jidctred.cpp File Reference

#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"

Include dependency graph for jidctred.cpp:

Macros
#define	JPEG_INTERNALS
#define	CONST_BITS   13
#define	PASS1_BITS   2
#define	FIX_0_211164243   ((int32_t) 1730) /* FIX(0.211164243) */
#define	FIX_0_509795579   ((int32_t) 4176) /* FIX(0.509795579) */
#define	FIX_0_601344887   ((int32_t) 4926) /* FIX(0.601344887) */
#define	FIX_0_720959822   ((int32_t) 5906) /* FIX(0.720959822) */
#define	FIX_0_765366865   ((int32_t) 6270) /* FIX(0.765366865) */
#define	FIX_0_850430095   ((int32_t) 6967) /* FIX(0.850430095) */
#define	FIX_0_899976223   ((int32_t) 7373) /* FIX(0.899976223) */
#define	FIX_1_061594337   ((int32_t) 8697) /* FIX(1.061594337) */
#define	FIX_1_272758580   ((int32_t) 10426) /* FIX(1.272758580) */
#define	FIX_1_451774981   ((int32_t) 11893) /* FIX(1.451774981) */
#define	FIX_1_847759065   ((int32_t) 15137) /* FIX(1.847759065) */
#define	FIX_2_172734803   ((int32_t) 17799) /* FIX(2.172734803) */
#define	FIX_2_562915447   ((int32_t) 20995) /* FIX(2.562915447) */
#define	FIX_3_624509785   ((int32_t) 29692) /* FIX(3.624509785) */
#define	MULTIPLY(var, const)   MULTIPLY16C16(var,const)
#define	DEQUANTIZE(coef, quantval)   (((ISLOW_MULT_TYPE) (coef)) * (quantval))

Functions
void	jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
void	jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
void	jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)

Macro Definition Documentation

#define JPEG_INTERNALS

#define CONST_BITS   13

#define PASS1_BITS   2

#define FIX_0_211164243   ((int32_t) 1730) /* FIX(0.211164243) */

#define FIX_0_509795579   ((int32_t) 4176) /* FIX(0.509795579) */

#define FIX_0_601344887   ((int32_t) 4926) /* FIX(0.601344887) */

#define FIX_0_720959822   ((int32_t) 5906) /* FIX(0.720959822) */

#define FIX_0_765366865   ((int32_t) 6270) /* FIX(0.765366865) */

#define FIX_0_850430095   ((int32_t) 6967) /* FIX(0.850430095) */

#define FIX_0_899976223   ((int32_t) 7373) /* FIX(0.899976223) */

#define FIX_1_061594337   ((int32_t) 8697) /* FIX(1.061594337) */

#define FIX_1_272758580   ((int32_t) 10426) /* FIX(1.272758580) */

#define FIX_1_451774981   ((int32_t) 11893) /* FIX(1.451774981) */

#define FIX_1_847759065   ((int32_t) 15137) /* FIX(1.847759065) */

#define FIX_2_172734803   ((int32_t) 17799) /* FIX(2.172734803) */

#define FIX_2_562915447   ((int32_t) 20995) /* FIX(2.562915447) */

#define FIX_3_624509785   ((int32_t) 29692) /* FIX(3.624509785) */

#define MULTIPLY	(		var,
			const
	)		MULTIPLY16C16(var,const)

#define DEQUANTIZE	(		coef,
			quantval
	)		(((ISLOW_MULT_TYPE) (coef)) * (quantval))

Function Documentation

void jpeg_idct_4x4	(	j_decompress_ptr	cinfo,
		jpeg_component_info *	compptr,
		JCOEFPTR	coef_block,
		JSAMPARRAY	output_buf,
		JDIMENSION	output_col
	)

{
  int32_t tmp0, tmp2, tmp10, tmp12;
  int32_t z1, z2, z3, z4;
  JCOEFPTR inptr;
  ISLOW_MULT_TYPE * quantptr;
  int * wsptr;
  JSAMPROW outptr;
  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
  int ctr;
  int workspace[DCTSIZE*4]; /* buffers data between passes */
  SHIFT_TEMPS

  /* Pass 1: process columns from input, store into work array. */

  inptr = coef_block;
  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
  wsptr = workspace;
  for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
    /* Don't bother to process column 4, because second pass won't use it */
    if (ctr == DCTSIZE-4)
      continue;
    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
    inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 &&
    inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) {
      /* AC terms all zero; we need not examine term 4 for 4x4 output */
      int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
      
      wsptr[DCTSIZE*0] = dcval;
      wsptr[DCTSIZE*1] = dcval;
      wsptr[DCTSIZE*2] = dcval;
      wsptr[DCTSIZE*3] = dcval;
      
      continue;
    }
    
    /* Even part */
    
    tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
    tmp0 <<= (CONST_BITS+1);
    
    z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
    z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);

    tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);
    
    tmp10 = tmp0 + tmp2;
    tmp12 = tmp0 - tmp2;
    
    /* Odd part */
    
    z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
    z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
    z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
    z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
    
    tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
     + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
     + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
     + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
    
    tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
     + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
     + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
     + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

    /* Final output stage */
    
    wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
    wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
    wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
    wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
  }
  
  /* Pass 2: process 4 rows from work array, store into output array. */

  wsptr = workspace;
  for (ctr = 0; ctr < 4; ctr++) {
    outptr = output_buf[ctr] + output_col;
    /* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
    if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
    wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
      /* AC terms all zero */
      JSAMPLE dcval = range_limit[(int) DESCALE((int32_t) wsptr[0], PASS1_BITS+3)
                  & RANGE_MASK];
      
      outptr[0] = dcval;
      outptr[1] = dcval;
      outptr[2] = dcval;
      outptr[3] = dcval;
      
      wsptr += DCTSIZE;     /* advance pointer to next row */
      continue;
    }
#endif
    
    /* Even part */
    
    tmp0 = ((int32_t) wsptr[0]) << (CONST_BITS+1);
    
    tmp2 = MULTIPLY((int32_t) wsptr[2], FIX_1_847759065)
     + MULTIPLY((int32_t) wsptr[6], - FIX_0_765366865);
    
    tmp10 = tmp0 + tmp2;
    tmp12 = tmp0 - tmp2;
    
    /* Odd part */
    
    z1 = (int32_t) wsptr[7];
    z2 = (int32_t) wsptr[5];
    z3 = (int32_t) wsptr[3];
    z4 = (int32_t) wsptr[1];
    
    tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
     + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
     + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
     + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
    
    tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
     + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
     + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
     + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

    /* Final output stage */
    
    outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
                      CONST_BITS+PASS1_BITS+3+1)
                & RANGE_MASK];
    outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
                      CONST_BITS+PASS1_BITS+3+1)
                & RANGE_MASK];
    outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
                      CONST_BITS+PASS1_BITS+3+1)
                & RANGE_MASK];
    outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
                      CONST_BITS+PASS1_BITS+3+1)
                & RANGE_MASK];
    
    wsptr += DCTSIZE;       /* advance pointer to next row */
  }
}

void jpeg_idct_2x2	(	j_decompress_ptr	cinfo,
		jpeg_component_info *	compptr,
		JCOEFPTR	coef_block,
		JSAMPARRAY	output_buf,
		JDIMENSION	output_col
	)

{
  int32_t tmp0, tmp10, z1;
  JCOEFPTR inptr;
  ISLOW_MULT_TYPE * quantptr;
  int * wsptr;
  JSAMPROW outptr;
  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
  int ctr;
  int workspace[DCTSIZE*2]; /* buffers data between passes */
  SHIFT_TEMPS

  /* Pass 1: process columns from input, store into work array. */

  inptr = coef_block;
  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
  wsptr = workspace;
  for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
    /* Don't bother to process columns 2,4,6 */
    if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6)
      continue;
    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 &&
    inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) {
      /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
      int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
      
      wsptr[DCTSIZE*0] = dcval;
      wsptr[DCTSIZE*1] = dcval;
      
      continue;
    }
    
    /* Even part */
    
    z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
    tmp10 = z1 << (CONST_BITS+2);
    
    /* Odd part */

    z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
    tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
    z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
    tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
    z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
    tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
    z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
    tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

    /* Final output stage */
    
    wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
    wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
  }
  
  /* Pass 2: process 2 rows from work array, store into output array. */

  wsptr = workspace;
  for (ctr = 0; ctr < 2; ctr++) {
    outptr = output_buf[ctr] + output_col;
    /* It's not clear whether a zero row test is worthwhile here ... */

#ifndef NO_ZERO_ROW_TEST
    if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
      /* AC terms all zero */
      JSAMPLE dcval = range_limit[(int) DESCALE((int32_t) wsptr[0], PASS1_BITS+3)
                  & RANGE_MASK];
      
      outptr[0] = dcval;
      outptr[1] = dcval;
      
      wsptr += DCTSIZE;     /* advance pointer to next row */
      continue;
    }
#endif
    
    /* Even part */
    
    tmp10 = ((int32_t) wsptr[0]) << (CONST_BITS+2);
    
    /* Odd part */

    tmp0 = MULTIPLY((int32_t) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
     + MULTIPLY((int32_t) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
     + MULTIPLY((int32_t) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
     + MULTIPLY((int32_t) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

    /* Final output stage */
    
    outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
                      CONST_BITS+PASS1_BITS+3+2)
                & RANGE_MASK];
    outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
                      CONST_BITS+PASS1_BITS+3+2)
                & RANGE_MASK];
    
    wsptr += DCTSIZE;       /* advance pointer to next row */
  }
}

void jpeg_idct_1x1	(	j_decompress_ptr	cinfo,
		jpeg_component_info *	compptr,
		JCOEFPTR	coef_block,
		JSAMPARRAY	output_buf,
		JDIMENSION	output_col
	)

{
  int dcval;
  ISLOW_MULT_TYPE * quantptr;
  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
  SHIFT_TEMPS

  /* We hardly need an inverse DCT routine for this: just take the
   * average pixel value, which is one-eighth of the DC coefficient.
   */
  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
  dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
  dcval = (int) DESCALE((int32_t) dcval, 3);

  output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
}