image processing

A 2-D Butter-worth high-pass filter (BHPF) of order n and cutoff frequency D0 is defined as

An image can be smoothed by attenuating the high-frequency components of its Fourier transform. Because edges and other abrupt changes in intensities are associated with high-frequency components, image sharpening can be achieved in the frequency domain by high pass filtering, which attenuates the low-frequency components without disturbing high frequency information in the Fourier transform. The … Read more

The form of these filters in two dimensions is given by This transfer function is smooth, like Butterworth filter. Gaussian in frequency domain remains a Gaussian in spatial domain Advantage: No ringing artifacts Where D0 is the cutoff frequency. When D(u,v) = D0, the GLPF is down to 0.607 of its maximum value. This means … Read more

Transfer function of a Butterworth lowpass filter (BLPF) of order n, and with cutoff frequency at a distance D0 from the origin, is defined as Transfer function does not have sharp discontinuity establishing cutoff between passed and filtered frequencies. Cut off frequency D0 defines point at which H(u,v) = 0.5

Image compression coding is to store the image into bit-stream as compact as possible and to display the decoded image in the monitor as exact as possible. Now consider an encoder and a decoder as shown in Fig. 1.3. When the encoder receives the original image file, the image file will be converted into a … Read more

Error-free compression techniques usually rely on entropy-based encoding algorithms. The concept of entropy is mathematically described in equation (1): where: a j is a symbol produced by the information source P ( a j ) is the probability of that symbol J is the total number of different symbols H ( z ) is the … Read more

The source encoder reduces or eliminates any redundancies in the input image, which usually leads to bit savings. Source encoding techniques are the primary focus of this discussion. The channel encoder increase noise immunity of source encoder’s output, usually adding extra bits to achieve its goals. If the channel is noise-free, the channel encoder and … Read more

Compression methods can be lossy, when a tolerable degree of deterioration in the visual quality of the resulting image is acceptable or lossless, when the image is encoded in its full quality. The overall results of the compression process, both in terms of storage savings – usually expressed numerically in terms of compression ratio (CR) … Read more