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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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141
jquant1.c
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@@ -1,7 +1,7 @@
/*
* jquant1.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.
*
@@ -81,37 +81,39 @@ static JSAMPARRAY input_buffer; /* color conversion workspace */
/* 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.
*
* In each of the xxxrowerrs[] arrays, indexing is [component#][position].
* 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 is indexed [component#][position].
* We provide (#columns + 2) entries per component; the extra entry at each
* end saves us from special-casing the first and last pixels.
* 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!
*
* 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[MAX_COMPONENTS]; /* errors for even rows */
static FSERRPTR oddrowerrs[MAX_COMPONENTS]; /* errors for odd rows */
static FSERRPTR fserrors[MAX_COMPONENTS]; /* accumulated errors */
static boolean on_odd_row; /* flag to remember which row we are on */
@@ -349,10 +351,9 @@ color_quant_init (decompress_info_ptr cinfo)
size_t arraysize = (size_t) ((cinfo->image_width + 2L) * SIZEOF(FSERROR));
for (i = 0; i < cinfo->color_out_comps; i++) {
evenrowerrs[i] = (FSERRPTR) (*cinfo->emethods->alloc_medium) (arraysize);
oddrowerrs[i] = (FSERRPTR) (*cinfo->emethods->alloc_medium) (arraysize);
/* we only need to zero the forward contribution for current row. */
jzero_far((void FAR *) evenrowerrs[i], arraysize);
fserrors[i] = (FSERRPTR) (*cinfo->emethods->alloc_medium) (arraysize);
/* Initialize the propagated errors to zero. */
jzero_far((void FAR *) fserrors[i], arraysize);
}
on_odd_row = FALSE;
}
@@ -426,6 +427,9 @@ color_quantize3 (decompress_info_ptr cinfo, int num_rows,
register JSAMPROW ptr0, ptr1, ptr2, ptrout;
register long col;
int row;
JSAMPROW colorindex0 = colorindex[0];
JSAMPROW colorindex1 = colorindex[1];
JSAMPROW colorindex2 = colorindex[2];
long width = cinfo->image_width;
for (row = 0; row < num_rows; row++) {
@@ -435,9 +439,9 @@ color_quantize3 (decompress_info_ptr cinfo, int num_rows,
ptr2 = input_buffer[2];
ptrout = output_data[row];
for (col = width; col > 0; col--) {
pixcode = GETJSAMPLE(colorindex[0][GETJSAMPLE(*ptr0++)]);
pixcode += GETJSAMPLE(colorindex[1][GETJSAMPLE(*ptr1++)]);
pixcode += GETJSAMPLE(colorindex[2][GETJSAMPLE(*ptr2++)]);
pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptr0++)]);
pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptr1++)]);
pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptr2++)]);
*ptrout++ = (JSAMPLE) pixcode;
}
}
@@ -449,21 +453,24 @@ color_quantize_dither (decompress_info_ptr cinfo, int num_rows,
JSAMPIMAGE input_data, JSAMPARRAY output_data)
/* General case, with Floyd-Steinberg dithering */
{
register FSERROR val;
FSERROR two_val;
register FSERRPTR thisrowerr, nextrowerr;
register LOCFSERROR cur; /* current error or pixel value */
LOCFSERROR belowerr; /* error for pixel below cur */
LOCFSERROR bpreverr; /* error for below/prev col */
LOCFSERROR bnexterr; /* error for below/next col */
LOCFSERROR delta;
register FSERRPTR errorptr; /* => fserrors[] at column before current */
register JSAMPROW input_ptr;
register JSAMPROW output_ptr;
JSAMPLE *range_limit = cinfo->sample_range_limit;
JSAMPROW colorindex_ci;
JSAMPROW colormap_ci;
register int pixcode;
int pixcode;
int dir; /* 1 for left-to-right, -1 for right-to-left */
int ci;
int nc = cinfo->color_out_comps;
int row;
long col_counter;
long width = cinfo->image_width;
JSAMPLE *range_limit = cinfo->sample_range_limit;
SHIFT_TEMPS
for (row = 0; row < num_rows; row++) {
@@ -472,56 +479,74 @@ color_quantize_dither (decompress_info_ptr cinfo, int num_rows,
jzero_far((void FAR *) output_data[row],
(size_t) (width * SIZEOF(JSAMPLE)));
for (ci = 0; ci < nc; ci++) {
input_ptr = input_buffer[ci];
output_ptr = output_data[row];
if (on_odd_row) {
/* work right to left in this row */
input_ptr += width - 1; /* so point to rightmost pixel */
output_ptr += width - 1;
dir = -1;
input_ptr = input_buffer[ci] + (width-1);
output_ptr = output_data[row] + (width-1);
thisrowerr = oddrowerrs[ci] + 1;
nextrowerr = evenrowerrs[ci] + width;
errorptr = fserrors[ci] + (width+1); /* point to entry after last column */
} else {
/* work left to right in this row */
dir = 1;
input_ptr = input_buffer[ci];
output_ptr = output_data[row];
thisrowerr = evenrowerrs[ci] + 1;
nextrowerr = oddrowerrs[ci] + width;
errorptr = fserrors[ci]; /* point to entry before first real column */
}
colorindex_ci = colorindex[ci];
colormap_ci = colormap[ci];
*nextrowerr = 0; /* need only initialize this one entry */
/* Preset error values: no error propagated to first pixel from left */
cur = 0;
/* and no error propagated to row below yet */
belowerr = bpreverr = 0;
for (col_counter = width; col_counter > 0; col_counter--) {
/* Get accumulated error for this component, round to integer.
/* cur 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.
* Note: errorptr points to *previous* column's array entry.
*/
val = RIGHT_SHIFT(*thisrowerr + 8, 4);
/* Compute pixel value + error compensation, range-limit to
* 0..MAXJSAMPLE. Note max error value is +- MAXJSAMPLE.
cur = RIGHT_SHIFT(cur + errorptr[dir] + 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.
*/
val = GETJSAMPLE(range_limit[GETJSAMPLE(*input_ptr) + val]);
cur += GETJSAMPLE(*input_ptr);
cur = GETJSAMPLE(range_limit[cur]);
/* Select output value, accumulate into output code for this pixel */
pixcode = GETJSAMPLE(*output_ptr) + GETJSAMPLE(colorindex_ci[val]);
*output_ptr = (JSAMPLE) pixcode;
pixcode = GETJSAMPLE(colorindex_ci[cur]);
*output_ptr += (JSAMPLE) pixcode;
/* Compute actual representation error at this pixel */
/* Note: we can do this even though we don't yet have the final */
/* value of pixcode, because the colormap is orthogonal. */
val -= GETJSAMPLE(colormap_ci[pixcode]);
/* Propagate error to (same component of) adjacent pixels */
/* Remember that nextrowerr entries are in reverse order! */
two_val = val * 2;
nextrowerr[-1] = val; /* not +=, since not initialized yet */
val += two_val; /* form error * 3 */
nextrowerr[ 1] += val;
val += two_val; /* form error * 5 */
nextrowerr[ 0] += val;
val += two_val; /* form error * 7 */
thisrowerr[ 1] += val;
/* Note: we can do this even though we don't have the final */
/* pixel code, because the colormap is orthogonal. */
cur -= GETJSAMPLE(colormap_ci[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.
*/
bnexterr = cur;
delta = cur * 2;
cur += delta; /* form error * 3 */
errorptr[0] = (FSERROR) (bpreverr + cur);
cur += delta; /* form error * 5 */
bpreverr = belowerr + cur;
belowerr = bnexterr;
cur += delta; /* form error * 7 */
/* At this point cur 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.
*/
input_ptr += dir; /* advance input ptr to next column */
output_ptr += dir; /* advance output ptr to next column */
thisrowerr++; /* cur-row error ptr advances to right */
nextrowerr--; /* next-row error ptr advances to left */
errorptr += dir; /* advance errorptr to current column */
}
/* Post-loop cleanup: we must unload the final error value into the
* final fserrors[] entry. Note we need not unload belowerr because
* it is for the dummy column before or after the actual array.
*/
errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */
}
on_odd_row = (on_odd_row ? FALSE : TRUE);
}