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The Independent JPEG Group's JPEG software v4a

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This commit is contained in:
Thomas G. Lane
1993-02-18 00:00:00 +00:00
committed by DRC
parent 88aeed428f
commit cc7150e281
42 changed files with 1083 additions and 451 deletions
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212
jquant2.c
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@@ -1,7 +1,7 @@
/*
* jquant2.c
*
* Copyright (C) 1991, 1992, Thomas G. Lane.
* Copyright (C) 1991, 1992, 1993, Thomas G. Lane.
* This file is part of the Independent JPEG Group's software.
* For conditions of distribution and use, see the accompanying README file.
*
@@ -875,36 +875,39 @@ pass2_nodither (decompress_info_ptr cinfo, int num_rows,
/* Declarations for Floyd-Steinberg dithering.
*
* Errors are accumulated into the arrays evenrowerrs[] and oddrowerrs[].
* These have resolutions of 1/16th of a pixel count. The error at a given
* pixel is propagated to its unprocessed neighbors using the standard F-S
* fractions,
* Errors are accumulated into the array fserrors[], at a resolution of
* 1/16th of a pixel count. The error at a given pixel is propagated
* to its not-yet-processed neighbors using the standard F-S fractions,
* ... (here) 7/16
* 3/16 5/16 1/16
* We work left-to-right on even rows, right-to-left on odd rows.
*
* Each of the arrays has (#columns + 2) entries; the extra entry
* at each end saves us from special-casing the first and last pixels.
* Each entry is three values long.
* In evenrowerrs[], the entries for a component are stored left-to-right, but
* in oddrowerrs[] they are stored right-to-left. This means we always
* process the current row's error entries in increasing order and the next
* row's error entries in decreasing order, regardless of whether we are
* working L-to-R or R-to-L in the pixel data!
* We can get away with a single array (holding one row's worth of errors)
* by using it to store the current row's errors at pixel columns not yet
* processed, but the next row's errors at columns already processed. We
* need only a few extra variables to hold the errors immediately around the
* current column. (If we are lucky, those variables are in registers, but
* even if not, they're probably cheaper to access than array elements are.)
*
* The fserrors[] array has (#columns + 2) entries; the extra entry at
* each end saves us from special-casing the first and last pixels.
* Each entry is three values long, one value for each color component.
*
* Note: on a wide image, we might not have enough room in a PC's near data
* segment to hold the error arrays; so they are allocated with alloc_medium.
* segment to hold the error array; so it is allocated with alloc_medium.
*/
#ifdef EIGHT_BIT_SAMPLES
typedef INT16 FSERROR; /* 16 bits should be enough */
typedef int LOCFSERROR; /* use 'int' for calculation temps */
#else
typedef INT32 FSERROR; /* may need more than 16 bits? */
typedef INT32 FSERROR; /* may need more than 16 bits */
typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */
#endif
typedef FSERROR FAR *FSERRPTR; /* pointer to error array (in FAR storage!) */
static FSERRPTR evenrowerrs, oddrowerrs; /* current-row and next-row errors */
static FSERRPTR fserrors; /* accumulated errors */
static boolean on_odd_row; /* flag to remember which row we are on */
@@ -913,18 +916,15 @@ pass2_dither (decompress_info_ptr cinfo, int num_rows,
JSAMPIMAGE image_data, JSAMPARRAY output_workspace)
/* This version performs Floyd-Steinberg dithering */
{
#ifdef EIGHT_BIT_SAMPLES
register int c0, c1, c2;
int two_val;
#else
register FSERROR c0, c1, c2;
FSERROR two_val;
#endif
register FSERRPTR thisrowerr, nextrowerr;
JSAMPROW ptr0, ptr1, ptr2, outptr;
register LOCFSERROR cur0, cur1, cur2; /* current error or pixel value */
LOCFSERROR belowerr0, belowerr1, belowerr2; /* error for pixel below cur */
LOCFSERROR bpreverr0, bpreverr1, bpreverr2; /* error for below/prev col */
register FSERRPTR errorptr; /* => fserrors[] at column before current */
JSAMPROW ptr0, ptr1, ptr2; /* => current input pixel */
JSAMPROW outptr; /* => current output pixel */
histptr cachep;
register int pixcode;
int dir;
int dir; /* +1 or -1 depending on direction */
int dir3; /* 3*dir, for advancing errorptr */
int row;
long col;
long width = cinfo->image_width;
@@ -942,85 +942,111 @@ pass2_dither (decompress_info_ptr cinfo, int num_rows,
outptr = output_workspace[row];
if (on_odd_row) {
/* work right to left in this row */
ptr0 += width - 1;
ptr0 += width - 1; /* so point to rightmost pixel */
ptr1 += width - 1;
ptr2 += width - 1;
outptr += width - 1;
dir = -1;
thisrowerr = oddrowerrs + 3;
nextrowerr = evenrowerrs + width*3;
dir3 = -3;
errorptr = fserrors + (width+1)*3; /* point to entry after last column */
on_odd_row = FALSE; /* flip for next time */
} else {
/* work left to right in this row */
dir = 1;
thisrowerr = evenrowerrs + 3;
nextrowerr = oddrowerrs + width*3;
dir3 = 3;
errorptr = fserrors; /* point to entry before first real column */
on_odd_row = TRUE; /* flip for next time */
}
/* need only initialize this one entry in nextrowerr */
nextrowerr[0] = nextrowerr[1] = nextrowerr[2] = 0;
/* Preset error values: no error propagated to first pixel from left */
cur0 = cur1 = cur2 = 0;
/* and no error propagated to row below yet */
belowerr0 = belowerr1 = belowerr2 = 0;
bpreverr0 = bpreverr1 = bpreverr2 = 0;
for (col = width; col > 0; col--) {
/* For each component, get accumulated error and round to integer;
* form pixel value + error, and range-limit to 0..MAXJSAMPLE.
/* curN holds the error propagated from the previous pixel on the
* current line. Add the error propagated from the previous line
* to form the complete error correction term for this pixel, and
* round the error term (which is expressed * 16) to an integer.
* RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
* for either sign of the error value. Max error is +- MAXJSAMPLE.
* for either sign of the error value.
* Note: errorptr points to *previous* column's array entry.
*/
c0 = RIGHT_SHIFT(thisrowerr[0] + 8, 4);
c1 = RIGHT_SHIFT(thisrowerr[1] + 8, 4);
c2 = RIGHT_SHIFT(thisrowerr[2] + 8, 4);
c0 += GETJSAMPLE(*ptr0);
c1 += GETJSAMPLE(*ptr1);
c2 += GETJSAMPLE(*ptr2);
c0 = GETJSAMPLE(range_limit[c0]);
c1 = GETJSAMPLE(range_limit[c1]);
c2 = GETJSAMPLE(range_limit[c2]);
cur0 = RIGHT_SHIFT(cur0 + errorptr[dir3+0] + 8, 4);
cur1 = RIGHT_SHIFT(cur1 + errorptr[dir3+1] + 8, 4);
cur2 = RIGHT_SHIFT(cur2 + errorptr[dir3+2] + 8, 4);
/* Form pixel value + error, and range-limit to 0..MAXJSAMPLE.
* The maximum error is +- MAXJSAMPLE; this sets the required size
* of the range_limit array.
*/
cur0 += GETJSAMPLE(*ptr0);
cur1 += GETJSAMPLE(*ptr1);
cur2 += GETJSAMPLE(*ptr2);
cur0 = GETJSAMPLE(range_limit[cur0]);
cur1 = GETJSAMPLE(range_limit[cur1]);
cur2 = GETJSAMPLE(range_limit[cur2]);
/* Index into the cache with adjusted pixel value */
cachep = & histogram[c0 >> Y_SHIFT][c1 >> C_SHIFT][c2 >> C_SHIFT];
cachep = & histogram[cur0 >> Y_SHIFT][cur1 >> C_SHIFT][cur2 >> C_SHIFT];
/* If we have not seen this color before, find nearest colormap */
/* entry and update the cache */
if (*cachep == 0)
fill_inverse_cmap(cinfo, c0 >> Y_SHIFT, c1 >> C_SHIFT, c2 >> C_SHIFT);
fill_inverse_cmap(cinfo, cur0>>Y_SHIFT, cur1>>C_SHIFT, cur2>>C_SHIFT);
/* Now emit the colormap index for this cell */
pixcode = *cachep - 1;
*outptr = (JSAMPLE) pixcode;
/* Compute representation error for this pixel */
c0 -= GETJSAMPLE(colormap0[pixcode]);
c1 -= GETJSAMPLE(colormap1[pixcode]);
c2 -= GETJSAMPLE(colormap2[pixcode]);
/* Propagate error to adjacent pixels */
/* Remember that nextrowerr entries are in reverse order! */
two_val = c0 * 2;
nextrowerr[0-3] = c0; /* not +=, since not initialized yet */
c0 += two_val; /* form error * 3 */
nextrowerr[0+3] += c0;
c0 += two_val; /* form error * 5 */
nextrowerr[0 ] += c0;
c0 += two_val; /* form error * 7 */
thisrowerr[0+3] += c0;
two_val = c1 * 2;
nextrowerr[1-3] = c1; /* not +=, since not initialized yet */
c1 += two_val; /* form error * 3 */
nextrowerr[1+3] += c1;
c1 += two_val; /* form error * 5 */
nextrowerr[1 ] += c1;
c1 += two_val; /* form error * 7 */
thisrowerr[1+3] += c1;
two_val = c2 * 2;
nextrowerr[2-3] = c2; /* not +=, since not initialized yet */
c2 += two_val; /* form error * 3 */
nextrowerr[2+3] += c2;
c2 += two_val; /* form error * 5 */
nextrowerr[2 ] += c2;
c2 += two_val; /* form error * 7 */
thisrowerr[2+3] += c2;
/* Advance to next column */
ptr0 += dir;
{ register int pixcode = *cachep - 1;
*outptr = (JSAMPLE) pixcode;
/* Compute representation error for this pixel */
cur0 -= GETJSAMPLE(colormap0[pixcode]);
cur1 -= GETJSAMPLE(colormap1[pixcode]);
cur2 -= GETJSAMPLE(colormap2[pixcode]);
}
/* Compute error fractions to be propagated to adjacent pixels.
* Add these into the running sums, and simultaneously shift the
* next-line error sums left by 1 column.
*/
{ register LOCFSERROR bnexterr, delta;
bnexterr = cur0; /* Process component 0 */
delta = cur0 * 2;
cur0 += delta; /* form error * 3 */
errorptr[0] = (FSERROR) (bpreverr0 + cur0);
cur0 += delta; /* form error * 5 */
bpreverr0 = belowerr0 + cur0;
belowerr0 = bnexterr;
cur0 += delta; /* form error * 7 */
bnexterr = cur1; /* Process component 1 */
delta = cur1 * 2;
cur1 += delta; /* form error * 3 */
errorptr[1] = (FSERROR) (bpreverr1 + cur1);
cur1 += delta; /* form error * 5 */
bpreverr1 = belowerr1 + cur1;
belowerr1 = bnexterr;
cur1 += delta; /* form error * 7 */
bnexterr = cur2; /* Process component 2 */
delta = cur2 * 2;
cur2 += delta; /* form error * 3 */
errorptr[2] = (FSERROR) (bpreverr2 + cur2);
cur2 += delta; /* form error * 5 */
bpreverr2 = belowerr2 + cur2;
belowerr2 = bnexterr;
cur2 += delta; /* form error * 7 */
}
/* At this point curN contains the 7/16 error value to be propagated
* to the next pixel on the current line, and all the errors for the
* next line have been shifted over. We are therefore ready to move on.
*/
ptr0 += dir; /* Advance pixel pointers to next column */
ptr1 += dir;
ptr2 += dir;
outptr += dir;
thisrowerr += 3; /* cur-row error ptr advances to right */
nextrowerr -= 3; /* next-row error ptr advances to left */
errorptr += dir3; /* advance errorptr to current column */
}
/* Post-loop cleanup: we must unload the final error values into the
* final fserrors[] entry. Note we need not unload belowerrN because
* it is for the dummy column before or after the actual array.
*/
errorptr[0] = (FSERROR) bpreverr0; /* unload prev errs into array */
errorptr[1] = (FSERROR) bpreverr1;
errorptr[2] = (FSERROR) bpreverr2;
}
/* Emit converted rows to the output file */
(*cinfo->methods->put_pixel_rows) (cinfo, num_rows, &output_workspace);
@@ -1067,12 +1093,12 @@ color_quant_init (decompress_info_ptr cinfo)
/* Allocate Floyd-Steinberg workspace if necessary */
/* This isn't needed until pass 2, but again it is FAR storage. */
if (cinfo->use_dithering) {
size_t arraysize = (size_t) ((cinfo->image_width + 2L) * 3L * SIZEOF(FSERROR));
size_t arraysize = (size_t) ((cinfo->image_width + 2L) *
(3 * SIZEOF(FSERROR)));
evenrowerrs = (FSERRPTR) (*cinfo->emethods->alloc_medium) (arraysize);
oddrowerrs = (FSERRPTR) (*cinfo->emethods->alloc_medium) (arraysize);
/* we only need to zero the forward contribution for current row. */
jzero_far((void FAR *) evenrowerrs, arraysize);
fserrors = (FSERRPTR) (*cinfo->emethods->alloc_medium) (arraysize);
/* Initialize the propagated errors to zero. */
jzero_far((void FAR *) fserrors, arraysize);
on_odd_row = FALSE;
}
@@ -1157,6 +1183,14 @@ jsel2quantize (decompress_info_ptr cinfo)
cinfo->methods->color_quant_doit = color_quant_doit;
cinfo->methods->color_quant_term = color_quant_term;
cinfo->methods->color_quantize = color_quantize;
/* Quantized grayscale output is normally done by jquant1.c (which will do
* a much better job of it). But if the program is configured with only
* 2-pass quantization, then I have to do the job. In this situation,
* jseldcolor's clearing of the Cb/Cr component_needed flags is incorrect,
* because I will look at those components before conversion.
*/
cinfo->cur_comp_info[1]->component_needed = TRUE;
cinfo->cur_comp_info[2]->component_needed = TRUE;
}
}