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[{"key": "dc.contributor.author", "value": "Ollari, Ilkka", "language": null, "element": "contributor", "qualifier": "author", "schema": "dc"}, {"key": "dc.date.accessioned", "value": "2010-08-27T05:54:44Z", "language": null, "element": "date", "qualifier": "accessioned", "schema": "dc"}, {"key": "dc.date.available", "value": "2010-08-27T05:54:44Z", "language": null, "element": "date", "qualifier": "available", "schema": "dc"}, {"key": "dc.date.issued", "value": "2010", "language": null, "element": "date", "qualifier": "issued", "schema": "dc"}, {"key": "dc.identifier.other", "value": "oai:jykdok.linneanet.fi:1134642", "language": null, "element": "identifier", "qualifier": "other", "schema": "dc"}, {"key": "dc.identifier.uri", "value": "https://jyx.jyu.fi/handle/123456789/24906", "language": null, "element": "identifier", "qualifier": "uri", "schema": "dc"}, {"key": "dc.description.abstract", "value": "Digitaalisten valokuvien muokkaamisesta on tullut hyvin helppoa ja yleist\u00e4, mik\u00e4 on nostanut esille huolen valokuvien uskottavuudesta. Ongelman ratkaisuksi on esitetty erilaisia tekniikoita, joilla valokuvien aitoutta voidaan arvioida. Tarkastelen t\u00e4ss\u00e4 tutkielmassa niin sanottuja passiivisia tekniikoita, jotka eiv\u00e4t edellyt\u00e4 kuvasta mink\u00e4\u00e4nlaista ennakkotietoa, kuten vesileimaa. Vertailen viitt\u00e4 t\u00e4llaista tekniikkaa laatimani nelj\u00e4 kohtaa k\u00e4sitt\u00e4v\u00e4n kriteerist\u00f6n pohjalta. Vertailtavia ominaisuuksia ovat tarkkuus, tunnistetut muokkaustyypit, rajoitukset sek\u00e4 vakaus vastatoimia vastaan. Vertailu osoittaa, ett\u00e4 er\u00e4s merkitt\u00e4vimmist\u00e4 tekniikoiden ongelmista on niiden huono toleranssi kuvan h\u00e4vi\u00f6llisen pakkaamisen suhteen. Koska h\u00e4vi\u00f6llisist\u00e4 tallennusmuodoista k\u00e4ytetyin on JPEG, olen toteuttanut nelj\u00e4 valokuvien aitouden arviointimenetelm\u00e4\u00e4, jotka hy\u00f6dynt\u00e4v\u00e4t JPEG-pakkauksen ominaispiirteit\u00e4. Kolme tekniikoista on l\u00e4hes sellaisenaan esitelty aiemmin alan kirjallisuudessa. Nelj\u00e4s on oma muunnelmani yhdest\u00e4 edell\u00e4 mainituista. Kaksi menetelmist\u00e4 hy\u00f6dynt\u00e4\u00e4 JPEG-pakkauksen ytimeen kuuluvia diskreetti\u00e4 kosinimuunnosta ja kvantisointia. Toiset kaksi puolestaan tarkastelevat JPEG-pakkauksen aiheuttamaa kuvan laatikoitumista. Tutkielman tarkoituksena on selvitt\u00e4\u00e4, ovatko useamman tekniikan avulla saavutettavat tulokset oleellisesti luotettavampia, kuin yksitt\u00e4isell\u00e4 menetelm\u00e4ll\u00e4 saavutettavat. Esit\u00e4n my\u00f6s testitulokset, jotka olen saanut testaamalla tekniikoita laatimani kuva-aineiston suhteen. Testitulosten perusteella voidaan todeta, ett\u00e4 useamman tekniikan avulla kuvan aitoudesta saadaan kokonaisvaltaisempi kuva, ja hieman useampia tilanteita saadaan todella katettua. Joiltain osin tarkasteltujen tekniikoiden toimintaedellytykset poikkeavat toisistaan, mutta kaikkien tekniikoiden kanssa t\u00f6rm\u00e4t\u00e4\u00e4n kuitenkin lopulta samaan rajoitukseen. Merkitt\u00e4vin tekij\u00e4 kuvav\u00e4\u00e4renn\u00f6sten onnistuneen tunnistamisen kannalta n\u00e4ytt\u00e4isi olevan ennen ja j\u00e4lkeen kuvan muokkaamisen k\u00e4ytetyt pakkauslaadut. Onnistunut tunnistaminen edellytt\u00e4\u00e4, ett\u00e4 muokkaamisen j\u00e4lkeinen laatu on ainakin jonkin verran muokkaamista edelt\u00e4v\u00e4\u00e4 laatua korkeampi. M\u00e4\u00e4ritelt\u00e4ess\u00e4 JPEG-pakkauksen laatu asteikolla 1-100, n\u00e4ytt\u00e4isi 1-20 yksik\u00f6n ero riitt\u00e4v\u00e4n. Vaadittava ero on pienin pakkauslaadun korkeimmilla tasoilla. Muita vaikuttavia tekij\u00f6it\u00e4 ovat muokkauksen tyyppi, kuvan sis\u00e4lt\u00f6 sek\u00e4 muokatun alueen koko.", "language": "", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted using Plone Publishing form by Ilkka Ollari (iltaolla) on 2010-08-27 05:54:42.332475. Form: Pro gradu -lomake (1 tekij\u00e4) (https://kirjasto.jyu.fi/julkaisut/julkaisulomakkeet/pro-gradu-lomake-1-tekijae). JyX data:", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted by jyx lomake-julkaisija (jyx-julkaisija@noreply.fi) on 2010-08-27T05:54:44Z\nNo. of bitstreams: 2\nURN:NBN:fi:jyu-201008272497.pdf: 2974939 bytes, checksum: 98334e9997f30c63411c3f876330a2e3 (MD5)\nlicense.html: 5008 bytes, checksum: 4a52868fd886e500bb0d357440f63346 (MD5)", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Made available in DSpace on 2010-08-27T05:54:44Z (GMT). No. of bitstreams: 2\nURN:NBN:fi:jyu-201008272497.pdf: 2974939 bytes, checksum: 98334e9997f30c63411c3f876330a2e3 (MD5)\nlicense.html: 5008 bytes, checksum: 4a52868fd886e500bb0d357440f63346 (MD5)\n Previous issue date: 2010", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.format.extent", "value": "100 sivua", "language": null, "element": "format", "qualifier": "extent", "schema": "dc"}, {"key": "dc.format.mimetype", "value": "application/pdf", "language": null, "element": "format", "qualifier": "mimetype", "schema": "dc"}, {"key": "dc.language.iso", "value": "fin", "language": null, "element": "language", "qualifier": "iso", "schema": "dc"}, {"key": "dc.rights", "value": "In Copyright", "language": "en", "element": "rights", "qualifier": null, "schema": "dc"}, {"key": "dc.subject.other", "value": "digital image forensics", "language": null, "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.subject.other", "value": "JPEG", "language": null, "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.title", "value": "Digitaalisten kuvav\u00e4\u00e4renn\u00f6sten tunnistaminen JPEG-pakkausta hy\u00f6dynt\u00e4en", "language": null, "element": "title", "qualifier": null, "schema": "dc"}, {"key": "dc.type", "value": "master thesis", "language": null, "element": "type", "qualifier": null, "schema": "dc"}, {"key": "dc.identifier.urn", "value": "URN:NBN:fi:jyu-201008272497", "language": null, "element": "identifier", "qualifier": "urn", "schema": "dc"}, {"key": "dc.type.dcmitype", "value": "Text", "language": "en", "element": "type", "qualifier": "dcmitype", "schema": "dc"}, {"key": "dc.type.ontasot", "value": "Pro gradu -tutkielma", "language": "fi", "element": "type", "qualifier": "ontasot", "schema": "dc"}, {"key": "dc.type.ontasot", "value": "Master\u2019s thesis", "language": "en", "element": "type", "qualifier": "ontasot", "schema": "dc"}, {"key": "dc.contributor.faculty", "value": "Informaatioteknologian tiedekunta", "language": "fi", "element": "contributor", "qualifier": "faculty", "schema": "dc"}, {"key": "dc.contributor.faculty", "value": "Faculty of Information Technology", "language": "en", "element": "contributor", "qualifier": "faculty", "schema": "dc"}, {"key": "dc.contributor.department", "value": "Tietojenk\u00e4sittelytieteiden laitos", "language": "fi", "element": "contributor", "qualifier": "department", "schema": "dc"}, {"key": "dc.contributor.department", "value": "Department of Computer Science and Information Systems", "language": "en", "element": "contributor", "qualifier": "department", "schema": "dc"}, {"key": "dc.contributor.organization", "value": "University of Jyv\u00e4skyl\u00e4", "language": "en", "element": "contributor", "qualifier": "organization", "schema": "dc"}, {"key": "dc.contributor.organization", "value": "Jyv\u00e4skyl\u00e4n yliopisto", "language": "fi", "element": "contributor", "qualifier": "organization", "schema": "dc"}, {"key": "dc.subject.discipline", "value": "Tietojenk\u00e4sittelytiede", "language": "fi", "element": "subject", "qualifier": "discipline", "schema": "dc"}, {"key": "dc.type.coar", "value": "http://purl.org/coar/resource_type/c_bdcc", "language": null, "element": "type", "qualifier": "coar", "schema": "dc"}, {"key": "dc.rights.accesslevel", "value": "openAccess", "language": "fi", "element": "rights", "qualifier": "accesslevel", "schema": "dc"}, {"key": "dc.type.publication", "value": "masterThesis", "language": null, "element": "type", "qualifier": "publication", "schema": "dc"}, {"key": "dc.subject.oppiainekoodi", "value": "601", "language": null, "element": "subject", "qualifier": "oppiainekoodi", "schema": "dc"}, {"key": "dc.subject.yso", "value": "kuvat", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "digitaalikuvaus", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "kuvank\u00e4sittely", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "v\u00e4\u00e4renn\u00f6kset", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "todentaminen", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.format.content", "value": "fulltext", "language": null, "element": "format", "qualifier": "content", "schema": "dc"}, {"key": "dc.rights.url", "value": "https://rightsstatements.org/page/InC/1.0/", "language": null, "element": "rights", "qualifier": "url", "schema": "dc"}, {"key": "dc.type.okm", "value": "G2", "language": null, "element": "type", "qualifier": "okm", "schema": "dc"}]
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