JPEG . RGB YUV, . Y , U V - . RGB YUV :
RGB -> YUV:
Y = 0.299*red + 0.587*green + 0.114*blue
U = -0.147*Red - 0.289*green + 0.436*blue ~(BLUE-Y)/2
V = 0.615*red - 0.515*green - 0.100*blue; ~(Red -y)
YUV -> RGB:
Red = Y + 1.140*v
Green = Y - 0.396*u - 0.581*v
Blue = Y + 2.029*u.
' .
, . . JPEG "" . Y , U V, , , .
. . . , , , ', , .
(), . 88 ( 64 ). , , 88 . 64 64 , "" . , , . . , , . ' .
, , , . , , , . , , . - .
|
|
|
. , . . . ³ , .
- , . , , , , . . , , :
1- 2 6- 7 15-16
/ / / / /
3 5 8 14...
|/ / /
4 9 13
/ /
10 12
|/
. JPEG ' .
JPEG
. , , , . , , PCX. , , - 256- , . , " ".
. "
" . , , . - ( tag - ). . " " . - - '. , , , , , , . ͳ
.
JPEG. . JPEG , - "FF", . "C0" .
SOI ("Start Of Image" - ) "FF D8", EOI ("End Of Image" - ʳ ) - "FF D9". , , . :
|
|
|
<FF> <> < (2 )> < (-2 )>.
³ 2 , ( ). :
1)
2) , .
, - , .
' , JPEG "", '. ' JPEG , . , JPEG .
JPEG
, JPEG SOI. , . , .
App0, : App0-jfif, App0-jfxx, App0, .
, : , , , . , , , . - . , . - FTP JPEG, JPEG, , .
App0-jfif
' . ³ "FF E0", . 16 , . , .
' App0-jfif - "JFIF" (4a 46 49 46 00). : "JPEG File Interchange Format" - JPEG. JPEG . "" , - .
, JFIF. () , (), - , . , , "01 02" 1.2.
ϳ App0-jfif , .
App0-jfxx
, , App0-jfif. ³ . App0 ("FF E0"), , . ' , , "JFXX" (4a 46 58 58 00). , THUMBNAIL (" "), . Thumbnail jpeg' 256- Truecolor' .
App0
³ App0-jfif App0-jfxx App0. , , . , "JFIF" "JFXX". "", "", "" "0" , "80". , , , .
|
|
|
- , .
JPEG, App0. .
SOF
. , . SOF - "Start of Frame" ( ). SOF C0 CF.
SOF :
1) (1 ) - 8, 12 16;
2) (2 ) ( - );
3) (2 );
4) (1 ) - 3 1 ;
5) ( 3 ). - . - ( ) ( ). - .
SOS
, SOS ("Start of Scan" - ), - "FF DA". . ³ - , EOI (End Of Image) - "FF D9".
.
(x,yi), ᒺ. , , x,yi x+1, yi+1 ᒺ. . . , . . ǒ , . , , . . .
