer and other scientific and engineering applications, are difficult to store and transmit due to their sizes. One possible solution to overcome this problem is to use an efficient digital image compression technique where an image is viewed as a matrix and then the operations are performed on the matrix. All the contemporary digital image compression systems use various mathematical transforms for compression. The compression performance is closely related to the performance by these mathematical transforms in terms of energy compaction and spatial frequency isolation by exploiting inter-pixel redundancies present in the image data. Through this paper, a comprehensive literature survey has been carried out and the pros and cons of various transform-based image compression models have also been discussed