1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU T.24 (06/98) SERIES T: TERMINALS FOR TELEMATIC SERVICES Standardized digitized image set ITU-T Recommendation T.24 (Previously CCITT Recommendation) fo+AJ filtre ne modifiant pas la phase da composants IC tra
2、versant ; Fa. 3 - filtre suivi dune ligne B retard (LAR) disper- sive ayant un temps de propagation de groupe TR dcroissant licairement avcc la frkquence f suivant Iexpression : T TR-TO+jo-f)- (avecToT) Af (voir fig. 4). -1 I FIG. 4 telle ligne retard est donne par Et cette phase est bien Ioppod de
3、fJ un dtphasage constant prs (sans importance) et un retard To prs (invitable). Un signal utile S(r) traversant un tel filtre adapt donne la sortie ( un retard To prs et un dpha- sage prs de Ia porteuse) un signal dont in transforme de Fourier est rhlle, constante entre yo et 1128 996 4.70 4.15 2
4、40 1.13 decorative 1410 1245 4.70 4.15 300 1.76 plantings only 1880 1660 4.70 4.15 400 3.13 22 Recommendation T.24 (06/98) - - Figure 19R.24 - House with Trees Figure 20m.24 - House with Sky Recommendation T.24 (06/98) 23 STD * IT-U-T RECMN T.24-ENGL _ 1998 Image Scanned color chart Scanned color ch
5、art Computer- generated color chart generated color chart Kids with toys Computer- generated spheres Graphics art Computer- 7 This set of images comes from the facsimile color test chart (see Figure 21 and Table 6). The toys photo shows higher sharpness for fine detail in the stuffed animals and the
6、 faces, and provides a range of textures and patterns. The presence of both bright and pastel colors provide widespread variations in luminance, hue and saturation. In addition, the image is rich in slowly varying color textures mixed with sharp color boundaries. The computer-generated simulation of
7、 spheres image exhibits shadings for a 3-dimensional effect. It shows various-sized differently-colored spheres on a black background. It provides a wide range of color shadings with distinct edges. In general, each sphere is one color, shaded to give a 3-dimensional appearance. The gradual transiti
8、on in color of each spheres shading provides an excellent medium for discerning possible contouring effects. If contouring is present, it will usually manifest itself as a series of concentric circles with slightly different colors. The spheres edges also provide sharp boundaries against both the ba
9、ckground and other spheres. The graphics image is from a magazine cover and exhibits a 3-dimensional effect. It uses pastel colors to denote surfaces and fine black lines to enhance details. It contains a number of repetitive patterns coupled with sharp boundaries between various colors. T.23 Test C
10、hart No. 6 - 4-Coor Printing Facsimile Test Chart 4CPOl Resolution Sue Color space Pixels Inches (pixeldinch) (MByte (8 bitdcomp.) . (24 bitdpixel) s) Width Height Width Height CIELAB 1688 2347 8.44 11.74 200 1 1.89 CIELAB 3399 4752 8.50 11.88 400 48.46 CIELAB 1752 2375 8.76 11.88 200 12.49 CIELAB 3504 4750 8.76 11.88 400 49.94 CIELAB 3242 3656 8.11 9.14 400 35.56 CIELAB 1024 512 2.56 1.28 400 1.58 CIELAB 2644 3046 6.61 7.62 400 24.17 Table 6ff .24 - Color Images Figure number Figure 21 Figure 21 Figure 21 Figure 21 ! i Figure 21 I Dimensions -1- I 24 Recommendation T.24 (06/98)
