Investigating the relationship between image enhancement and image compression in the context of the multi-scale retinex

Image enhancement and data compression methods arose from the distinct and largely separate disciplines of image processing and communications respectively, yet both are important components of current and future digital imaging systems technology. Here we examine the relationship of these two components with special emphasis on image enhancement and lossy jpeg image compression. When transmission channel capacity is limited, image/data compression is often performed to increase the data throughput. However, this compression has a significant impact on the quality of the final data that is received. In most cases, image enhancement performed after image compression tends to bring out the artifacts injected into the data due to the compression. However, if image enhancement is performed before image compression, there are two issues that arise: (i) image enhancement typically increases the contrast—amount of observable detail—in an image which leads to poorer compression ratios; and (ii) the radiometric information in the original data is typically irretrievably lost. In this paper we address the impact of image enhancement, specifically that of the multi-scale retinex with color restoration (msrcr) on image compression, and vice versa. We also look at the impact of compression on recovering original data from enhanced imagery given certain parameters about the enhancement process. In this context, we also develop an inversion process for the msrcr.

Research highlights
► End-to-end systems analysis of image enhancement and lossy JPEG compression is examined.
► Order of enhance-compress is examined.
► Enhance-compress order is recommended.
► Impact of enhance-compress order is to require a lower JPEG Quality Factor for a given compression ratio.
► This, however, does result in overall better image quality output compared to compress-enhance order.