CC KHT NIM C BN CA PS CS4

Photoshop ch yu lm vic vi hnh nh dng li im (raster). Do , khi dng Photoshop m cc hnh nh dng vector th Photoshop phi li im ha chng (rasterizer).

I. Hnh nh vector v raster

Hnh nh ha trn my tnh chia lm hai loi: vector v raster.

Hinh nh V ector Hinh nh R aster

c m t bng ng cong hnh hc.

1 e m t bang li diro (raster). Mol diem nh c gol l 1 pixel (picture element) v c gi tri mau (color value) ring cua n.

2 khnsthy i cht lng khi phng to. thu nh.

2. cht lng b| gim khi phnff to hoc th nh nh

3 file dng vector cp dung ung nh 3. file dng raster c duna lcmo n hoc rt ln.

fillusvcaions). iphoiographs) hoc tranh v (pag>.

5 file dng vector thng c u(extension) nh:

CDR (CorelDRAW).AI (Adobe Illustrator) FH(FreeHand)EPS (Encapsulated PostScnpf)

5 file dng raster thng cut(extenswn) nh:

. PSD (Photoshop)TIF (Tag Imaoe File)JPG (Joint Photoaraphic Experts

Group)

II. phn gi nh (image resolution)

phn gii nh l s im nh (pixel) c trn 1 n v chiu di ca hnh nh .

phn gii nh c tnh bng n v ppi (pixels per inch) hoc dpi (dots per inch).

V d: mt hnh nh c kch thc 1 inch X 1 inch v c phn gii 72 ppi s cha tng cng

72 X 72 = 5.184 pixels. Hnh nh c kch thc tng t nhng vi phn gii 300 ppi s cha tng cng 300 X 300 = 90.000 pixels.

Hnh bn tri c phn gii 72 ppi, hnh bn phi 300 ppi

Hnh nh c phn gii cng cao th cng sc nt v mu sc cng chnh xc. V khi , dung lng file cng s tng theo, i hi nhiu b nh v a cng hn.

1. Hnh nh s dng cho thit k web ch cn c phn gii 72 pp.

2. Trng hp hnh nh dng cho thit k ha in n th bn cn nh hai quy tc sau:

Nu l nh nt (line art) hoc n sc (monochrome) th nh nn c phn gii l 1,200 ppi. Neu l nh chp mu (color photograph) hoc nh chp en trng (black and white photograph) th nh nn c phn gii 300 ppi.3. ra nh k thut s th hnh nh cn c phn gii 300 ppi.

4. Nu in nh hi-flex vi kch thc ln ( qung co ngoi tri chng hn) th hnh nh cn c phn gii khong 72 ppi n 100 ppi.

m. Quan h gia kch thc nh v phn gii nh

Hin nay, vic s dng my nh s (digital camera) tr nn rt thng dng, Tuy nhin, hnh nh nhn c t my nh s thng c phn gii 72 pp. Bn nn dng chc nng Image > Image Size ca Photoshop chnh li kch thc nh v phn gii nh cho ph hp vi mc ch ring ca bn.

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VVdth: 19.37 cm Wdth: 30 cm

Hght: 14.49 n 22.45 cm

Resolution: SE3 PfteWnch tosofction: 300 iwels/iKh

S c * Styles Cl Sato StyteComtwt Proportons

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r 'Yesampte Irree:

1 Bcutx (be* for vnoo h M*nt5 8 Sharpen > Unsharp Mask... C 3 phng php ni suy: bicubic, bilinear v nearest neighbor. Phng php bicubic thng cho kt qu tt nht.

* phn gii mn hnh

phn gii mc nhin ca mn hnh (monitor resolution) my Macintosh l 72 dpi, ca mn hnh PC l 96 dpi.

Khi bn chn View > Actual Pixels (Ctrl + 1), Photoshop s hin th hnh nh ch 100%. v l ch trung thc nht ca hnh nh. Khi mi pixel ca hnh nh s c hin th bng mt pixel ca mn hnh.

Khc vi nhng phn mm ha khc, ch hin th 100% khng th hin kch thc tht ca hnh nh. e hnh dung kch thc ca nh khi in ra my in, bn cn chn View > Print Size.

V. Cc ch hnh nh (image modes)

L hnh nh m mi im nh c lun tr bng 1 bit. Nh vy mi im nh ca hnh nh bitmap ch c th l im en hoc im trng. Do , hnh nh dng bitmap chi c 2 sc xm (2 gray levels).

Hnh nh bitmap thng c gi l nh nt.

Mt hnh nh kh A4 (8.26 inch X 11.69 inch) vi phn gii nh 300 ppi, nu c lu tr di ch bitmap s c dung lng file l:

8.26 X 300 X 11.69 X 300 X l b i t = 8.690.346 b i t = 1.086.293 bytes = 1.03 MB

H'mh nh c phn gii 300 dpi, hin th ch 100%

1. Bitmap

Hnh nh bitmap

2. Grayscale

L hnh nh m mi im nh c lu tr bng 8 bit. Nh vy mi im nh ca hnh nh grayscale c th nhn mt gi tr t 0 n 255. Do , hnh nh dng grayscale c 256 sc xm (tc 28).

Nhng nh en trng (black and white photograph) m chng ta thng thy trn bo ch c ch hnh nh l grayscale.

Mt hnh nh kh A4 vi phn gii nh 300 ppi, nu c lu tr di ch grayscale s c dung lng file l:

1.03 MB X 8 = 8.24 MB

Hnh nh grayscale

3. RGB Color

L hnh nh m mi im nh c lu tr bng 24 bits: 8 bits cho mu (Red), 8 bits cho mu lc (Green), 8 bits cho mu lam (Blue). Nh vy mi im nh ca hnh nh RGB c th nhn mt gi tr t 0 n 16.777.216. Do , hnh nh dng RGB c th c n 16,7 triu mu (tc 224).

Nhng nh chp mu (color photograph) t my nh k thut s c ch hnh nh l RGB.

Mt hnh nh kh A4 vi phn gii nh 300 ppi, nu c lu tr di ch RGB s c dung lng file l:

1.03 MB X 24 = 24.72 MB

Nu chn Windows > Channels hin th Channels panel, bn s thy hnh nh RGB c 3 knh mu R, G, B:

Hnh nh RGB c 3 knh mu R, G, B

Hnh nh RGB thng c s dng khi thit k trang web, ra nh k thut s, trnh chiu, x l video...

4. CMYK Color

s dng trong I n cng nghip, hnh nh mu cn c chuyn sang ch CMYK {Cyan, Magenta, Yellow, Black) bng cch chn Image > Mode > CMYK color.

Mi im nh ca hnh nh dng CMYK c lu tr bng 32 bits: 8 bits cho mu lam lc (Cyan), 8 bits cho mu cnh sen (Magenta), 8 bits cho mu vng (Yellow) v 8 bits cho mu en (Black).

Mt hnh nh kh A4 vi phn gii nh 300 ppi, nu c lu tr di ch CMYK s c dung lng file l:

1.03 MB X 32 = 32.96 MB

Hnh nh CMYK c 4 knh mu c, M, Y, K

Surce: Tuoitre Online