Recently many techniques have been developed to interconnect different types of color devices : CRT monitors, printers, photographic film and video recorders. It is very important, however, to recognize that the final evaluation of color appearance of an image of any media is performed by the human eye. The CIE colorimetric system is the only color specification system which can relate the spectral radiation information to the visual response. The colorimetric color reproduction is, therefore, the most applicable procedure to interconnect color informations among media. In this tutorial lecture, I talk about the quantitative relationship between the CIE colorimetric system and the human visual system.
Recently the term, "media independent color reproduction", is used. This term shows that the color infomations of television. printing and other media should be interchanged. In such situation, we have a great desire for the transformation of RGB television signal to CMYK pinting signal. But this transformation has many problems. I show the some problems of the transformation from the view of colorimetry.
ISO/TC130 (Graphic Technology) has been reactivated from July 1989 to study and deal with the color electronic prepress requirements of graphic industry. In Japan, Image Processing Technology Standards Committee (IPTS) was inaugurated in April 1988 to study the standardization for graphic technology. The exchange formats for precise color image data, input/output protocol of CEPS and test images are common work items in both committees. This document describes the perceived needs of the test image data and outlines the specifications of the test images.
We propose a systematical color image coding which will be very important in near future image communication via ISDN. The systematic color image coding is systematically designed and coded based on the Picture Quality Scale (PQS). PQS is defined as a function of the color difference which is expected to be defined as an Euclid distance of signal error between the original image signal and the decoded signal. We should start the follwing detailed discussions, (a) the uniformity of HVC color scale, (b) the mathematical two-way transformation between (R, G, B) color space and (H, V, C) color space, (c) the two-war transformation between (R, G, B) color space and (Y, C, M, K) color space. Especially a step of development of VQ codings is considered ; (1) codings of 3-dimensional VQ of Value (V), Chroma (C) and Hue (H), (2) higher dimensional VQ coding considering not only H, V, C but the autocorrelation of sampled image data, and (3) segmentation codings combined with the coding (1). Authors strongly desire that the international friendship should be maintained during the course of the development.
The characteristic of color informations has been investigated from the analysis of the gamut of reproducible colors constructed by 8bits per RGB in Uniform Lightness-Chromaticness color space (HVC). The gamut has been derived from both the linear data and the pre-gamma corrected data used on television system. The feature of colors is examined in HVC space obtained by (R, G, B)→(H, V, C) color space transformation formula. The necessary presicion of quantization is disscussed for high definition image.
Two types of HDTV codecs have been developed aimed at digital transmission of 1125-line/60-Hz HDTV at 155.52 Mbit/s, which is the STM-1 rate of synchronous digital hierarchy. The codecs employ an intrafield/interframe adaptive DCT algorithm and variable word length coding. The coding bit rate for an HDTV signal and 4 sound signals is about 133 Mbit/s. The first type of codec is exclusively used for HDTV bit rate reduction. The second type has a new function called "HDTV/Standard TV compatible coding" where standard definition TV signals as well as HDTV signals can be decoded from the coded HDTV data. Experimental results show these codecs provide sufficient coding performance for HDTV distribution.
High definition high speed videotex prototype system via Broad-band ISDN has been developing. Required key technologies are high speed file access, high speed protocol processing, and high speed display processing. This report describes how we made prototype system software. Aa a result, an HDTV size 24-bit color picture has been gotten within 3 seconds on this system.