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KJpegDecode.c：源码内容
							//---------------------------------------------------------------------------
// Sword3 Engine (c) 1999-2000 by Kingsoft
//
// File:	KJpegDeocode.cpp
// Date:	2000.08.08
// Code:	Daniel Wang
// Desc:	Jpeg DU Decode
// From:	Cloud Wu's JPEG Decoder
//---------------------------------------------------------------------------
#include <windows.h>
#include "KJpegLib.h"
/****************************************************************************	
DU 的解码
每个 DU 里的数据按下面次序(倒序)重排列过, 得到原始次序
BYTE jpeg_zigzag[64] = {
	0, 63,62,55,47,54,61,60,
	53,46,39,31,38,45,52,59,
	58,51,44,37,30,23,15,22,
	29,36,43,50,57,56,49,42,
	35,28,21,14,7, 6, 13,20,
	27,34,41,48,40,33,26,19,
	12,5, 4,11,18,25,32,24,
	17,10,3,2, 9, 16,8, 1 
};
****************************************************************************/
// ANN 算法需要转置矩阵
BYTE jpeg_zigzag[64] = {
	0,63,55,62,61,54,47,39,
	46,53,60,59,52,45,38,31,
	23,30,37,44,51,58,57,50,
	43,36,29,22,15,7,14,21,
	28,35,42,49,56,48,41,34,
	27,20,13,6,5,12,19,26,
	33,40,32,25,18,11,4,3,
	10,17,24,16,9,2,1,8
};
//---------------------------------------------------------------------------
// 函数:	jpeg_Preprocess
// 功能:	预处理, 去掉 0xFF
// 参数:	stream		JPEG数据流
// 返回:	void
//---------------------------------------------------------------------------
void jpeg_preprocess(LPBYTE stream)
{
	__asm
	{
		mov esi,stream;
		mov edi,stream;
		cld;
		ALIGN 4
_loop:
		lodsb;
		cmp al,0xff;
		jz _getFF;
		stosb;
		jmp _loop;
_getFF:
		lodsb;
		test al,al;
		jnz _not0;
		mov byte ptr [edi],0xff;
		inc edi;
		jmp _loop;
_not0:
		cmp al,0xd9;	// 结束?
		jz _end;
		cmp al,0xff;
		jz _getFF;
_end:
	}
}
//---------------------------------------------------------------------------
// 函数:	jpeg_decode_DU
// 功能:	从数据流 jpeg_stream 解码一个 DU 到 buf
// 参数:	buf		解码后的缓存
//			com		jpeg componet
// 返回:	void
//---------------------------------------------------------------------------
void jpeg_decode_DU(short *buf, int com)
{
	short*			QTB = jpeg_qtable[jpeg_head.component[com].qtb];
	JPEG_HTABLE*	ACT = &jpeg_htable[jpeg_head.component[com].act];
	JPEG_HTABLE*	DCT = &jpeg_htable[jpeg_head.component[com].dct];
	short			JpegDC = jpeg_DC[com];
	// DC 的解码
	__asm
	{
		mov edx,DCT;
		mov esi,jpeg_stream;
		mov edi,QTB;
		cld;
		mov ch,byte ptr[edx+JPEG_HTABLE.num];
		mov edx,[edx]JPEG_HTABLE.htb;
		mov cl,jpeg_bit;
		lodsd;
		mov ebx,eax;
		mov eax,[esi];
		bswap ebx;
		bswap eax;
		shld ebx,eax,cl;
_loop_dct:
		mov cl,[edx]JPEG_HCODE.len;
		xor eax,eax;
		shld eax,ebx,cl;
		cmp ax,[edx]JPEG_HCODE.code;
		jz _decode_dct;
		add edx,4;
		dec ch;
		jmp _loop_dct;
_decode_dct:
		mov ch,cl;
		mov cl,jpeg_bit;	// 刚才用掉 cl 个bit
		shr ebx,cl;
		add cl,ch; // 一共用掉 bit 数
		cmp cl,32; // 用完 4 字节?
		jl _lt4byte_dc;
		sub cl,32;
		lodsd;
		bswap eax;
		mov ebx,eax;
_lt4byte_dc:
		mov eax,[esi];
		bswap eax;
		shld ebx,eax,cl;
		mov ch,cl;
		mov cl,[edx]JPEG_HCODE.num;
		xor eax,eax;
		shld eax,ebx,cl;
		xchg ch,cl;
		shr ebx,cl;
		add cl,ch;
		xchg ch,cl;
		dec cl;
		bt eax,cl;
		jc _get_diff;
		inc cl;
		mov edx,1;
		inc eax;
		shl edx,cl;
		sub eax,edx;
_get_diff:
		add ax,JpegDC;
		mov edx,com;
		mov cl,ch;
		push edi;
		lea edi,jpeg_DC;
		mov [edi + edx * 2],ax;
		pop edi;
		imul word ptr[edi];
		mov edx,buf;
		add edi,2;
		mov [edx],ax;
// AC 的解码. cl 是前面被使用掉的 bit 数, ebx 是上4byte 
		cmp cl,32;	// 用完 4 字节?
		jl _lt4byte_dc0;
		sub cl,32;
		lodsd;
		bswap eax;
		mov ebx,eax;
_lt4byte_dc0:
		mov eax,[esi];
		bswap eax;
		shld ebx,eax,cl;
		mov jpeg_bit,cl;	//用掉 cl 个 bit
		mov cx,63;	// 处理 63 个 AC
_loop_decode_act:
		mov edx,ACT;
		bswap ecx;
		mov ch,byte ptr[edx+JPEG_HTABLE.num];
		mov edx,[edx]JPEG_HTABLE.htb;
_loop_act:
		mov cl,[edx]JPEG_HCODE.len;
		xor eax,eax;
		shld eax,ebx,cl;
		cmp ax,[edx]JPEG_HCODE.code;
		jz _decode_act;
		add edx,4;
		dec ch;
		jmp _loop_act;
_decode_act:
// [edx]JPEG_HCODE.num 是接出来的码
		mov ch,cl;
		mov cl,jpeg_bit;	// 刚才用掉 cl 个bit
		shr ebx,cl;
		add cl,ch; // 一共用掉 bit 数
		cmp cl,32;	// 用完 4 字节?
		jl _lt4byte;
		sub cl,32;
		lodsd;
		bswap eax;
		mov ebx,eax;
_lt4byte:
		mov eax,[esi];
		bswap eax;
		shld ebx,eax,cl;
		mov jpeg_bit,cl;//使用了下4byte的 cl bit
		movzx eax,byte ptr[edx]JPEG_HCODE.num;
		bswap ecx;
		test ax,ax;
		jz _decode_end;
		ror eax,4;
		cmp cx,ax;
		jz _decode_end;
		sub cx,ax;
		rol eax,4;
		bswap ecx;
		mov cl,al;
		mov ch,al;
		and cl,0xf;
		shr ch,4;
		jz _skip_set0;
		movzx eax,ch;
		bswap ecx;
		lea edi,[edi+2*eax];
		add ax,cx;
		bswap ecx;
_set0:
		movzx edx,[eax+jpeg_zigzag];
		add edx,edx;
		add edx,buf;
		dec eax;
		dec ch;
		mov word ptr[edx],0;
		jnz _set0;
_skip_set0:
		xor eax,eax;
		shld eax,ebx,cl;
		dec cl;
		bt eax,cl;
		jc _get_ac;
		mov edx,2;
		inc eax;
		shl edx,cl;
		sub eax,edx;
_get_ac:
		inc cl;
		imul word ptr[edi];
// dx==0 时, 正数,无进位
		test dx,dx;
		jz _2byte;
// dx==0xffff 时, 负数,无进位
		inc dx;
		jz _2byte;
		mov ax,0x7fff;
		bt dx,15;
		adc ax,0;
_2byte:
		bswap ecx;
		movzx edx,cx;
		movzx edx,[edx+jpeg_zigzag];
		add edx,edx
		add edx,buf;
		add edi,2;
		mov [edx],ax;
		bswap ecx;
		mov ch,cl;
		mov cl,jpeg_bit;
		shr ebx,cl;
		add cl,ch;	// 累计使用 bit 数
		cmp cl,32;	// 用完 4 字节?
		jl _lt4byte_2;
		sub cl,32;
		lodsd;
		bswap eax;
		mov ebx,eax;
_lt4byte_2:
		mov eax,[esi];
		bswap eax;
		shld ebx,eax,cl;
		mov jpeg_bit,cl;//使用了下4byte的 cl bit
		bswap ecx;
		dec cx;
		jnz _loop_decode_act;
		jmp _end;
_decode_end:
		movzx ecx,cx;
		xor eax,eax;
		mov edi,buf;
_end_loop:
		movzx edx,[ecx+jpeg_zigzag];
		dec ecx;
		mov [edi+edx*2],ax;
		jnz _end_loop;
_end:
		sub esi,4;
		mov jpeg_stream,esi;
	}
	
	// iDCT 解码
	jpeg_IDCT(buf);
}
//---------------------------------------------------------------------------

						