Huffman codes: piv txwv daim ntawv thov

Thaum lub caij, ob peb cov neeg xav txog qhov tseeb, ua li cas cov ntaub ntawv compression. Muab piv nrog rau yav dhau los siv ntawm tus kheej kev computer tau ua ntau yooj yim dua. Thiab yuav luag txhua tus neeg ua hauj lwm nrog cov ntaub ntawv system siv cov ntaub ntawv. Tab sis ob peb cov neeg xav txog yuav ua li cas lawv ua hauj lwm thiab nyob rau dab tsi hauv paus yog cov ntaub ntawv compression. Cov thawj heev version ntawm tus txheej txheem no yog cov Huffman lis dej num, thiab lawv yuav siv niaj hnub no nyob rau hauv ib tug ntau yam ntawm nrov archivers. Muaj ntau cov neeg siv tsis txawm xav hais tias yuav ua li cas yooj yim ua ntaub ntawv thov compression yuav siv sij hawm qhov chaw thiab nws ua hauj lwm rau ib tug tswvyim. Nyob rau hauv no tsab xov xwm peb saib yuav ua li cas lub compression yog dab tsi nuances pab ceev thiab piv cov txheej txheem ntawm encoding, raws li zoo raws li pom zoo li cas lub hauv paus ntsiab ntawm tsob ntoo coding.

Keeb kwm algorithm

Cov thawj heev algorithm ntawm npaum coding hauv ntaub ntawv tau los ua ib tug code Huffman npaj siab ua thaum ntxov raws li lub nruab nrab ntawm lub thib nees nkaum xyoo pua, namely nyob rau hauv 1952. Nws yog nws leej twg nyob rau lub sij hawm ntawd yog lub puag lub caij ntawm feem ntau ntawm cov kev pab cuam tsim los hlob cov ntaub ntawv. Thaum lub caij, ib qho ntawm feem nrov qhov chaw siv no code yog archives ZIP, ARJ, RAR thiab ntau lwm tus neeg. Tsis tas li ntawd, lub Huffman algorithm yog siv los hlob JPEG-dluab thiab lwm yam duab khoom. Zoo, tag nrho cov faxes kuj siv niaj hnub coding, yees ua nyob rau hauv 1952. Txawm tias muaj tseeb hais tias txij li thaum lub creation ntawm lub code coj li cas lub sij hawm rau hnub no nws yog siv nyob rau hauv ib tug ntau yam ntawm cov tshiab week thiab cov khoom qub thiab niaj hnub hom.

Lub hauv paus ntsiab lus ntawm npaum coding

Lub hauv paus ntawm lub Huffman algorithm muaj xws li ib tug tswvyim uas tso cai rau koj yuav hloov lub feem ntau credible, feem ntau tshwm sim cim cim binary system. Thiab cov neeg uas yog tsis tshua muaj heev, hloov nrog ntev codes. Mus ntev Huffman cov lis dej num tshwm sim tsuas yog tom qab lub system siv rau tag nrho cov yam tsawg kawg nkaus qhov tseem ceeb. Cov txheej txheem no tso cai rau koj kom txo tau qhov ntev ntawm lub chaws rau txhua lub cim piv ntawm cov thawj lus raws li ib tug tag nrho. Qhov tseem ceeb point yog tias nyob rau hauv thaum pib ntawm lub coding yuav tshwm sim ntawm cov tsiaj ntawv yuav tsum tau twb paub. Nws yog los ntawm lawv yuav tsum npaj thiab kev hais lus kawg. Raws li cov ntaub ntawv no, nws nqa tawm kev tsim kho ntawm lub Huffman code tsob ntoo, nyob rau hauv lub hauv paus uas yuav tsum tau muaj cov tsiaj ntawv encoding txheej txheem nyob rau hauv lub archive.

Huffman code, piv txwv li

Muab ua piv txwv lub algorithm, xav txog ib tug graphical variant ntawm kev tsim kho ntawm lub code tsob ntoo. Yuav kom siv cov qauv no yuav tsum tau zoo, nws yog tsim nyog los qhia ntxiv lub ntsiab txhais ntawm ib qhov tseem ceeb tsim nyog rau lub tswvyim ntawm tus txheej txheem. Lub teeb ntawm lub plurality cov ntshav thiab arcs, uas yog qhia los ntawm node rau ntawm, hu ua teeb. Tsob ntoo nws tus kheej yog ib tug teeb nrog ib tug txheej ntawm tej zog:

• nyob rau hauv txhua node tej zaum yuav muaj tsis muaj ntau tshaj li ib tug ntawm cov arcs;
• ib tug ntawm cov ntshav yuav tsum muaj lub hauv paus ntawm tsob ntoo, uas yog, nws yuav tsum tsis txhob yuav ib feem ntawm lub arc ntawm tag nrho cov;
• yog hais tias tus kav pib tsiv raws lub arcs, cov txheej txheem yuav tsum tso cai rau kom tau kiag li nyob rau hauv ib yam ntawm cov ntshav.

Muaj kuj yog xws li ib tug tshaj plaws, ib feem ntawm cov Huffman cov lis dej num raws li ib nplooj ntawm tsob ntoo. Nws yog ib tug ntawm uas yuav tsum tsis txhob mus tej arc. Yog hais tias ob ntshav yog kev cob cog rua ntawm ib tug arc, ib tug ntawm lawv yog cov niam txiv ntawm cov lwm tus me nyuam, nyob ntawm seb ntawm uas ntawm lub arc mus tawm, thiab dab tsi yog muaj. Yog hais tias ob ntshav muaj tib lub niam txiv ntawm, lawv hu ua tus muam qhov chaw. Yog hais tias, nyob rau hauv cov nplooj, tawm los ntawm lub pob hlav ntawm ob peb arcs, ces nws yog hu ua ib tug binary tsob ntoo. Cia li thiaj yog qhov Huffman tsob ntoo. Lub peculiarity ntawm qhov kev siv ntawm cov chav nyob yog tias tus luj ntawm txhua tus niam txiv yog sib npaug zos rau qhov tawm ntawm cov rau tes taw hnyav ntawm tag nrho nws cov me nyuam ntshav.

Ib tug algorithm rau constructing tsob ntoo Huffman

Cov kev siv ntawm lub Huffman code yog tswv yim los ntawm cov tsiaj ntawv ntawm tus niam ntawv. Generated ib daim ntawv teev cov chaw uas yog cov dawb nyob rau hauv lub neej yav tom ntej code tsob ntoo. Tus luj ntawm txhua node nyob rau hauv daim ntawv teev no yuav tsum yog tib yam li qhov yuav tshwm ntawm tshwm sim ntawm cov tsiaj ntawv posts coj mus rau qhov no ntawm. Nyob rau hauv cov ntaub ntawv no, ib tug neeg nyhav qhov tsawg yog xaiv los ntawm cov ob peb free qhov chaw ntawm lub neej yav tom ntej tsob ntoo. Nyob rau hauv cov ntaub ntawv no, yog hais tias tus yam tsawg kawg nkaus cov nqi muaj cai nyob rau hauv ob peb lub chaw, koj yuav dawb do xaiv ib yam ntawm cov officers. Ces los txog rau creation ntawm lub niam txiv ntawm, uas yuav tsum luj kom ntau li ntau raws li lub sum ntawm cov tes taw hnyav li ntawm tus khub cov ntshav. Tom qab ntawd, cov niam txiv xa daim ntawv nrog cov dawb chaw, thiab cov me nyuam raug muab tshem tawm. Nyob rau hauv no arc yog tsim nyog indicators, As, sawv daws yuav thiab zeros. Qhov no tus txheej txheem no rov ntau li ntau raws li yuav tsum tau mus kom tsuas muaj ib zaug xwb node. Ces sau tawm lub binary tug lej tom qab ntawm sab saum toj mus rau nram qab.

Kev txhim kho cov efficiency ntawm compression

Nyob rau hauv thiaj li yuav ua rau kom cov compression efficiency, nws yog tsim nyog thaum lub sij hawm tsob ntoo tsev code siv tag nrho cov ntaub ntawv nyob rau hauv qhov tshwm sim ntawm tshwm sim ntawm cov tsiaj ntawv nyob rau hauv ib qho kev ua ntaub ntawv thov, txuas mus rau ib tsob ntoo, thiab tsis pub qhov tseeb hais tias lawv tawg ri niab tshaj ib tug loj tus naj npawb ntawm cov ntawv luam ntaub ntawv. Yog hais tias lub pre-taug kev los ntawm cov ntaub ntawv no, koj yuav tam sim ntawd xam cov txheeb cais ntawm yuav ua li cas feem ntau muaj cov tsiaj ntawv ntawm lub chaw kawm mus rau lub compression.

Acceleration ntawm lub compression txheej txheem

Kom ceev li lub algorithm, lub ntsiab txhais ntawm cov tsiaj ntawv yuav tsum tau ua tsis nyob rau hauv cov nqe lus ntawm qhov yuav tshwm ntawm tshwm sim ntawm ib tug ntawv, thiab lub zaus ntawm nws tshwm sim. Nrog rau qhov no algorithm yuav yooj yim dua, thiab ua hauj lwm nrog lawv sai npaum li cas. nws kuj txhob ua hauj lwm nrog cov floating-point division. Nyob rau hauv tas li ntawd, ua hauj lwm nyob rau hauv no hom, cov dynamic Huffman code, los yog es lub algorithm nws tus kheej yog tsis raug txog cov kev hloov. Qhov no yog tsuas vim lub fact tias cov probabilities yog ncaj qha xwm yeem mus rau zaus. Nws yog ib nqi hmoog rau lub fact tias cov kawg luj ntawm cov ntaub ntawv, los yog lub thiaj li hu ua cov hauv paus hniav ntawm yog sib npaug zos rau cov sum ntawm tus xov tooj ntawm cov cim nyob rau hauv tus kwv yuav tsum tau kho.

xaus

Huffman cov lis dej num - yooj yim thiab tsim ntev algorithm, uas yog tseem siv los ntawm ntau tus paub zoo tias cov kev pab cuam thiab tuam txhab uas muag. Nws simplicity thiab clarity peev xwm ua tau zoo tau hlob cov ntaub ntawv ntawm tej lub ntim thiab txo qhov chaw nyob rau hauv disk cia. Nyob rau hauv lwm yam lus, lub Huffman algorithm - tau ntev tau soj ntsuam thiab ua hauj lwm daim duab uas cov num yog tsis txo los ntawm hnub no. Thiab nrog lub peev xwm mus tau kom tsis txhob loj ntawm cov ntaub ntawv, hloov lawv ntau tshaj ib tug network los yog los ntawm lwm yam txhais tau tias nws yog ntau yooj yim, ceev thiab yooj yim. Ua hauj lwm nrog cov algorithm, koj muaj peev xwm hlob tej ntaub ntawv kiag li tsis muaj mob rau nws cov qauv thiab zoo, tab sis, nrog lub siab tshaj plaws cov nyhuv rau txo tus luj ntaub ntawv. Nyob rau hauv lwm yam lus, lub coding ntawm lub Huffman code lawm thiab tseem nrov tshaj plaws thiab tseem ceeb txoj kev compressing cov ntaub ntawv loj.