【正文】 nrline_up,nrline_dn++){memcpy(tmpline,RGB_buffer+nrline_up*Ximage,dimline)。//Reorder in memory the inversed bitmapfor(nrline_up=Yimage1,nrline_dn=0。tmpline=(colorRGB *)malloc(dimline)。}}Ximage=Xdiv8。column++){memcpy(RGB_buffernrline*Xdiv8+column,amp。for(column=Ximage。memcpy(amp。nrline++){fread(RGB_buffer+nrline*Xdiv8,1,Ximage*3,fp_bitmap)。for(nrline=0。if(Ximage%4!=0) nr_fillingbytes=4(Ximage%4)。// The image we encode shall be filled with the last line and the last column // from the original bitmap, until Ximage and Yimage are divisible by 8 // Load BMP image from disk and plete X RGB_buffer=(colorRGB*) (malloc(3*Xdiv8*Ydiv8)) 。if(Yimage%8!=0) Ydiv8=(Yimage/8)*8+8。//Keep the old dimensions// of the imageif(Ximage%8!=0)Xdiv8=(Ximage/8)*8*8。*Ximage_original=Ximage。Ximage=(WORD)TMPBUF[19]*256^TMPBUF[18]。M39。B39。if(fread(TMPBUF,1,54,fp_bitmap)!=54)exitmessage(Need a truecolor BMP to encode.)。FILE *fp_bitmap=fopen(bitmap_name,rb)。WORD dimline。BYTE TMPBUF[256]。//The number of the filling bytes in the BMP file// (the dimension in bytes of a BMP line on the disk is divisible by 4)colorRGB lastcolor。}}void load_bitmap(char *bitmap_name, WORD *Ximage_original,WORD *Yimage_original){WORD Xdiv8,Ydiv8。process_DU(CrDU,fdtbl_Cb,amp。process_DU(CbDU,fdtbl_Cb,amp。process_DU(YDU,fdtbl_Y,amp。xposXimage。yposYimage。//DC coefficients used for differential encoding WORD xpos,ypos。}location+=Ximage8。location++。CbDU[pos]=Cb(R,G,B)。B=RGB_buffer[location].B。x++){R=RGB_buffer[location].R。y++){for(x=0。for(y=0。BYTE R,G,B。BYTE pos=0。}if(endOpos!=63)writebits(EOB)。}writebits(HTAC[nrzeroes*16+category[DU[i]]])。nrmarker++)writebits(M16zeroes)。if(nrzeroes=16){for(nrmarker=1。i++)。amp。for(。}i=1。//endOpos=first element in reverse order !=0 if(endOpos==0){writebits(EOB)。(DU[endOpos]==0)。(endOpos0)amp。 writebits(bitcode[Diff])。//Encode DCif(Diff=0) writebits(HTDC[0])。Diff=DU[0]*DC。i=63。fdct_and_quantization(ComponentDU,fdtbl,DU_DCT)。BYTE nrmarker。BYTE endOpos。BYTE i。}}void process_DU(SBYTE *ComponentDU,float *fdtbl,SWORD *DC,bitstring *HTDC,bitstring *HTAC){bitstring EOB=HTAC[0x00]。i++){/* Apply the quantization and scaling factor */temp=datafloat[i]*fdtbl[i]。 /* advance pointer to next column */}// Quantize/descale the coefficients, and store into output array for(i=0。dataptr[56]=z11z4。/* phase 6 */ dataptr[24]=z13z2。/* phase 5 */ z13=tmp7z3。/* c2+c6 */ z3=tmp11*((float))。/* c6 */ z2=((float))*tmp10+z5。tmp12=tmp6+tmp7。/* Odd part */tmp10=tmp4+tmp5。/*c4*/dataptr[16]=tmp13+z1。 /* phase 3 */ dataptr[32]=tmp10tmp11。tmp12=tmp1tmp2。 /* phase 2 */ tmp13=tmp0tmp3。tmp4=dataptr[24]dataptr[32]。tmp5=dataptr[16]dataptr[40]。tmp6=dataptr[8]dataptr[48]。tmp7=dataptr[0]dataptr[56]。ctr=0。/* advance pointer to next row */}/* Pass 2: process columns. */dataptr=datafloat。dataptr[7]=z11z4。/* phase 6 */ dataptr[3]=z13z2。/* phase 5 */z13=tmp7z3。/*c2+c6 */ z3=tmp11*((float))。/* c6 */ z2=((float))*tmp10+z5。tmp12=tmp6+tmp7。/* Odd part */tmp10=tmp4+tmp5。/* c4 */ dataptr[2]=tmp13+z1。/* phase 3 */ dataptr[4]=tmp10tmp11。tmp12=tmp1tmp2。/*phase 2 */ tmp13=tmp0tmp3。tmp4=dataptr[3]dataptr[4]。tmp5=dataptr[2]dataptr[5]。tmp6=dataptr[1]dataptr[6]。tmp7=dataptr[0]dataptr[7]。ctr=0。/* Pass 1: process rows. */ dataptr=datafloat。i64。BYTE i。float temp。float *dataptr。float tmp10,tmp11,tmp12,tmp13。i++。col++){fdtbl_Y[i]=(float)(((double)[zigzag[i]]*aanscalefactor[row]*aanscalefactor[col]*))。row++){ for(col=0。for (row=0。BYTE row, col。N IDCT method, divisors are equal to quantization coefficients scaled by scalefactor[row]*scalefactor[col], where scalefactor[0] = 1scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=l. .7 We apply a further scale factor of 8.What39。 s C source:// Forward DCT routine idea taken from Independent JPEG Group39。CrBtab[B]=(SDWORD)(65536*+)*B。B++) {YBtab[B]=(SDWORD)(65536*+)*B。}for(B=0。CbGtab[G]=(SDWORD)(65536*+)*G。G=255。CrRtab[R]=(SDWORD)(32768)*R 。R++) {YRtab[R]=(SDWORD)(65536*+)*R。for(R=0。nrupper=1。bitcode[nr].value=(WORD)(nrupper1+nr)。nr++){category[nr]=cat。}//Negative numbersfor(nr=(nrupper1)。bitcode[nr].length=cat。nrnrupper。cat=15。nrupper=2。bitcode=bitcode_alloc+32767。//allow negative subscripts bitcode_alloc=(bitstring *)malloc(65535*sizeof(bitstring))。if(category_alloc=NULL)exitmessage(Not enough memory.)。BYTE cat,value。}void set_numbers_category_and_bitcode(){SDWORD nr。}void exitmessage(char *error_message){printf(%s\n,error_message)。pute_Huffman_table(std_ac_luminance_nrcodes,std_ac_luminance_values,YAC_HT)。}}void init_Huffman_tables(){pute_Huffman_table(std_dc_luminance_nrcodes,std_dc_luminance_values,YDC_HT)。codevalue++。HT[std_table[pos_in_table]].length=k。j=nrcodes[k]。k=16。pos_in_table=0。WORD codevalue。}}}void pute_Huffman_table(BYTE *nrcodes,BYTE *std_table,bitstring *HT){BYTE k, j。}bytepos=7。writebyte(0)。bytepos。 mask[posval]) bytenew|=mask[bytepos]。posval=。SBYTE posval。}void writebits(bitstring bs)// A portable version。ilength。writeword(length+2)。writeword(0xFFFE)。writebyte()。writebyte()。writebyte()。writebyte()。writebyte()。writeword()。i++) [i]=std_ac_chrominance_values[i]。for(i=0。i16。=0x11。i=11。i++) [i]=std_dc_chrominance_nrcodes[i+1]。for(i=0。i++) [i]=std_ac_luminance_values[i]。for (i=0。i16。=0x10。i=11。i++) [i]=std_dc_luminance_nrcodes[i+1]。for(i=0。=0x01A2。}void set_DHTinfo(){BYTE i。i=161。i++) writebyte([i])。for(i=0。i++) writebyte([i])。for(i=0。i16。writebyte()。i=161。i++) writebyte([i])。for(i=0。i++) writebyte([i])。for(i=0。i16。writebyte()。writeword()。set_quant_table(std_chrominance_qt,scalefactor,)。=1。=132。ll get, and the smaller // pression we39。}}void set_DQTinfo