Lossless Compression: Nws Yog Dab Tsi thiab Yuav Siv Li Cas

by kim Kho tshiab: Lub rau hli ntuj 28, 2022

Kev swb tsis zoo yog lub tswv yim tseem ceeb thaum nws los txog rau digital media. Nws hais txog cov txheej txheem uas cov ntaub ntawv yog compressed tsis muaj kev poob ntawm cov ntaub ntawv. Lossless compression yog ib txoj hauv kev zoo los txo cov ntaub ntawv loj ntawm koj cov xov xwm digital yam tsis muaj kev txi zoo.

Hauv kab lus no, peb yuav tshawb nrhiav

• dab tsi lossless compression yog,
• nws ua haujlwm li cas, Thiab
• yuav ua li cas koj siv tau rau koj kom zoo dua.

Cia peb pib!

Lub ntsiab lus ntawm Lossless Compression

Kev swb tsis zoo yog ib hom ntaub ntawv compression uas khaws cia tag nrho cov ntaub ntawv qub thaum lub sij hawm encoding thiab decoding txheej txheem, xws li qhov tshwm sim yog ib qho tseeb replica ntawm thawj cov ntaub ntawv los yog cov ntaub ntawv. Nws ua haujlwm los ntawm kev nrhiav cov qauv hauv cov ntaub ntawv thiab khaws cia kom zoo dua. Piv txwv li, yog tias ib cov ntaub ntawv muaj 5 lo lus rov qab, tsis txhob khaws cov 5 lo lus duplicate lossless compression yuav khaws cia ib qho piv txwv ntawm cov lus ntawd, ntxiv rau qhov uas nws tuaj yeem nrhiav cov ntaub ntawv hais txog nws cov kev siv hauv cov ntaub ntawv.

Tsis zoo li compression poob (uas muab pov tseg qee cov ntaub ntawv xaiv los txo qhov loj) Lossless Compression tso cai rau koj khaws cia duab daws teeb meem, ntawv clarity thiab cov ntaub ntawv ncaj ncees nrog tsis poob qhov zoo. Qhov no ua rau nws haum rau cov ntawv thov uas qee cov ntaub ntawv tseem ceeb thiab tsis tuaj yeem muab txi rau kev txo qhov loj me. Feem ntau siv rau lossless compression muaj xws li:

• Compressing cov ntaub ntawv suab paj nruag (yog li lub suab zoo yuav tsum nyob twj ywm)
• Nthuav cov duab kho mob (vim cov ntsiab lus me me yuav yog qhov tseem ceeb rau kev kuaj mob)
• Compressing source code ntawm software applications
• Cov ntaub ntawv khaws cia rau lub sijhawm ntev.

Piv txwv ntawm compressors uas tuaj yeem siv hom algorithm no yog ZIP thiab PNG cov ntaub ntawv ib yam li ib co duab tawm tswv yim zoo li TIFF thiab GIF.

Cov txiaj ntsig ntawm Lossless Compression

Kev swb tsis zoo yog ib lub tshuab uas compresses cov ntaub ntawv mus rau hauv ib tug me me me yam tsis muaj kev poob zoo. Qhov no yog ua tau los ntawm kev siv cov algorithms uas txheeb xyuas cov ntaub ntawv tsis tu ncua lossis rov ua cov hlua ntawm cov ntaub ntawv, thiab tom qab ntawd hloov lawv nrog cov lej luv dua. Siv txoj kev no tuaj yeem pab txo qhov loj ntawm cov ntaub ntawv loj, feem ntau los ntawm ib nrab lossis ntau dua, ua kom cov neeg siv khaws cia thiab xa cov ntaub ntawv ntau ntau tau zoo dua.

Ib cag los ntawm kev txuag chaw cia, muaj ob peb lwm cov txiaj ntsig tseem ceeb rau kev siv lossless compression. Cov no suav nrog:

• Kev Ua Zoo Txhim Kho: Lossless compression tuaj yeem txhim kho qhov nrawm ntawm cov ntaub ntawv hloov pauv raws li lawv me dua thiab siv tsawg dua bandwidth thaum xa lossis rub tawm.
• Cov ntaub ntawv ua tiav: Vim tias tsis muaj cov ntaub ntawv poob thaum siv lossless compression, cov ntaub ntawv encoded yuav nyob twj ywm thaum decompression.
• compatibility: Cov ntaub ntawv compressed feem ntau tuaj yeem qhib nrog ntau yam kev siv ntawm ntau lub platform vim nws cov txheej txheem encoding algorithms.
• Txo lub sijhawm ua haujlwm: Txo cov ntaub ntawv loj kom ceev cov txheej txheem xws li luam ntawv, streaming thiab kho raws li cov ntaub ntawv me me yuav tsum tau siv hluav taws xob tsawg.

Hom Lossless Compression

Muaj ntau ntau yam lossless compression cov txheej txheem uas tso cai rau koj mus compress cov ntaub ntawv tsis poob tej ntaub ntawv. Cov feem ntau hom ntawm lossless compression yog ZIP, gzip, thiab LZW. Peb cov no, nrog rau lwm yam ntau yam, txhua tus muaj lawv tus kheej cov txiaj ntsig thiab qhov tsis zoo.

Hauv tsab xov xwm no, peb yuav tham txog ntau hom kev poob qis compression thiab siv lawv li cas:

• ZIP
• gzip
• LZW

Khiav Length Encoding

Khiav Length Encoding (RLE) yog cov ntaub ntawv compression algorithm siv los txo qhov loj ntawm cov ntaub ntawv yam tsis tau poob cov ntaub ntawv. Nws ua haujlwm los ntawm kev txheeb xyuas cov ntaub ntawv, tshawb nrhiav cov cim sib law liag thiab tom qab ntawd muab lawv tso rau hauv ib daim ntawv me me, ntau condensed. Qhov no ua rau cov ntaub ntawv yooj yim khaws thiab xa mus. Thaum lub sij hawm decompression txheej txheem, cov ntaub ntawv qub tuaj yeem rov tsim dua tshiab.

Run Length Encoding feem ntau yog siv rau compressing digital dluab raws li nws zoo txo ​​cov ntaub ntawv redundancy nyob rau hauv cov ntaub ntawv xws li repetitive qauv, khiav ntawm pixels los yog thaj chaw loj uas muaj ib qho xim. Cov ntawv nyeem kuj yog cov neeg sib tw tsim nyog rau RLE compression vim lawv feem ntau muaj cov lus rov qab thiab kab lus.

Khiav Length Encoding yuav siv sij hawm kom zoo dua ntawm qhov tseeb tias ntau cov qauv sib txuas hauv cov ntaub ntawv audio muaj tus nqi zoo ib yam txhawm rau txo lawv qhov loj me tab sis tswj lawv qhov zoo li qub thaum decompression. Qhov no tuaj yeem ua rau txo qis hauv cov ntaub ntawv loj - feem ntau 50% lossis ntau dua - nrog tsawg tsawg poob ntawm lub suab zoo thiab kev ua haujlwm.

Thaum siv RLE encoding, nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias thaum nws zoo li yuav txo cov ntaub ntawv ntau thiab tsawg ntawm cov ntaub ntawv suab lossis cov duab, nws yuav tsis muaj txiaj ntsig zoo rau hom ntawv cov ntaub ntawv uas zoo li tsis muaj ntau qhov rov ua dua vim li cas lawv tau ua raws li kev cai. . Yog li qee qhov kev sim nrog ntau hom kev siv yuav tsim nyog ua ntej txiav txim siab zaum kawg ntawm seb hom kev siv tshuab compression no puas haum rau koj cov kev xav tau.

Huffman Kev Coding

Huffman Kev Coding yog ib qho adaptive, lossless cov ntaub ntawv compression algorithm. Qhov algorithm no siv cov txheej txheem ntawm cov cim cov ntaub ntawv, lossis cov cim, nrog rau lawv qhov xwm txheej ntawm qhov tshwm sim hauv cov ntaub ntawv los tsim cov lej ua ntej. Cov lej no muaj cov lej luv luv uas sawv cev ntau dua cov cim thiab cov lej ntev dua uas sawv cev tsis tshua muaj. Siv cov lej no, Huffman Coding tuaj yeem txo cov ntaub ntawv loj nrog me ntsis cuam tshuam rau nws cov ntaub ntawv ncaj ncees.

Huffman Coding ua haujlwm nyob rau hauv ob kauj ruam: tsim ib txheej ntawm cov cim cim cim thiab siv nws los nthuav cov ntaub ntawv ntws. Cov cim cim feem ntau yog tsim los ntawm lwm cov ntaub ntawv faib tawm ntawm cov cim thiab los ntawm cov ntaub ntawv tau los ntawm kev tshuaj xyuas cov txheeb ze frequencies uas txawv cim tshwm sim nyob rau hauv nws. Feem ntau, Huffman Coding ua haujlwm tau zoo dua li lwm qhov kev poob qis compression algorithms thaum siv cov ntaub ntawv ntws uas muaj cov cim uas muaj. tsis sib npaug ntawm qhov tshwm sim - Piv txwv li, characterizing ib cov ntawv nyeem uas ib co ntawv (zoo li "e") tshwm sim ntau dua li lwm tus (zoo li "z").

Arithmetic Coding

Ib hom lossless compression uas siv tau yog hu ua Arithmetic Coding. Txoj kev no yuav siv sij hawm kom zoo dua ntawm qhov tseeb tias cov kwj ntawm cov ntaub ntawv tuaj yeem muaj qhov tsis txaus ntseeg uas siv qhov chaw, tab sis uas tsis muaj cov ntaub ntawv tseeb. Nws compresses cov ntaub ntawv los ntawm tshem tawm cov redundant seem thaum khaws cia nws cov ntsiab lus tseem ceeb.

Txhawm rau kom nkag siab yuav ua li cas Arithmetic Coding ua haujlwm, cia peb xav txog qhov piv txwv ntawm cov ntawv nyeem. Piv txwv tias muaj plaub lub cim hauv peb cov ntaub ntawv ntws - A, B, C, thiab D. Yog hais tias cov ntaub ntawv raug tso tseg tsis compressed, txhua tus cim yuav siv li yim me ntsis rau tag nrho 32 me ntsis thoob plaws kwj dej. Nrog Arithmetic Coding, txawm li cas los xij, cov txiaj ntsig rov zoo li A thiab B tuaj yeem sawv cev nrog tsawg dua yim ntsis txhua.

Hauv qhov piv txwv no peb yuav siv plaub-ntsis blocks los sawv cev rau txhua tus cim uas txhais tau tias tag nrho plaub lub cim tuaj yeem ntim rau hauv ib qho 16-ntsis thaiv. Tus encoder saib cov kwj ntawm cov ntaub ntawv thiab muab qhov yuav tshwm sim rau txhua tus cim raws li lawv qhov yuav tshwm sim hauv cov hlua txuas ntxiv txhawm rau txhawm rau txuag chaw thaum ua kom qhov tseeb siab tshaj plaws thaum lawv decompressed ntawm lwm qhov kawg. Thaum lub sij hawm compression yog li ntawd tsuas yog cov cim uas muaj peev xwm ntau dua yuav siv tsawg dua thaum cov uas muaj tsawg zaus los yog cov uas tshwm sim tsawg dua yuav xav tau ntau cov khoom ib lub cim thaiv tab sis tseem nyob twj ywm hauv ib qho 16-ntsis thaiv zoo li ua ntej txuag ntau bytes hla tag nrho cov ntaub ntawv kwj thaum piv rau nws uncompressed version.

Yuav Siv Lossless Compression li cas

Kev swb tsis zoo yog ib txoj hauv kev encoding thiab compressing cov ntaub ntawv yam tsis muaj cov ntaub ntawv poob. Txoj kev compression no yog siv los txo qhov loj ntawm cov duab digital, suab, thiab cov ntaub ntawv video. Lossless compression ua rau cov ntaub ntawv khaws cia ntawm ib feem ntawm nws qhov loj me, ua rau cov ntaub ntawv me dua.

Yog li, cia peb nkag mus rau hauv kev nthuav dav thiab tshawb nrhiav yuav ua li cas siv lossless compression:

Cov Ntaub Ntawv Cov Ntaub Ntawv

Kev swb tsis zoo yog ib hom ntaub ntawv compression uas txo cov ntaub ntawv loj yam tsis tau txi ib yam ntawm cov ntaub ntawv uas muaj nyob rau hauv thawj cov ntaub ntawv. Qhov no ua rau nws yog ib txoj hauv kev zoo tshaj plaws rau compressing cov ntaub ntawv loj xws li cov duab digital, audio files, thiab video clips. Txhawm rau siv hom compression no, koj yuav tsum nkag siab txog hom ntaub ntawv uas tau txais kev txhawb los ntawm cov compressors tsis zoo thiab yuav ua li cas los teeb tsa lawv kom zoo rau cov txiaj ntsig zoo.

Thaum compressing ib cov ntaub ntawv rau lossless lub hom phiaj, koj muaj ntau yam kev xaiv rau cov ntaub ntawv tawm tswv yim. Feem ntau yuav, koj yuav xaiv ntawm JPEGs thiab PNGs raws li lawv ob leeg muab cov txiaj ntsig zoo nrog cov ntaub ntawv zoo. Koj kuj tuaj yeem siv hom ntawv zoo li GIF los yog TIFF yog koj software txhawb lawv. Kuj tseem muaj qee qhov tshwj xeeb compressed hom tsim tshwj xeeb rau audio lossis video. Cov no suav nrog FLAC (lossless audio), AVI (lossis video), thiab QuickTime's Kua Lossless hom (ALAC).

Nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias thaum cov hom ntawv no muaj kev compression zoo dua li lawv cov tsis-compressed counterparts, lawv tuaj yeem nyuaj rau kev ua haujlwm nrog vim lawv tsis muaj kev txhawb nqa hauv qee qhov kev siv thiab software program. Nyob ntawm koj qhov teeb tsa, siv uncompressed hom ntawv tej zaum yuav yooj yim dua nyob rau hauv lub sij hawm ntev txawm tias nws yuav siv sij hawm ntau dua qhov chaw disk.

Cov cuab yeej compression

Muaj ntau yam compression cov cuab yeej muaj uas yog tsim los txo qhov loj ntawm cov ntaub ntawv cov ntaub ntawv thaum tswj kev ncaj ncees ntawm cov ntaub ntawv qub. Cov cuab yeej no siv algorithms los txheeb xyuas cov ntaub ntawv rov ua dua thiab muab pov tseg ntawm cov ntaub ntawv yam tsis tau poob cov ntaub ntawv.

Lossless compression yog tshwj xeeb tshaj yog pab tau rau cov duab nraaj, los yog suab thiab video kaw. Cov cuab yeej xws li ZIP, RAR, Stuffit X, GZIP thiab ARJ txhawb ntau theem ntawm kev poob qis rau ntau hom ntaub ntawv suav nrog PDFs thiab compressed executables (EXE). Piv txwv li, yog tias koj compress ib daim duab nrog ib qho ntawm cov qauv no ntawm Qhov siab tshaj plaws txo qhov chaw, koj yuav tuaj yeem qhib thiab saib daim duab ntawd yam tsis tau poob cov ntsiab lus lossis cov ntaub ntawv xim.

Cov algorithm siv yuav cuam tshuam rau cov ntaub ntawv loj uas tuaj yeem ua tiav nrog rau lub sijhawm nws siv los ua cov txheej txheem thiab compress cov ntaub ntawv. Qhov no tuaj yeem nyob ntawm feeb mus rau ob peb teev nyob ntawm seb koj cov cuab yeej xaiv tau zoo npaum li cas. Nrov compression cuab yeej xws li 7-zip (LZMA2) muab cov qib siab compression tab sis xav tau lub sijhawm ua haujlwm ntev dua. Highly optimized cov kev pab cuam zoo li SQ=z (SQUASH) yog cov txheej txheem qis uas tuaj yeem nyem tawm ntxiv bytes ntawm xob laim nrawm piv rau cov ntawv thov nrov dua li Winzip or WinRAR tab sis lawv cov kev nyuaj siab txhais tau tias lawv tsis tshua siv los ntawm cov neeg siv PC amateur.

Kev Pom Duab

Image compression yog ib txoj hauv kev los txo cov ntaub ntawv xav tau los sawv cev rau cov duab digital. Qhov no yog ua los ntawm ob los yog ob qho tib si ntawm ob txoj hauv kev: los ntawm kev tshem tawm lossis txo cov duab tsis tseem ceeb, hu ua lossless compression; lossis los ntawm kev tshem tawm cov ntaub ntawv ceev faj, hu ua compression poob.

nrog lossless compression, cov duab tshwm raws nraim li nws tau ua ua ntej yuav compressed thiab siv tsawg lub cim xeeb cia. Nrog ib compression poob txheej txheem, qee cov ntaub ntawv ploj thaum cov ntaub ntawv tau txais kev cawmdim thiab recompressed tab sis thaum ua kom raug, tsis pom kev cuam tshuam yuav tsum tau pom los ntawm cov ntaub ntawv qub uas tsis tau compressed.

Lossless compression cov tswv yim yog siv dav hauv kev yees duab digital, thiab hauv cov duab tsim ua haujlwm. Lossless cov tswv yim tso cai rau cov ntaub ntawv yuav tsum tau compressed rau ntau qhov me me dua li yog tias lawv tau compressed nrog lwm txoj hauv kev xws li JPEG cov duab uas tsim los rau compression poob qhov twg koj tau txais cov ntaub ntawv me me ntawm tus nqi poob zoo lossis nthuav dav.

Lossless duab hom muaj xws li:

• Hluav taws kub PNGs (ortf)
• GIFs (gif)
• thiab feem ntau siv hom ntawv TIFF (tiff).

Cov duab ua software xws li Photoshop tuaj yeem qhib ntau hom duab thiab hloov lawv mus rau hauv ib qho ntawm cov qauv no siv cov yam ntxwv zoo li "Txuag Raws li" uas yog cov ntaub ntawv ntau npaum li cas hloov dua siab tshiab ntawm hom yam tsis tas yuav rub tawm software ntxiv.

Qee lwm hom duab hom xws li JPEG 2000 (jp2) kuj tseem siv cov txheej txheem compression no txawm li cas los xij lawv muab cov txiaj ntsig ntxiv vim lawv tuaj yeem khaws cov ntaub ntawv ncaj qha ntau dua piv rau JPEGs thaum tseem muaj cov ntaub ntawv me me vim lawv cov txheej txheem coding zoo.

xaus

Kev swb tsis zoo yog lub cuab yeej muaj zog uas tuaj yeem pab koj txo cov ntaub ntawv loj thiab txuag chaw cia, thaum tseem ua kom koj tsis txhob poob cov ntaub ntawv hauv cov txheej txheem. Nws enables koj mus compress cov ntaub ntawv tsis poob ib yam ntawm cov ntaub ntawv uas lawv muaj, ua rau lawv yooj yim rau khaws, nkag mus thiab sib qhia.

Thaum xaus, lossless compression yog ib qho cuab yeej tseem ceeb rau niaj hnub kev khaws cia thiab tswj cov ntaub ntawv.

Summary of Lossless Compression

Kev swb tsis zoo yog ib hom ntaub ntawv compression txheej txheem uas txo cov ntaub ntawv ntau thiab tsawg yam tsis tau txi ib yam ntawm cov ntaub ntawv nyob rau hauv. Nws yog qhov zoo tagnrho rau compressing cov ntaub ntawv raws li cov ntaub ntawv, cov ntawv nthuav qhia, nrog rau cov duab thiab cov ntaub ntawv audio.

Qhov txiaj ntsig tseem ceeb ntawm lossless compression yog nws tso cai rau koj txo qhov loj ntawm cov ntaub ntawv yam tsis muaj kev txi cov ntaub ntawv zoo. Qhov no txhais tau hais tias tib cov ntaub ntawv muaj tseeb tuaj yeem compressed ntau zaus, ua kom yooj yim khaws thiab hloov cov ntaub ntawv loj sai thiab yooj yim. Nws kuj tseem tso cai rau kev siv cia ntau dua los ntawm kev tshem tawm cov ntaub ntawv rov qab los ntawm cov ntaub ntawv thiab khaws cia tsuas yog cov ntsiab lus tseem ceeb ntawm cov ntaub ntawv.

Feem ntau, muaj ob hom lossless compression algorithms - phau ntawv txhais lus raws li algorithms xws li Deflate / GZip lossis Lempel-Ziv (uas compresses cov ntaub ntawv rau hauv daim ntawv teev npe) lossis txoj kev tshem tawm redundancy xws li arithmetic coding los yog khiav ntev encoding (uas tshem tawm redundancy los ntawm encoding rov ua qauv). Txhua hom muaj nws lub hom phiaj tshwj xeeb thaum nws los txog rau hom kev tshaj tawm thiab kev siv.

Rau cov duab, tshwj xeeb tshaj yog, lossless duab hom nyiam PNG yog nyiam dua lwm hom lossy xws li JPEG vim tias lawv khaws cov duab cov ntsiab lus zoo dua li JPEG ua thaum tseem muab cov qib tsim nyog ntawm compression yam tsis muaj qhov cuam tshuam loj rau cov duab zoo lossis nyuaj hauv kev txiav txim siab lossis rov qab cov ntaub ntawv qub. Ib yam li ntawd, digital audio uncompressed waveform cov ntaub ntawv nyiam ua zoo nrog vector quantization cov txheej txheem es tsis yog ntshiab bitrate txo cov txheej txheem.

Nyob rau hauv xaus, lossless compression yog ib txoj hauv kev zoo los txo cov ntaub ntawv loj loj yam tsis muaj kev txi zoo; qhov no ua rau lawv muaj lwm txoj hauv kev khaws cia cov ntaub ntawv tseem ceeb thaum txuag ntawm qhov chaw cia thiab nqi. Raws li kev sib txawv algorithms haum ntau hom kev tshaj tawm zoo dua li lwm tus, nws yog qhov zoo tshaj plaws los ua kev tshawb fawb rau hauv hom twg uas haum rau koj cov kev xav tau rau ob qho tib si kev tiv thaiv ntiag tug thiab qhov chaw ua haujlwm tau zoo - qhov kev xaiv zoo tuaj yeem ua rau txhua qhov sib txawv!

Cov txiaj ntsig ntawm Lossless Compression

Kev swb tsis zoo yog cov ntaub ntawv encoding thiab decoding txheej txheem uas tso cai rau cov ntaub ntawv txuag chaw yam tsis muaj kev txi zoo. Txawm hais tias tus nqi ntawm kev khaws cia tsis tu ncua, kev tswj hwm cov ntsiab lus zoo digital tuaj yeem kim thiab siv sijhawm ntev. Lossless compression algorithms pab txhawb kev khaws cia, kev ua kom zoo hauv lub network, thiab hloov cov ntaub ntawv hla ntau lub tshuab. Tsis tas li ntawd, kev ua kom zoo ntawm cov ntaub ntawv xa mus ceev tuaj yeem txo cov nqi ua haujlwm cuam tshuam nrog kev ua haujlwm I / O thiab pab cov ntaub ntawv tshawb fawb lossis kev kho mob cov chaw soj ntsuam xyuas lawv cov txiaj ntsig tau sai dua.

Qhov zoo ntawm kev siv cov txheej txheem lossless compression muaj xws li:

• Kev txo qis hauv cov ntaub ntawv loj yam tsis qhia txog kev cuam tshuam lossis kev puas tsuaj zoo
• Txhim kho nplooj ntawv nrawm los ntawm kev txo cov ntaub ntawv xa tawm hauv lub vev xaib
• Cov rooj vag qhib cov ntawv thov uas txo cov nqi sib txuas lus kom nkag mus rau cov ntsiab lus ntawm online servers
• Ntxiv archiving peev xwm rau kev khaws cia ntev ntawm cov ntsiab lus digital
• Qhib txoj hauv kev rau kev ntsuas virtual thiab Internet streaming media kev pabcuam los ntawm kev pabcuam cov neeg tuaj saib coob nrog cov peev txheej tsawg kawg nkaus

Nyob zoo, Kuv yog Kim, niam thiab ib tus neeg nyiam nres nrog keeb kwm yav dhau los hauv kev tshaj tawm thiab kev txhim kho lub vev xaib. Kuv muaj kev mob siab rau kev kos duab thiab kev ua yeeb yam, thiab tam sim no kuv tab tom dhia taub hau ua ntej mus rau hauv lub ntiaj teb nres. Nrog rau kuv qhov blog, Kuv tabtom qhia kuv cov kev kawm nrog koj.