Color-appearance modeling for cross-media image reproduction

Five color-appearance transforms were tested under a variety of conditions to determine which is best for producing CRT reproductions of original printed images. The transforms included: von Kries chromatic adaptation, CIELAB color space, RLAB color appearance model, Hunt\u27s color appearance model, and Nayatani\u27s color appearance model. It was found that RLAB produced the best matches for changes in white point, luminance level, and background changes, but did not accurately predict the effect of surround. The ability of CIELAB color space was equal to that of RLAB in many cases, and performed better for changes in surround. Expert observers generated CRT images in one viewing condition that they perceived to match an original image viewed in another condition. This technique produced images that were equal to or better than the best color appearance model tested and is a useful technique to generate color appearance data for developing new models and testing existing models

Color space selection for JPEG image compression

The Joint Photographic Experts Group\u27s image compression algorithm has been shown to be a very efficient and powerful method of compressing images. However, there is little substantive information about which color space should be utilized when implementing the JPEG algorithm. Currently, the JPEG algorithm is set up for use with any three component color space. The objective of this research was to determine whether or not the color space selected will significantly improve image compression capabilities. The RGB, XYZ, YIQ, CIELAB, CIELUV, and CIELAB LCh color spaces were examined and compared. Both numerical measures and psychophysical techniques were used to assess the results. The final results indicate that the device space, RGB, is the worst color space to compress images. In comparison, the nonlinear transforms of the device space, CIELAB and CIELUV, are the best color spaces to compress images. The XYZ, YIQ, and CIELAB LCh color spaces resulted in intermediate levels of compression

A Study of the color management implementation on the RGB-based digital imaging workflow: digital camera to RGB printers

An RGB (red, green, and blue color information) workflow is used in digital photography today because a lot of the devices digital cameras, scanners, monitors, image recorders (LVT or Light Value Technology), and some types of printers are based on RGB color information. In addition, rapidly growing new media such as the Internet and CD-ROM (Compact Disc-Read-Only Memory) publishing use an RGB -based monitor as the output device. Because color is device-dependent, each device has a different method of representing color information. Each has a different range of color they can reproduce. Most of the time, the range of color, color gamut, that devices can produce is smaller than that of the original capturing device. As a result, a color image reproduction does not match accurately with its original. Therefore, in typical color image reproduction, the task of matching a color image reproduction with its original is a significant problem that operators must overcome to achieve good quality color image reproduction. Generally, there are two approaches to conquer these problems. The first method is trial-and-error in the legacy-based system. This method is effective in a pair-wise working environment and highly depended on a skill operator. The second method is the ICC-based (ICC or International Color Consortium) color management system (CMS) which is more practical in the multiple devices working environment. Using the right method leads to the higher efficiency of a digital photography produc tion. Therefore, the purpose of this thesis project is to verify that ICC-based CMS with an RGB workflow has higher efficiency (better utilized of resource and capacity) than a legacy-based traditional color reproduction workflow. In this study, the RGB workflows from digital cameras to RGB digital printers were used because of the increasing num ber of digital camera users and the advantages of using an RGB workflow in digital pho tography. There were two experimental image reproduction workflows the legacy-based system and the ICC-based color management system. Both of them used the same raw RGB images that were captured from digital cameras as their input files. The color images were modified with two different color matching methods according to each workflow. Then, they were printed out to two RGB digital printers. Twenty observers were asked to evaluate the picture quality as well as the reproduction quality. The results demonstrated that the two workflows had the ability to produce an accept able picture quality reproduction. For reproduction quality aspect, the reproductions of the ICC-based CMS workflow had higher reproduction quality than the legacy-based workflow. In addition, when the time usage of the workflow was taken into account, it showed that the ICC-based CMS had higher efficiency than the legacy-based system. However, many times, image production jobs do not start with optimum quality raw images as in this study; for example, they are under/over exposure or have some defects. These images need some retouching work or fine adjustment to improve their quality. In these cases, the ICC-based CMS with skilled operators can be implemented to these types of production in order to achieve the high efficiency workflow