This document summarizes image compression techniques. It discusses how image compression aims to reduce the number of bits required to represent an image by removing spatial and spectral redundancies. The techniques are classified as lossless or lossy. Lossy techniques discussed include discrete cosine transform coding, discrete wavelet transform coding, vector quantization, fractal coding, and block truncation coding. Key metrics for evaluating compression performance and quality, such as mean square error and peak signal-to-noise ratio, are also defined.