Mtundu wa PNG: maonekedwe, ntchito ndi zifukwa za kutchuka

Imodzi mwa ntchito zazikulu zomwe akukumana ndi opanga webusaitiyi atsopano ndikuthamanga mofulumira kwa masamba ndi osatsegula. Ndipo popeza kuti zojambulazo sizingatheke ndi ogwiritsira ntchito onse, tiyenera kuyesayesa pakati pa mapangidwe okongola ndi zokongola zazithunzi ndi liwiro la intaneti. Poyamba, pofuna kuchepetsa kulemera kwa mafano, oyambitsa malo amagwiritsa ntchito GIF kapena JPG. Tsopano, mobwerezabwereza, wordpress imagwiritsa ntchito zithunzi za PNG. Tiyeni tiyesere kumvetsetsa chifukwa chake izi zikuchitika.

Chifukwa chake mawonekedwe a PNG anapangidwa

Chidulecho, chomwe chiri dzina la zithunzizi, chimapangidwa kuchokera ku makalata oyambirira a mawu a Chingelezi otsatirawa: zithunzi zojambula zithunzi, zomwe zingamasuliridwenso ngati "zithunzi zosinthika zomwe zingagwiritsidwe ntchito pa intaneti." Maonekedwe a PNG adakonzedweratu kuti athetse mavuto osokoneza bongo pogwiritsa ntchito GIF algorithm yosavuta, yomwe inayamba kuchepa. Kuonjezerapo, zingatheke kugwiritsidwa ntchito m'malo mwa TIFF yovuta kwambiri, yogwiritsidwa ntchito makamaka pakukonzekera.

Kodi mtundu wa PNG ndi wotani?

Mpaka lero, mawonekedwe awiri a algorithm awa amagwiritsidwa ntchito kwambiri. Pachiyambi choyamba, pulogalamu ya mtundu wa 8-bit ikugwiritsidwa ntchito, ndipo mu yachiwiri, pulogalamu ya mtundu wa 24-bit. Zithunzi mu PNG-8, poyerekeza ndi GIF-version, zimasiyana mosiyana kwambiri ndi kuperewera ndi kusowa kwokhoza kupanga zojambula. Ngakhale kuti fanoli likhoza kukhala ndi maola 256, mawonekedwe awa amagwiritsidwa ntchito kwambiri popanga zojambulajambula, zolemba, mafanizo omwe ali ndi mbali zomveka bwino komanso zithunzi zomwe zimakhala zosaoneka bwino. Nthawi zina izi sizikukwanira, omanga amagwiritsa ntchito 24-bit PNG-format, yomwe ili ndi ubwino wambiri, monga:

• Kulimbitsa machitidwe osokoneza bongo, omwe amanyalanyaza kutayika konse kwa khalidwe.
• Kukhoza kugwiritsa ntchito alpha poyera kumapereka magawo 256 owonetsera.
• Kukhalapo kwa kukonzekera kwa gamma, komwe kumangosintha kuwala kwa chithunzicho pamene mukusewera mu mapulogalamu osiyanasiyana.
• Mphamvu yogwiritsa ntchito zithunzi za mtundu wa 16.7 miliyoni.

Zonsezi palimodzi zimalimbikitsa kugwiritsa ntchito PNG24 chifukwa cha kupanikizika kwa mafano aliwonse okhala ndi malo oonekera, zithunzi ndi mitundu yambiri ya maonekedwe ndi malire omveka a fano.

Chikhalidwe chachitukuko

Ngakhale kuti kugawidwa kwa mawonekedwe a PNG kumatsutsidwa ndi masakatu akale, komanso kusakwanira ndi kosakwanira kuthandizira kwazomwe zamasinthidwe atsopano, mawonekedwe a pawebusaiti PNG ndi odalirika kwambiri. Poyerekeza ndi GIF, ili ndi ubwino waukulu atatu: ma channel alpha, kukonza gamma ndi awiri-dimensional interlacing (njira yopititsira patsogolo chithunzi). Ndipo poyerekeza ndi JPEG alibe kutayika kulikonse. Onani kuti mtundu wa PNG unapangidwa pa January 4, 1995. Kuchokera nthawi imeneyo, zaka 18 zapita, ndipo adayamba kutsogolera njira pogwiritsa ntchito mawebusaiti, kupitiliza GIF kumalo achiwiri. Mapulogalamu ambiri amtundu wamakono (mwachitsanzo MS Paint) lero awalandira ngati mchitidwe wopulumutsa mafayilo "mwachinsinsi". Mwinamwake, ngati sizinali zokhudzana ndi zojambula ndi zolemba zakale za Internet Explorer, GIF ingapereke njira kwa mpikisano wake ngakhale kale.