An image processing apparatus and method for enhancing quality of image data are provided. The image processing apparatus includes an encoder which encodes source image data and outputs compressed image data, a first representative transform coefficient calculator which calculates a first representative transform coefficient by transforming the source image data into frequency characteristics; a decoder which decodes the compressed image data and outputting decoded image data, a second representative transform coefficient calculator which calculates a second representative transform coefficient by transforming the decoded image data into frequency characteristics, and a quality enhancer which enhances the quality of the decoded image data by using the first representative transform coefficient and the second representative transform coefficient.