Cire bayanan meta na EXIF daga hotuna _

Yadda cire EXIF ke aiki

Fayil ɗin JPEG jerin sassan da aka sa alamar ake kira APP markers ne, suna farawa daidai bayan sa hannu na byte biyu na SOI (0xFFD8). Bayanan EXIF suna zaune a APP1, GPS yana zaune a cikin block ɗaya na APP1 a matsayin sub-IFD, da IPTC yana zaune a APP13. Mai cire bayanan yana tafiya kowane marker, yana gano waɗanda ke ɗaukar bayanan meta, yana cire su, kuma yana sake haɗa abin da ya rage ya zama JPEG mai inganci.

1. Bincike APP markers. Kayan aikin yana karanta ArrayBuffer mai tsatsa kuma yana tafiya jerin marker na JFIF byte biye da byte. Kowane marker tag na byte biyu yana gano nau'in sashi: APP0 (taken JFIF), APP1 (EXIF da XMP), APP13 (Photoshop da IPTC), da sauransu ta APP15. Mai binciken yana rikodin offset da tsawo na byte na kowane sashi a cikin ƙaramin tebur kafin taɓa kome, don buffer na asali ya kasance cikakke a cikin ƙwaƙwalwa.
2. Buɗe ɓoye tags na EXIF. Abin da ke cikin APP1 ƙaramin tsari na TIFF ne tare da Directories guda huɗu na Fayil Hoto: 0th IFD (sifofin hoton babban), Exif SubIFD (buɗaɗɗe, ruwan tabarau, tsayin hotuna, ISO), GPS IFD (latitude, longitude, tsawo, alkibla), da 1st IFD (hoto ƙarami da aka saka). Kowane tag yana ɗaukar lambar numeric, nau'in bayanai (byte, gajere, mai tsawo, rabo, string na ASCII), da ƙima. Kayan aikin yana auna lambobin numeric zuwa sunaye masu iya karantawa ta ɗan adam ta amfani da kamus na tag na piexifjs, sannan yana nuna su a panel na bayanan meta da aka ƙungiya ta IFD.
3. Nuna tags na GPS a haskaka. Ana haskaka kowane tag a cikin GPS IFD da badge na sirri ja. Ana ajiye latitude da longitude a matsayin lambobi uku na rabo (digiri, mintoci, dakiku) da kuma alkiblar tunani (N ko S, E ko W). Kayan aikin yana juyar da su zuwa digiri decimal na sa hannu tare da digits shida na daidaito (~11 cm a equator) kuma yana nuna sakamakon a cikin panel na GPS tare da haɗin OpenStreetMap. Babu buƙatar tile da ke fita — haɗin ana ƙira shi gida kawai kuma yana buɗewa idan kuka danna shi kawai.
4. Cire bayanan meta. Don fayilolin JPEG hanyar tsoho tana amfani da piexifjs don cire sashi na APP1 gaba ɗaya, dawo da dataURL sabon tare da bayanan pixel ba tare da taɓa ba. Lokacin da 'Kiyaye matsayi' ya kunna, kayan aikin yana juyar da hoto a <canvas> don daidaita da ƙimar tag na asali na Orientation (1–8) kafin cire, don sakamakon mai ganuwa ya daidaita da abin da kyamarar ka ta yi niyya — ana ɗab da juyawa a cikin pixels maimakon dogaro da tutar bayanan meta.
5. Hanyar sake-ɓoyewa ta canvas. Lokacin da 'Kiyaye profile na launi na ICC' ya kashe, kayan aikin yana zana hoto zuwa <canvas> da aka ɓoye kuma yana kira canvas.toBlob('image/jpeg', quality). Wannan hanyar tana cire duk abin (EXIF, XMP, IPTC, profile na launi na ICC, hoto ƙarami) kuma yana ba ku damar sarrafa slider na ingancin JPEG daga 60 zuwa 100. Tsoho shine 92, wanda ke samar da fayiloli a cikin ƴan kashi na girman asali a ingancin da ba za a iya bambanta ba da tushen akan yawancin hotuna.
6. Sauke fayil ɗin tsabta. Ana ba da blob da aka tsabtace a matsayin sauke mai suna <original-name>-stripped.jpg. Kayan aikin yana sake-bincike sakamakon kuma yana tabbatar da sashi na GPS na EXIF bazu kafin haɗin sauke ya bayyana, don ba za ku taɓa samun fayil da aka sa masa suna 'stripped' da ya har yanzu yana ɗaukar tag na wurin ba. Fayilolin PNG da WebP ba sa ɗaukar EXIF tun da farko; kayan aikin yana nuna saƙon 'Babu EXIF' kuma yana tsallake matakin cire don waɗancan tsaruka.

Me ya sa a cire EXIF kafin raba

• Sirrin wurin. Kwallayen hoto suna saka kididdigar GPS daidai a kowane hoto ta tsoho. JPEG daga gidan abinci, ofis, ko gida yana ɗaukar wannan adreshin a cikin bayanan meta da shi a daidaito kusan mita biyar. Cire tag na GPS kafin aikawa zuwa kafofin watsa labarai na zamantakewa, imel baƙo, ko haɗa allon zuwa tikitin goyon baya na jama'a kuma ku cire wannan alamar wurin gaba ɗaya.
• Ɓoye sunan mai a cikin bugawa. Ɗan jarida, masu fafutuka, da masu bayyana asiri suna cire EXIF kafin gabatar da hotuna saboda lambar jerin kamera, sigar firmware na ruwan tabarau, da lokacin ƙirƙirar duka za a iya kwatanta su da sauran hotuna da aka buga don gano mai hoto. Cire waɗancan tags matakin tsaro na aiki ne na asali don kowa wanda sunansa ba ya kamata ya haɗa da na'ura takamaiman ta jiki.
• Girman fayil ƙarami. Kwallan hoto na JPEG yau da kullun yana ɗaukar KB 5 zuwa 15 na bayanan meta a cikin sashi na APP1 ɗinsa, ciki har da hoto ƙarami da aka saka na 160 × 120. Wannan ƙarami ne idan aka kwata da hoto na MB 5, amma cire shi a cikin jerin hotuna 1,000 yana adana MB 5 zuwa 15 a kowace zagayowar loda — yana da amfani lokacin da kuke yanke katalogin kayan aiki, ɗakin adanawa na hoto, ko fitar da Pinterest.
• Cire alamar kamera. Yin kamera, ƙirar, sigar firmware, mai gano ruwan tabarau, da yawan aiki na shutter suna samar da alamar da za ta iya haɗa hotuna a cikin lodawa daban-daban har ma lokacin da EXIF in ba haka ba ba ya da muhimmanci. Idan kuna raba hotuna ba tare da bayyana kayan aikin ku ba (rahoton kuskure, gabatarwa na gasa, portfolio na ɓoye sunan mai), Exif SubIFD shine inda wannan bayanan mai gano yana zaune. Cire shi kuma an karya haɗin.

Amfani na yau da kullun

Cire EXIF yana bayyana ko'ina hoto ya canja hannaye kuma bayanan meta da ke ɗauka na iya haifar da matsaloli ga mai aika ko batun.

• Lodawa zuwa kafofin watsa labarai na zamantakewa: yawancin dandali suna cire EXIF ta gefen uwar garken ta kowane hali, amma cire ta gefen abokin ciniki da farko yana nufin kididdigar asali ba a taɓa watsa su zuwa uwar garken dandali ba kwata-kwata. Idan layin aiki ɗinsu ya taɓa malala (ko a yi musu sammaci), GPS na asali ba a cikin rikodin ɗinsu saboda ba a aika shi ba.
• Jarida da hoto na takardu: sabis na waya da tebur na hoto suna buƙatar bayanan meta tsabta don yin alaƙa da sunaye da bayanan taken ana sarrafa su ta tebur, ba kamera ba. Editocin hoto a AP, Reuters, da AFP duka suna gudanar da hotuna masu shigowa ta matakin tsabtace bayanan meta kafin su buga.
• Lissafin dukiya da kayan aiki: wakilan gidaje da masu siyarwa na e-commerce galibi suna loda hotuna da aka ɗauka a adreshin dukiyar ko gidan ajiye kaya. Cire GPS kafin loda yana hana lissafin daga buga adreshin kasuwanci daidai a fayil ba da gangan ba — yana da amfani lokacin da gidan ajiya gida ne masu zaman kansu ko dukiyar har yanzu ana zaune a ciki.

Misali da aka yi aiki

JPEG na MB 3.5 da aka ɗauka akan iPhone na kwanan nan yana ɗaukar kusan KB 12 na bayanan meta na APP1: kididdigar GPS tare da alkibla da tsawo, lokacin ɗaukar hoto har zuwa millisecond, ƙirar kamera da mai gano ruwan tabarau, saituna na fari-daidai, da hoto ƙarami da aka saka na 160 × 120. Bayan cire tare da hanyar piexif ta tsoho, fayil ɗin ya sauka a MB 3.488. Hakan yana da KB 12 ƙarami, pixels ɗaya da na asali, kuma ba tare da ping na wurin ba. Panel na GPS a sama zai nuna daidai wane kididdigar aka cire kafin ku sauke.

Mene ne bayanan meta na EXIF?

EXIF (Exchangeable Image File Format) ma'auni ne da ke bayyana yadda kyamarori na dijital da kwallayen hoto ke ajiye bayanan meta a cikin fayilolin hoto. Kwallan hoto na JPEG yau da kullun yana ɗaukar yin kamera da ƙirar, tsayin hotuna na ruwan tabarau, gurin ɗaukan hoto, ISO, wurin GPS daidai (har zuwa ƴan mita), lokacin ƙirƙirar, da hoto ƙarami da aka saka — duka marasa ganuwa a cikin hoton da aka nuna kansa amma masu iya karanta ta kowane aikace-aikace mai sani da EXIF, ciki har da mai binciken fayil na OS da yawancin kayan aikin gyara hoto.

Me ya sa kamata na cire EXIF kafin raba hoto?

Tag na GPS yana bayyana inda aka ɗauki hoto, har zuwa ƴan mita. Raba hoto ba tare da cire shi ba kuma kana raba wannan wurin da kowa da ya karɓi fayil ɗin. Lambobin jerin kamera da masu gano ruwan tabarau kuma na iya yin alamar mai hoto a cikin lodawa daban-daban, wanda ke da mahimmanci ga kowa mai buga a ɓoye sunan mai. Cire yana cire duk wannan kafin fayil ɗin ya barin na'urarku.

Shin wannan yana shafar ingancin hoto?

Hanyar piexif ta tsoho tana cire sashi na APP1 ba tare da taɓa pixels na hoto ba, don ingancin ya zama bits ɗaya da na asali. Hanyar sake-ɓoyewa ta canvas (ana amfani da ita lokacin da 'Kiyaye profile na launi na ICC' ya kashe, ko lokacin da 'Kiyaye matsayi' ya kunna don hoto da aka juyar) yana sake-ɓoye pixels a ƙimar slider na ingancin JPEG da aka zaɓa — saita slider zuwa 95 ko sama da haka don ajiye sakamakon mai ganuwa kusa da tushe akan yawancin hotuna.

Fa game da fayilolin HEIC daga iPhones?

Cire HEIC ya dogara da goyan bayan HEIC na asali na mai binciken ka. Safari 13+ yana buɗe ɓoye HEIC ta asali; Chrome da Firefox ba sa. Idan mai binciken ka ba ya iya nuna HEIC, yi amfani da zaɓin 'Fitar a matsayin JPEG' na wayar ka da farko (a cikin iOS Photos: Raba → Zaɓuɓɓuka → Mafi Dacewa), sannan loda JPEG anan. Matakin cire akan fayil ɗin da aka juyar yana aiki iri ɗaya da JPEG kowa.

Kowane cire yana gudana gida a cikin mai binciken ka. Hoton asali ba ya taɓa isa uwar garken kuma ana samar da fayil ɗin da aka tsabtace gaba ɗaya daga ArrayBuffer da aka loda zuwa ƙwaƙwalwa a lokacin loda. Saka hoto a sama, duba bayanan meta, da sauke kwafin da aka cire.