function?jpeg
%?This?is?a?JPEG?encoding?&?decoding?program?of?still?image.
%?it?does?not?use?level?shifting.
%?Discrete?Cosine?transform?（DCT）?is?performed?both?by?classical?&?Chen‘s
%?Flowgraph?methods.?Predefined?JPEG?quantization?array?&?Zigzag?order?are
%?used?here.?‘RUN‘?‘LEVEL‘?coding?is?used?instead?of??Huffman?coding.
%?Compression?ratio?is?compared?for?each?DCT?method.?Effect?of?coarse?and?fine?quantization?is
%?also?examined.?The?execution?time?of?2?DCT?methods?is?also?checked.
%?In?addition?most?energatic?DCT?coefficients?are?also?applied?to?examine
%?the?effect?in?MatLab?7.4.0?R2007a.?Input?is?9?gray?scale?pictures?&
%?output?is?9*9=81?pictures?to?compare.?Blocking?effect?is?obvious.
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????%--------------------------?Initialization?-----------------------------
????%?JPEG?default?quantization?array
????Q_8x8?=uint8（[
????????????16?11?10?16??24??40??51??61
????????????12?12?14?19??26??58??60??55
????????????14?13?16?24??40??57??69??56
????????????14?17?22?29??51??87??80??62
????????????18?22?37?56??68?109?103??77
????????????24?35?55?64??81?104?113??92
????????????49?64?78?87?103?121?120?101
????????????72?92?95?98?112?100?103?99]）;

????%?I?am?interested?in?the?energy?of?the?dct?coefficients?I?will?use?
????%?this?matrix?（found?from?long?observation）?to?select?dct?coefficients.
????%?lowest?number?->?highest?priority
????dct_coefficient_priority_8x8?=[
???????????1???2???6???7??15??16??28??29;
???????????3???5???8??14??17??27??30??43;
???????????4???9??13??18??26??31??42??44;
??????????10??12??19??25??32??41??45??54;
??????????11??20??24??33??40??46??53??55;
??????????21??23??34??39??47??52??56??61;
??????????22??35??38??48??51??57??60??62;
??????????36??37??49??50??58??59??63??64];
????%?if?we?decide?to?take?10?coefficients?with?the?most?energy?we?will?assign?
????%?99?to?ignore?the?other?coefficients?and?remain?with?a?matrix?of?8x8

????%This?suitable?Zigzag?order?is?formed?from?the??JPEG?standard
????ZigZag_Order?=?uint8（[
????????????1??9??2??3??10?17?25?18
????????????11?4??5??12?19?26?33?41
????????????34?27?20?13?6??7??14?21?
????????????28?35?42?49?57?50?43?36?
????????????29?22?15?8??16?23?30?37
????????????44?51?58?59?52?45?38?31?
????????????24?32?39?46?53?60?61?54?
????????????47?40?48?55?62?63?56?64]）;

????%?Finding?the?reverse?zigzag?order?（8x8?matrix）
????reverse_zigzag_order_8x8?=?zeros（88）;
????for?k?=?1:（size（ZigZag_Order1）?*size（ZigZag_Order2））?
????????reverse_zigzag_order_8x8（k）?=?find（ZigZag_Order==?k）;?
????end;
????????????????????
????Compressed_image_size=0;
????%---------------------------------------------------------------------

????
close?all;

for?Image_Index?=?8:8????%?the?whole?program?will?be?tested?for?9?images?（0->8）
???figure;??????????%keep?the?input-output?for?each?image?s

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2007-06-20?14:17??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\
?????文件???????16720??2003-01-13?17:18??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\0.tif
?????文件???????16570??2003-01-08?16:31??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\1.tif
?????文件????????3878??2003-01-08?16:33??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\2.tif
?????文件????????2863??2003-01-08?16:34??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\3.tif
?????文件????????3547??2003-01-08?16:35??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\4.tif
?????文件????????1996??2003-01-08?16:35??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\5.tif
?????文件????????3936??2003-01-08?16:39??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\6.TIF
?????文件????????3863??2003-01-08?16:37??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\7.tif
?????文件????????4200??2003-01-08?16:37??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\8.tif
?????文件???????25680??2007-06-18?13:47??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\jpeg.asv
?????文件???????25776??2007-06-18?13:50??JPEG?Encoder?Decoder\JPEG?Encoder?Decoder\jpeg.m
?????目錄???????????0??2007-06-20?14:17??JPEG?Encoder?Decoder\