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>> [Daqq tal-mużika]

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>> ROB Bowden: Hi, jien Rob, ejja
tipprova dan fuq għad-daqs.

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Allura, aħna darb'oħra ser tibda bil-
bażikament kopja tal-copy.c, u

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jagħmlu ftit tibdiliet.

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Nota immedjatament naraw bidla, fejn
minflok verifika biex tara jekk

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argc ma ugwali 3, irridu li jiċċekkjaw
jekk argc ma ugwali 4, peress li

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issa aħna mhux biss tieħu fi infile
u outfile, imma aħna wkoll qed tieħu fl

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n, li huwa l-ammont li aħna qed
skalar l-immaġini oriġinali mill-.

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Ladarba aħna żgur ta 'dak, nistgħu biss
jikkonvertu n għal integer użu atoi.

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>> Allura, issa aħna qed tmur biex joħolqu xi
psewdonimi, biss sejħa ARGV 2 infile, u

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ARGV 3 outfile, minħabba ARGV 2 u
ARGV 3 mhumiex ismijiet utli ħafna.

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Issa rridu li jivverifika sabiex ikun żgur n hija
fil-limiti nistennew, sabiex il-

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spec jispeċifika li jekk huwa inqas minn jew
żero, jew aktar minn 100,

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allura dak l-fattur resize invalidu,
u għandna twissi lill-utent ta 'dak.

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>> Ladarba aħna qed hinn dak kollu li, nistgħu
finalment tiftaħ infile tagħna, u għandna bżonn

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għal żball jivverifika sabiex ikun żgur li l-
ftuħ ma naqasx milli għal xi raġuni.

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Għandna bżonn ukoll li tiftaħ outfile tagħna, u
darb'oħra żball jivverifika sabiex ikun żgur li

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ma naqasx milli għal xi raġuni.

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Imma kun żgur jekk il-ftuħ tal-
outfile naqset li għandna bżonn li tagħlaq

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l infile, li kien diġà miftuħa.

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>> Għalhekk, jekk wieħed jassumi li ma ifallu,
we're - hekk kif fil copy.c--

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ser jinqara fil-header
mill-infile.

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Aħna qed tmur biex tagħmel ċert li huwa validu
Bitmap, iżda issa aħna qed tmur biex tagħmel xi

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affarijiet daqsxejn differenti.

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Allura l-ewwel, aħna qed tmur jridu
tiftakar il-wisa 'oriġinali' u għoli

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tal-infile, għaliex aħna qed tmur biex
jinbidlu lilha għall-outfile.

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Allura issa ftakar li għal raġunijiet stramba
bi.biheight, huwa negattiv, u

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sabiex l-għoli attwali, b'mod pożittiv, aħna
jridu jieħdu l-valur assolut.

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>> Issa, l-ikkuttunar se tkun l-istess
kalkolu kif kienet fil copy.c,

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jużaw il-wisa qodma, u issa aħna qed
attwalment se jibdlu

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X'hemm fil-header tagħna.

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Allura aħna qed tmur biex jimmultiplikaw wisa tagħna billi
n, peress li aħna qed skalar il-wisa billi

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n, immoltiplika l-għoli mill-n, peress li aħna qed
skalar minn n, u issa għandna

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il-kalkolu ta 'padding ġdida
ibbażata fuq il-wisa ġdid.

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>> Allura issa għandna bżonn li jibdel uħud
oqsma oħra fil header tagħna.

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Bi.biSizeImage suppost tkun il-
daqs tal-bytes kollha fil-pixels

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u padding ta 'l-immaġini.

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U għalhekk l-daqs ta 'ringiela waħda ta' tagħna
immaġini huwa daqs tal RGB triplu, id-daqs

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ta 'pixel wieħed, darbiet in-numru
pixels fir-ringiela, kif ukoll il-ikkuttunar fuq

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l-aħħar tal-filliera.

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U allura aħna qed tmur biex timmultiplika din minn
valur assolut ta 'għoli tagħna sabiex inġibu

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in-numru totali ta 'bytes
fid-data immaġini.

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bf.bfSize huwa biss in-numru totali
ta 'bytes fir image data tagħna, sabiex

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bi.biSizeImage, flimkien mal-
daqs tal headers tagħna.

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Għalhekk, billi żżid fuq id-daqs tal-fajl Bitmap
header, u d-daqs ta 'info Bitmap

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header, OK.

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Hekk li kollox għandna bżonn li
bidla fl headers tagħna.

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Issa aħna ser jiktbu l-header tal-fajl Bitmap
li outfile tagħna, u info Bitmap tagħna

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header għall outfile tagħna, u issa
aħna lesti biex tibda tmur

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matul l-pixels attwali.

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>> Hekk irridu jtenni fuq
scan linji tal-infile'S.

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Allura aħna tixtieq li jtenni fuq oldheight.

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Dan huwa għaliex għandna bżonn li tiftakar il-
għoli oriġinali, qabel we jibdlu

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u mqassma lilha mill n.

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Issa aħna qed tmur biex jaqra waħda
ringiela tat-infile fi

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buffer ta 'daqs oldwidth.

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Allura hawn, aħna qed freading daqs tal RGB
tripla, pixel wieħed, u l-wisa antika ta '

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minnhom mill-infile fis buffer tagħna.

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U li għaddej biex tkun sħiħa
ringiela f'dan il firxa.

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Allura issa, irridu li jtenni n darbiet biex
Stampa din il-filliera li outfile tagħna n darbiet.

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U hekk dan huwa dak li dan loop qed tagħmel.

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Dan loop ġewwa huwa mtennija fuq l-
ringiela innifsu, fuq il-firxa, l-istampar

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kull pixel fil-firxa n darbiet.

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Allura l-element 0 qiegħed jiġi stampat
n drabi, l-ewwel element qed

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stampati n darbiet.

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U thats it-tip ta 'kif aħna qed tmur biex
orizzontalment skala kbira fil-outfile, u

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dan loop, peress li aħna qed looping n
drabi, huwa kif aħna qed tmur biex

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iskala vertikalment.

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>> Down hawn, naraw li għandna bżonn li jiżdiedu
l-ikkuttunar fl-aħħar ta 'kull ringiela.

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C'est pourquoi dan huwa ġewwa l-għar loop
thats istampar u l-ringieli n ta 'ftit

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dan filliera waħda mill-infile.

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Imbagħad stabbiliti hawn, jien ser skip fuq
l-ikkuttunar fil-infile, peress li ladarba

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aħna qed isir ma 'ringiela waħda mill-
infile, aħna ma jimpurtahom dwar

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dak l-ikkuttunar kien.

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Aħna biss trid li tikseb l-tieni ringiela.

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U allura aħna ser loop lura u jagħmlu dak kollu
dan jerġa għat-tieni ringiela.

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>> Fl-aħħarnett, ladarba aħna qed isir b'dak kollu li,
nistgħu tagħlaq il infile, qrib

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l outfile, u r-ritorn
0 għaliex aħna qed isir.

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>> Jisimni Rob, u dan kien resize.

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>> [Daqq tal-mużika]