dct.c

经过优化的嵌入式系统开源JPEG编解码库；

#include "ejpgl.h"

extern signed int weights[512];
signed short dctresult[MATRIX_SIZE][MATRIX_SIZE];

int dct_init_start() {

	return 0;

}

int	dct_stop_done() {

	return 0;
	
}

/*
	Function Name: dct

	Operation: Find the 8x8 DCT of an array using separable DCT
	First, finds 1-d DCT along rows, storing the result in inter[][]
	Then, 1-d DCT along columns of inter[][] is found

	Input: pixels is the 8x8 input array

	Output: dct is the 8x8 output array
*/

void dct(signed char pixels[8][8], int color)
{
	int inr, inc; 		/* rows and columns of input image */
	int intr, intc;		/* rows and columns of intermediate image */
	int outr, outc;		/* rows and columns of dct */
	int f_val;		/* cumulative sum */
	int inter[8][8];	/* stores intermediate result */
	int i,j,k;
        k=0;

 	for (intr=0; intr<8; intr++)
		for (intc=0; intc<8; intc++) {
			for (i=0,f_val=0; i<8; i++) {
				f_val += (pixels[intr][i]* weights[k]);//cos((double)(2*i+1)*(double)intc*PI/16);
                            k++;
			}
                     if (intc!=0) inter[intr][intc] =  f_val>>15;
                     else inter[intr][intc] =  (11585*(f_val>>14))>>15;

                }

	/* find 1-d dct along columns */

 	for (outc=0, k=0; outc<8; outc++)
		for (outr=0; outr<8; outr++) {
			for (i=0,f_val=0; i<8; i++) {
				f_val += (inter[i][outc] *weights[k]);
                            k++;
			}
                     if (outr!=0) dctresult[outr][outc] = f_val>>15;
                     else dctresult[outr][outc] = (11585*(f_val>>14)>>15);
		}

	zzq_encode(dctresult, color);
	return;

}


signed int weights[512] = {
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16069,
13623,
9102,
3196,
-3196,
-9102,
-13623,
-16069,
15137,
6270,
-6270,
-15137,
-15137,
-6270,
6270,
15137,
13623,
-3196,
-16069,
-9103,
9102,
16069,
3196,
-13623,
11585,
-11585,
-11585,
11585,
11585,
-11585,
-11585,
11585,
9102,
-16069,
3196,
13623,
-13623,
-3197,
16069,
-9102,
6270,
-15137,
15137,
-6270,
-6270,
15137,
-15137,
6270,
3196,
-9103,
13623,
-16069,
16069,
-13623,
9102,
-3196,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16069,
13623,
9102,
3196,
-3196,
-9102,
-13623,
-16069,
15137,
6270,
-6270,
-15137,
-15137,
-6270,
6270,
15137,
13623,
-3196,
-16069,
-9103,
9102,
16069,
3196,
-13623,
11585,
-11585,
-11585,
11585,
11585,
-11585,
-11585,
11585,
9102,
-16069,
3196,
13623,
-13623,
-3197,
16069,
-9102,
6270,
-15137,
15137,
-6270,
-6270,
15137,
-15137,
6270,
3196,
-9103,
13623,
-16069,
16069,
-13623,
9102,
-3196,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16069,
13623,
9102,
3196,
-3196,
-9102,
-13623,
-16069,
15137,
6270,
-6270,
-15137,
-15137,
-6270,
6270,
15137,
13623,
-3196,
-16069,
-9103,
9102,
16069,
3196,
-13623,
11585,
-11585,
-11585,
11585,
11585,
-11585,
-11585,
11585,
9102,
-16069,
3196,
13623,
-13623,
-3197,
16069,
-9102,
6270,
-15137,
15137,
-6270,
-6270,
15137,
-15137,
6270,
3196,
-9103,
13623,
-16069,
16069,
-13623,
9102,
-3196,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16069,
13623,
9102,
3196,
-3196,
-9102,
-13623,
-16069,
15137,
6270,
-6270,
-15137,
-15137,
-6270,
6270,
15137,
13623,
-3196,
-16069,
-9103,
9102,
16069,
3196,
-13623,
11585,
-11585,
-11585,
11585,
11585,
-11585,
-11585,
11585,
9102,
-16069,
3196,
13623,
-13623,
-3197,
16069,
-9102,
6270,
-15137,
15137,
-6270,
-6270,
15137,
-15137,
6270,
3196,
-9103,
13623,
-16069,
16069,
-13623,
9102,
-3196,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16069,
13623,
9102,
3196,
-3196,
-9102,
-13623,
-16069,
15137,
6270,
-6270,
-15137,
-15137,
-6270,
6270,
15137,
13623,
-3196,
-16069,
-9103,
9102,
16069,
3196,
-13623,
11585,
-11585,
-11585,
11585,
11585,
-11585,
-11585,
11585,
9102,
-16069,
3196,
13623,
-13623,
-3197,
16069,
-9102,
6270,
-15137,
15137,
-6270,
-6270,
15137,
-15137,
6270,
3196,
-9103,
13623,
-16069,
16069,
-13623,
9102,
-3196,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16069,
13623,
9102,
3196,
-3196,
-9102,
-13623,
-16069,
15137,
6270,
-6270,
-15137,
-15137,
-6270,
6270,
15137,
13623,
-3196,
-16069,
-9103,
9102,
16069,
3196,
-13623,
11585,
-11585,
-11585,
11585,
11585,
-11585,
-11585,
11585,
9102,
-16069,
3196,
13623,
-13623,
-3197,
16069,
-9102,
6270,
-15137,
15137,
-6270,
-6270,
15137,
-15137,
6270,
3196,
-9103,
13623,
-16069,
16069,
-13623,
9102,
-3196,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16069,
13623,
9102,
3196,
-3196,
-9102,
-13623,
-16069,
15137,
6270,
-6270,
-15137,
-15137,
-6270,
6270,
15137,
13623,
-3196,
-16069,
-9103,
9102,
16069,
3196,
-13623,
11585,
-11585,
-11585,
11585,
11585,
-11585,
-11585,
11585,
9102,
-16069,
3196,
13623,
-13623,
-3197,
16069,
-9102,
6270,
-15137,
15137,
-6270,
-6270,
15137,
-15137,
6270,
3196,
-9103,
13623,
-16069,
16069,
-13623,
9102,
-3196,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16384,
16069,
13623,
9102,
3196,
-3196,
-9102,
-13623,
-16069,
15137,
6270,
-6270,
-15137,
-15137,
-6270,
6270,
15137,
13623,
-3196,
-16069,
-9103,
9102,
16069,
3196,
-13623,
11585,
-11585,
-11585,
11585,
11585,
-11585,
-11585,
11585,
9102,
-16069,
3196,
13623,
-13623,
-3197,
16069,
-9102,
6270,
-15137,
15137,
-6270,
-6270,
15137,
-15137,
6270,
3196,
-9103,
13623,
-16069,
16069,
-13623,
9102,
-3196
};