Raster Images vs. Vector Graphics
Computer graphics can be created as either raster or vector images. Raster graphics are bitmaps. A bitmap is a grid of individual pixels that collectively compose an image. Raster graphics render images as a collection of countless tiny squares. Each square, or pixel, is coded in a specific hue or shade. Individually, these pixels are worthless. Together, they’re worth a thousand words.
Raster graphics are best used for non-line art images; specifically digitized photographs, scanned artwork or detailed graphics. Non-line art images are best represented in raster form because these typically include subtle chromatic gradations, undefined lines and shapes, and complex composition.
However, because raster images are pixel-based, they suffer a malady called image degradation. Just like photographic images that get blurry and imprecise when blown up, a raster image gets jagged and rough. Why? Ultimately, when you look close enough, you can begin to see the individual pixels that comprise the image. Hence, your raster-based image of Wayne Newton, magnified to 1000%, becomes bitmapped before you can isolate that ravenous glint in his eye. Although raster images can be scaled down more easily, smaller versions often appear less crisp or “softer” than the original.
To maximize the quality of a raster image, you must keep in mind that the raster format is resolution-specific — meaning that raster images are defined and displayed at one specific resolution. Resolution in raster graphics is measured in dpi, or dots per inch. The higher the dpi, the better the resolution. Remember also that the resolution you actually observe on any output device is not a function of the file’s own internal specifications, but the output capacity of the device itself. Thus, high resolution images should only be used if your equipment has the capability to display them at high resolution.
Better resolution, however, comes at a price. Just as raster files are significantly larger than comparable vector files, high resolution raster files are significantly larger than low resolution raster files. Overall, as compared to vector graphics, raster graphics are less economical, slower to display and print, less versatile and more unwieldy to work with. Remember though that some images, like photographs, are still best displayed in raster format. Common raster formats include TIFF, JPEG, GIF, PCX and BMP files. Despite its shortcomings, raster format is still the Web standard — within a few years, however, vector graphics will likely surpass raster graphics in both prevalence and popularity.
Unlike pixel-based raster images, vector graphics are based on mathematical formulas that define geometric primitives such as polygons, lines, curves, circles and rectangles. Because vector graphics are composed of true geometric primitives, they are best used to represent more structured images, like line art graphics with flat, uniform colors. Most created images (as opposed to natural images) meet these specifications, including logos, letterhead, and fonts.
Inherently, vector-based graphics are more malleable than raster images — thus, they are much more versatile, flexible and easy to use. The most obvious advantage of vector images over raster graphics is that vector images are quickly and perfectly scalable. There is no upper or lower limit for sizing vector images. Just as the rules of mathematics apply identically to computations involving two-digit numbers or two-hundred-digit numbers, the formulas that govern the rendering of vector images apply identically to graphics of any size.
Further, unlike raster graphics, vector images are not resolution-dependent. Vector images have no fixed intrinsic resolution, rather they display at the resolution capability of whatever output device (monitor, printer) is rendering them. Also, because vector graphics need not memorize the contents of millions of tiny pixels, these files tend to be considerably smaller than their raster counterparts. Overall, vector graphics are more efficient and versatile. Common vector formats include AI, EPS, CGM, WMF and PICT (Mac).
Picha za Raster dhidi ya Picha za Vector Picha za kompyuta zinaweza kuundwa kama picha za raster au vector. Picha za raster ni ramani za bit. Bitmap ni gridi ya pixels binafsi ambayo kwa pamoja kuunda picha. Picha za raster huonyesha picha zikiwa mkusanyiko wa mraba wadogo usiohesabika. Kila mraba, au pixel, imeandikwa kwa rangi au kivuli hususa. Kila moja ya pikseli hizo haina thamani. Pamoja, zina thamani ya maneno elfu moja. Raster graphics ni bora kutumika kwa ajili ya non-line sanaa picha; hasa digitized picha, scanned kazi ya sanaa au graphics kina. Picha za sanaa zisizo za mstari zinawakilishwa vizuri katika fomu ya raster kwa sababu hizi kwa kawaida ni pamoja na gradations subtle chromatic, mistari isiyojulikana na maumbo, na muundo tata. Hata hivyo, kwa sababu picha za raster zinategemea pikseli, zinateseka kutokana na ugonjwa unaoitwa uharibifu wa picha. Sawa na picha za picha ambazo huwa zisizo wazi na zisizo sahihi zinapopandishwa, picha ya raster huwa na kasoro na mbaya. Kwa nini? Hatimaye, unapoangalia kwa karibu vya kutosha, unaweza kuanza kuona pikseli za mtu binafsi ambazo hufanyiza picha. Kwa hiyo, picha yako ya raster ya Wayne Newton, iliyoongezwa kwa 1000%, inakuwa na ramani ya bit kabla ya kuweza kutenganisha mwangaza huo wa njaa katika jicho lake. Ingawa picha raster inaweza kuwa scaled chini kwa urahisi zaidi, matoleo madogo mara nyingi kuonekana chini crisp au <unk>softer<unk> kuliko ya awali. Ili kuongeza ubora wa picha ya raster, lazima kukumbuka kwamba muundo wa raster ni azimio maalum <unk> maana kwamba picha raster ni kufafanuliwa na kuonyeshwa katika azimio moja maalum. Ufafanuzi katika picha za raster hupimwa katika dpi, au nukta kwa inchi. Kadiri dpi ilivyo juu, ndivyo azimio linavyokuwa bora. Kumbuka pia kwamba azimio wewe kweli kuchunguza juu ya kifaa chochote pato si kazi ya faili mwenyewe maalum ya ndani, lakini uwezo wa pato la kifaa yenyewe. Hivyo, picha za azimio la juu zinapaswa kutumika tu kama vifaa vyako vina uwezo wa kuionyesha kwa azimio la juu. Hata hivyo, kuna gharama ya kupata azimio bora zaidi. Kama vile faili raster ni kubwa sana kuliko faili vector kulinganisha, faili raster azimio la juu ni kubwa sana kuliko faili raster azimio la chini. Kwa ujumla, ikilinganishwa na graphics vector, graphics raster ni chini ya kiuchumi, polepole kuonyesha na kuchapisha, chini ya versatile na zaidi unwieldy kufanya kazi na. Kumbuka ingawa kwamba baadhi ya picha, kama picha, bado ni bora kuonyeshwa katika muundo raster. Raster ni aina ya faili ya raster ya kawaida, pamoja na faili za TIFF, JPEG, GIF, PCX, na BMP. Licha ya mapungufu yake, muundo wa raster bado ni kiwango cha Mtandao <unk> ndani ya miaka michache, hata hivyo, picha za vector zinaweza kuzidi picha za raster katika kuenea na umaarufu. Tofauti na picha za raster za pixel, picha za vector zinategemea formula za hisabati ambazo hufafanua primitives za kijiometri kama vile polygons, mistari, curves, duru na rectangles. Kwa sababu vector graphics ni pamoja na kweli geometric primitives, wao ni bora kutumika kuwakilisha picha zaidi muundo, kama line sanaa graphics na gorofa, rangi sawa. Picha nyingi zilizotengenezwa (kinyume na picha za asili) zinakidhi vipimo hivi, ikiwa ni pamoja na nembo, kichwa cha barua, na fonti. Inherently, vector-msingi graphics ni zaidi malleable kuliko picha raster <unk> hivyo, wao ni mengi zaidi versatile, kubadilika na rahisi kutumia. Faida dhahiri zaidi ya picha vector juu ya picha raster ni kwamba picha vector ni haraka na kikamilifu scalable. Hakuna kikomo cha juu au cha chini kwa ukubwa wa picha vector. Kama vile sheria za hisabati zinatumika kwa hesabu zinazohusisha tarakimu mbili au tarakimu mia mbili, formula zinazosimamia uwasilishaji wa picha za vector zinatumika kwa picha za ukubwa wowote. Zaidi ya hayo, tofauti na picha raster, picha vector si azimio-kutegemea. Picha za vector hazina azimio la ndani la kudumu, badala yake zinaonyesha uwezo wa azimio la kifaa chochote cha pato (mfuatiliaji, printa) kinachowatoa. Pia, kwa sababu graphics vector hawana haja ya kukumbuka maudhui ya mamilioni ya pixels ndogo, faili hizi huwa na kuwa kiasi kidogo kuliko wenzao raster. Kwa ujumla, vector graphics ni ufanisi zaidi na versatile. Vector format ni pamoja na AI, EPS, CGM, WMF na PICT (Mac).