1
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>> [Daqq tal-mużika]

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>> ZAMYLA Chan: blow Ejja
affarijiet up ma 'resize.

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Fil resize, l-utent se jgħaddu, permezz
kmand tal-linja, immaġni Bitmap li

4
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huma jridu li inti iskala minn numru
li huma wkoll tgħaddi fi,

5
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fil-linja tal-kmand.

6
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Kif nistgħu nagħmlu dan?

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>> Ukoll, L-ewwelnett, ejja
din tinqasam passi.

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Int ser tixtieq li tiftaħ il-infile
li huma jagħtuk, kif ukoll

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joħolqu u tiftaħ il-outfile li
int ser tpoġġi l-

10
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image daqs ieħor pulzieri

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Imbagħad, għax int ristrutturazzjoni, u
għaliex dan huwa Bitmap, din header, hekk

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int ser taġġorna wkoll il-header
informazzjoni għall-outfile,

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u jiktbu dak pulzieri

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Imbagħad, int ser jinqara fil-
l scanline tal-infile,

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pixel--pixel minn, resizing orizzontalment
u l-kitba dawk pixels fil-

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outfile, kif speċifikat
mill-iskala l-utent.

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>> Int ser tiftakar li
żid padding kif meħtieġ.

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Aktar dwar dan aktar tard.

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U mbagħad, ukoll resize vertikalment.

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OK.

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Allura dan se jkun ftit aktar
ikkumplikat minn Who Magħmul Huwa, iżda

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dak li huwa simili hija li copy.c se,
għal darb'oħra, jkunu utli ħafna.

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Ftakar li copy.c jiftaħ fajl,
jaġġorna l-informazzjoni header għall-

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outfile, allura jaqra fil-scanline,
pixel-'pixel mill-kitba kull pixel

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fil scanline-fajl output tal.

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>> Għalhekk għal darb'oħra, l-ewwel pass tiegħek jista 'probabbilment
jkun li cp, copy.c, resize.c

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fis direttorju PSET5 tiegħek.

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Ftakar għalkemm, qabel ma jibagħtu kopja tagħha,
biex taċċerta ruħek li tifhem

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copy.c sewwa ħafna.

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OK.

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>> Mela ejja jiftaħ fajl.

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Inti taf kif għandek tagħmel dan.

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Jien ser leave li lilek.

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Sussegwentement, jaġġornaw l-informazzjoni header
għall-outfile.

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Għaliex għandna Bitmap ġdid,
għandna info header ġdid.

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X'hemm jinbidlu hawn?

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Ukoll, id-daqs fajl huwa se jibdlu
għaliex aħna qed tmur li jkollhom aktar

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pixels minn qabel.

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Id-daqs immaġini huwa, għalhekk, ukoll
se jibdlu, kif inhu l-

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wisa 'u l-għoli.

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>> Allura għalih il-varjabbli huma dawk, eżattament?

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Ukoll, jekk inti tħares lejn il-header
informazzjoni, tara hemm

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biSizeImage, li jirrappreżenta t-total
daqs tal-immaġini fil bytes,

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inklużi pixels u padding.

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biWidth huwa l-wisa 'l-immaġini
pixels, nieqes l-padding.

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biHeight huwa l-għoli ta '
l-immaġini fil pixels.

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U hekk dawk jinsabu fil-
structs BITMAPFILEHEADER u

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BITMAPINFOHEADER.

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Tista 'tgħid liema waħda hija li minn
ser bmp.h u tħares lejn l-

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Struct BITMAPINFOHEADER u jaraw
għalih il-varjabbli huma elenkati hemmhekk.

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>> Allura biex taġġorna l-header outfiles
informazzjoni, int ser jridu

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tibdel dawk il-valuri tal-
għoli u l-wisa.

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Iżda ċansijiet huma, inti jista 'jkollok bżonn xi
ta 'informazzjoni header tal-infile tal

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aktar tard, hekk aħjar li jżommu rekord tat-tnejn.

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Iżda tkun ċara ħafna ma 'varjabbli tiegħek
ismijiet hekk li inti ma aċċidentalment

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ikteb il-valuri skorretti fir
l-header għall-outfile.

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>> Allura issa ejja nikseb qari fis
l-pixel-by pixel scanline.

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Għal darb'oħra, aħna qed tmur li jduru għal trusty tagħna
fajl I / O librerija, u ħarsa lejn

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il-funzjoni fread.

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fread jieħu fil pointer għal Istituzzjonjijiet
li se jkun fiha l-bytes li

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int qari, id-daqs ta 'kull
element li qed taqra -

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għal darb'oħra, sizeof se tkun utli
jiffunzjonaw hawn, in-numru tal-

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elementi ta 'daqs, id-daqs, li int
qari, u mbagħad finalment, il-

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inpointer, il-fajl li
int qari minn.

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Allura inti qed tieħu elementi numru
ta 'daqs minn inpointer, u

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tqegħid tagħhom fiċ-data.

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>> Issa wasal iż-żmien biex resize orizzontalment.

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jekk n ugwali 2, allura għal kull pixel fil-
l infile, aħna qed tmur biex tiktibha

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darbtejn fil-outfile.

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Kif nistgħu jiktbu fajls?

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Well, aħna għandna l-funzjoni fwrite, hekk
aħna ħadt l-pointer għall-Istituzzjonjijiet

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li fiha l-bytes li int
miktub minn, u allura aħna jgħaddu

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daqs, in-numru, u l-output, fejn
int ser tkun bil-miktub dan.

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U mbagħad jirrepeti proċess, se jkun
kapaċi a iterattiv sempliċi għall-loop.

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>> Iżda għandna bżonn biex tiftakar
żid padding pulzieri

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00:04:21,740 --> 00:04:26,040
Il-kunċett ta 'padding hija li, ukoll,
kull pixel huwa tliet bites, iżda l-

77
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daqs ta 'kull must scanline
ikun multiplu ta '4 bytes.

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Allura jekk in-numru ta 'pixels mhuwiex
multiplu ta '4, għandna bżonn li żżid xi

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ikkuttunar, li huwa biss zeroes.

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Issa, b'differenza Who Magħmul Huwa, u b'differenza
kopja, imbagħad immaġni infile u l-

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fajl outfile jkunu jkollhom differenti
ikkuttunar differenti għaliex qed

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b'wisa 'differenti.

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>> OK.

84
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Allura forsi formula kieku
jaqgħu fil handy hawn.

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I ser tħalli f'idejn għalik li ssib it out, iżda
jgħidlek li, jiktbu ikkuttunar,

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ukoll, huwa biss funzjoni fputc sempliċi,
tgħaddi fil-karattru

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li inti tixtieq li tikteb, u mbagħad
il-pointer fajl li inti

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tixtieq li tikteb.

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Allura issa li konna daqs ieħor orizzontalment,
u imbagħad jintuża padding,

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ftakar li għandek bżonn biex jimxu fajl tiegħek
indikatur tal-pożizzjoni, għaliex inti

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ma tistax fread fis padding.

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Allura inti tixtieq li tagħmel ċert li l-fajl tiegħek
indikatur tal-pożizzjoni fil-infile

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hija fil-punt korretta.

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Għaliex aħna rridu wkoll li
resize vertikalment.

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Ma nistgħux sempliċement stretch orizzontalment,
għaliex kull bżonnijiet ringiela

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li jiġu kkupjati n darbiet.

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>> Issa, hemm diversi differenti
modi biex tagħmel dan.

98
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Allura wieħed, nistgħu nużaw metodu jikteb, fl
li aħna niftakru kollha tal-pixels

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ta 'ringiela mogħtija fil-firxa, u
allura aħna tikteb li array bħala

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ħafna drabi kif meħtieġ.

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Jew hemm il-metodu recopy fejn,
wara l-qari f'ringiela waħda l infile

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u mbagħad bil-miktub li fil-outfile,
żżid l-ikkuttunar, aħna fseek

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lura għall-bidu tal-filliera oriġinali,
u mbagħad irrepeti l-orizzontali

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resizing minn hemm.

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Irrispettivament mill-metodu, għalkemm, inti ser
tixtieq kull pixel li jiġu ripetuti

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n darbiet, u kull ringiela li jkun
n darbiet ripetut kif ukoll.

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>> Ma 'dan, inti ser ikollok Bitmap
akbar minn ħajja.

108
00:06:09,160 --> 00:06:11,760
Jisimni Zamyla, u dan huwa CS50.

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