Alien-FreeImage
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src/Source/LibPNG/pngwutil.c view on Meta::CPAN
}
default:
{
png_bytep sp;
png_bytep dp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
png_size_t pixel_bytes;
/* Start at the beginning */
dp = row;
/* Find out how many bytes each pixel takes up */
pixel_bytes = (row_info->pixel_depth >> 3);
/* Loop through the row, only looking at the pixels that matter */
for (i = png_pass_start[pass]; i < row_width;
i += png_pass_inc[pass])
{
/* Find out where the original pixel is */
sp = row + (png_size_t)i * pixel_bytes;
/* Move the pixel */
if (dp != sp)
memcpy(dp, sp, pixel_bytes);
/* Next pixel */
dp += pixel_bytes;
}
break;
}
}
/* Set new row width */
row_info->width = (row_info->width +
png_pass_inc[pass] - 1 -
png_pass_start[pass]) /
png_pass_inc[pass];
row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
row_info->width);
}
}
#endif
/* This filters the row, chooses which filter to use, if it has not already
* been specified by the application, and then writes the row out with the
* chosen filter.
*/
static void
png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
png_size_t row_bytes);
#define PNG_MAXSUM (((png_uint_32)(-1)) >> 1)
#define PNG_HISHIFT 10
#define PNG_LOMASK ((png_uint_32)0xffffL)
#define PNG_HIMASK ((png_uint_32)(~PNG_LOMASK >> PNG_HISHIFT))
void /* PRIVATE */
png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
{
png_bytep best_row;
#ifdef PNG_WRITE_FILTER_SUPPORTED
png_bytep prev_row, row_buf;
png_uint_32 mins, bpp;
png_byte filter_to_do = png_ptr->do_filter;
png_size_t row_bytes = row_info->rowbytes;
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
int num_p_filters = png_ptr->num_prev_filters;
#endif
png_debug(1, "in png_write_find_filter");
#ifndef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
if (png_ptr->row_number == 0 && filter_to_do == PNG_ALL_FILTERS)
{
/* These will never be selected so we need not test them. */
filter_to_do &= ~(PNG_FILTER_UP | PNG_FILTER_PAETH);
}
#endif
/* Find out how many bytes offset each pixel is */
bpp = (row_info->pixel_depth + 7) >> 3;
prev_row = png_ptr->prev_row;
#endif
best_row = png_ptr->row_buf;
#ifdef PNG_WRITE_FILTER_SUPPORTED
row_buf = best_row;
mins = PNG_MAXSUM;
/* The prediction method we use is to find which method provides the
* smallest value when summing the absolute values of the distances
* from zero, using anything >= 128 as negative numbers. This is known
* as the "minimum sum of absolute differences" heuristic. Other
* heuristics are the "weighted minimum sum of absolute differences"
* (experimental and can in theory improve compression), and the "zlib
* predictive" method (not implemented yet), which does test compressions
* of lines using different filter methods, and then chooses the
* (series of) filter(s) that give minimum compressed data size (VERY
* computationally expensive).
*
* GRR 980525: consider also
*
* (1) minimum sum of absolute differences from running average (i.e.,
* keep running sum of non-absolute differences & count of bytes)
* [track dispersion, too? restart average if dispersion too large?]
*
* (1b) minimum sum of absolute differences from sliding average, probably
* with window size <= deflate window (usually 32K)
*
* (2) minimum sum of squared differences from zero or running average
* (i.e., ~ root-mean-square approach)
*/
/* We don't need to test the 'no filter' case if this is the only filter
* that has been chosen, as it doesn't actually do anything to the data.
*/
if ((filter_to_do & PNG_FILTER_NONE) != 0 && filter_to_do != PNG_FILTER_NONE)
{
png_bytep rp;
png_uint_32 sum = 0;
png_size_t i;
int v;
for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
{
v = *rp;
sum += (v < 128) ? v : 256 - v;
}
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
{
png_uint_32 sumhi, sumlo;
int j;
sumlo = sum & PNG_LOMASK;
sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK; /* Gives us some footroom */
/* Reduce the sum if we match any of the previous rows */
for (j = 0; j < num_p_filters; j++)
{
if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
{
sumlo = (sumlo * png_ptr->filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
sumhi = (sumhi * png_ptr->filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
}
}
/* Factor in the cost of this filter (this is here for completeness,
* but it makes no sense to have a "cost" for the NONE filter, as
* it has the minimum possible computational cost - none).
*/
sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
PNG_COST_SHIFT;
sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
PNG_COST_SHIFT;
if (sumhi > PNG_HIMASK)
sum = PNG_MAXSUM;
else
sum = (sumhi << PNG_HISHIFT) + sumlo;
}
#endif
mins = sum;
}
/* Sub filter */
if (filter_to_do == PNG_FILTER_SUB)
/* It's the only filter so no testing is needed */
{
png_bytep rp, lp, dp;
png_size_t i;
for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
i++, rp++, dp++)
{
*dp = *rp;
}
for (lp = row_buf + 1; i < row_bytes;
i++, rp++, lp++, dp++)
{
*dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
}
best_row = png_ptr->sub_row;
}
else if ((filter_to_do & PNG_FILTER_SUB) != 0)
{
png_bytep rp, dp, lp;
png_uint_32 sum = 0, lmins = mins;
png_size_t i;
int v;
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
/* We temporarily increase the "minimum sum" by the factor we
* would reduce the sum of this filter, so that we can do the
* early exit comparison without scaling the sum each time.
*/
if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
{
int j;
png_uint_32 lmhi, lmlo;
lmlo = lmins & PNG_LOMASK;
lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
for (j = 0; j < num_p_filters; j++)
{
if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
{
lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
}
}
lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
PNG_COST_SHIFT;
lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
PNG_COST_SHIFT;
if (lmhi > PNG_HIMASK)
lmins = PNG_MAXSUM;
else
lmins = (lmhi << PNG_HISHIFT) + lmlo;
}
#endif
for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
i++, rp++, dp++)
{
v = *dp = *rp;
sum += (v < 128) ? v : 256 - v;
}
for (lp = row_buf + 1; i < row_bytes;
i++, rp++, lp++, dp++)
{
v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
sum += (v < 128) ? v : 256 - v;
if (sum > lmins) /* We are already worse, don't continue. */
break;
}
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
{
int j;
png_uint_32 sumhi, sumlo;
sumlo = sum & PNG_LOMASK;
sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
for (j = 0; j < num_p_filters; j++)
{
if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
{
sumlo = (sumlo * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
sumhi = (sumhi * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
}
}
sumlo = (sumlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
PNG_COST_SHIFT;
sumhi = (sumhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
PNG_COST_SHIFT;
if (sumhi > PNG_HIMASK)
sum = PNG_MAXSUM;
else
sum = (sumhi << PNG_HISHIFT) + sumlo;
}
#endif
if (sum < mins)
{
mins = sum;
best_row = png_ptr->sub_row;
}
}
/* Up filter */
if (filter_to_do == PNG_FILTER_UP)
{
png_bytep rp, dp, pp;
png_size_t i;
for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
pp = prev_row + 1; i < row_bytes;
i++, rp++, pp++, dp++)
{
*dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
}
best_row = png_ptr->up_row;
}
else if ((filter_to_do & PNG_FILTER_UP) != 0)
{
png_bytep rp, dp, pp;
png_uint_32 sum = 0, lmins = mins;
png_size_t i;
int v;
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
{
int j;
png_uint_32 lmhi, lmlo;
lmlo = lmins & PNG_LOMASK;
lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
for (j = 0; j < num_p_filters; j++)
{
if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
{
lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
}
}
lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
PNG_COST_SHIFT;
lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
PNG_COST_SHIFT;
if (lmhi > PNG_HIMASK)
lmins = PNG_MAXSUM;
else
lmins = (lmhi << PNG_HISHIFT) + lmlo;
}
#endif
for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
pp = prev_row + 1; i < row_bytes; i++)
{
v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
sum += (v < 128) ? v : 256 - v;
if (sum > lmins) /* We are already worse, don't continue. */
break;
}
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
{
int j;
png_uint_32 sumhi, sumlo;
sumlo = sum & PNG_LOMASK;
sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
for (j = 0; j < num_p_filters; j++)
{
if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
{
sumlo = (sumlo * png_ptr->filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
sumhi = (sumhi * png_ptr->filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
}
}
sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
PNG_COST_SHIFT;
sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
PNG_COST_SHIFT;
if (sumhi > PNG_HIMASK)
sum = PNG_MAXSUM;
else
sum = (sumhi << PNG_HISHIFT) + sumlo;
}
#endif
if (sum < mins)
{
mins = sum;
best_row = png_ptr->up_row;
}
}
/* Avg filter */
if (filter_to_do == PNG_FILTER_AVG)
{
png_bytep rp, dp, pp, lp;
png_uint_32 i;
for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
pp = prev_row + 1; i < bpp; i++)
{
*dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
}
for (lp = row_buf + 1; i < row_bytes; i++)
{
*dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
& 0xff);
}
best_row = png_ptr->avg_row;
}
else if ((filter_to_do & PNG_FILTER_AVG) != 0)
{
png_bytep rp, dp, pp, lp;
png_uint_32 sum = 0, lmins = mins;
png_size_t i;
int v;
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
{
int j;
png_uint_32 lmhi, lmlo;
lmlo = lmins & PNG_LOMASK;
lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
for (j = 0; j < num_p_filters; j++)
{
if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_AVG)
{
lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
}
}
lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
PNG_COST_SHIFT;
lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
PNG_COST_SHIFT;
if (lmhi > PNG_HIMASK)
lmins = PNG_MAXSUM;
else
lmins = (lmhi << PNG_HISHIFT) + lmlo;
}
#endif
for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
pp = prev_row + 1; i < bpp; i++)
{
v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
sum += (v < 128) ? v : 256 - v;
}
for (lp = row_buf + 1; i < row_bytes; i++)
{
v = *dp++ =
(png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2)) & 0xff);
sum += (v < 128) ? v : 256 - v;
if (sum > lmins) /* We are already worse, don't continue. */
break;
}
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
{
int j;
png_uint_32 sumhi, sumlo;
sumlo = sum & PNG_LOMASK;
sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
for (j = 0; j < num_p_filters; j++)
{
if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
{
sumlo = (sumlo * png_ptr->filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
sumhi = (sumhi * png_ptr->filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
}
}
sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
PNG_COST_SHIFT;
sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
PNG_COST_SHIFT;
if (sumhi > PNG_HIMASK)
sum = PNG_MAXSUM;
else
sum = (sumhi << PNG_HISHIFT) + sumlo;
}
#endif
if (sum < mins)
{
mins = sum;
best_row = png_ptr->avg_row;
}
}
/* Paeth filter */
if ((filter_to_do == PNG_FILTER_PAETH) != 0)
{
png_bytep rp, dp, pp, cp, lp;
png_size_t i;
for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
pp = prev_row + 1; i < bpp; i++)
{
*dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
}
for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
{
int a, b, c, pa, pb, pc, p;
b = *pp++;
c = *cp++;
a = *lp++;
p = b - c;
pc = a - c;
#ifdef PNG_USE_ABS
pa = abs(p);
pb = abs(pc);
pc = abs(p + pc);
#else
pa = p < 0 ? -p : p;
pb = pc < 0 ? -pc : pc;
pc = (p + pc) < 0 ? -(p + pc) : p + pc;
#endif
p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
*dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
}
best_row = png_ptr->paeth_row;
}
else if ((filter_to_do & PNG_FILTER_PAETH) != 0)
{
png_bytep rp, dp, pp, cp, lp;
png_uint_32 sum = 0, lmins = mins;
png_size_t i;
int v;
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
{
int j;
png_uint_32 lmhi, lmlo;
lmlo = lmins & PNG_LOMASK;
lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
for (j = 0; j < num_p_filters; j++)
{
if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
{
lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
}
}
lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
PNG_COST_SHIFT;
lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
PNG_COST_SHIFT;
if (lmhi > PNG_HIMASK)
lmins = PNG_MAXSUM;
else
lmins = (lmhi << PNG_HISHIFT) + lmlo;
}
#endif
for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
pp = prev_row + 1; i < bpp; i++)
{
v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
sum += (v < 128) ? v : 256 - v;
}
for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
{
int a, b, c, pa, pb, pc, p;
b = *pp++;
c = *cp++;
a = *lp++;
#ifndef PNG_SLOW_PAETH
src/Source/LibPNG/pngwutil.c view on Meta::CPAN
#else /* SLOW_PAETH */
p = a + b - c;
pa = abs(p - a);
pb = abs(p - b);
pc = abs(p - c);
if (pa <= pb && pa <= pc)
p = a;
else if (pb <= pc)
p = b;
else
p = c;
#endif /* SLOW_PAETH */
v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
sum += (v < 128) ? v : 256 - v;
if (sum > lmins) /* We are already worse, don't continue. */
break;
}
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
{
int j;
png_uint_32 sumhi, sumlo;
sumlo = sum & PNG_LOMASK;
sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
for (j = 0; j < num_p_filters; j++)
{
if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
{
sumlo = (sumlo * png_ptr->filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
sumhi = (sumhi * png_ptr->filter_weights[j]) >>
PNG_WEIGHT_SHIFT;
}
}
sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
PNG_COST_SHIFT;
sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
PNG_COST_SHIFT;
if (sumhi > PNG_HIMASK)
sum = PNG_MAXSUM;
else
sum = (sumhi << PNG_HISHIFT) + sumlo;
}
#endif
if (sum < mins)
{
best_row = png_ptr->paeth_row;
}
}
#endif /* WRITE_FILTER */
/* Do the actual writing of the filtered row data from the chosen filter. */
png_write_filtered_row(png_ptr, best_row, row_info->rowbytes+1);
#ifdef PNG_WRITE_FILTER_SUPPORTED
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
/* Save the type of filter we picked this time for future calculations */
if (png_ptr->num_prev_filters > 0)
{
int j;
for (j = 1; j < num_p_filters; j++)
{
png_ptr->prev_filters[j] = png_ptr->prev_filters[j - 1];
}
png_ptr->prev_filters[j] = best_row[0];
}
#endif
#endif /* WRITE_FILTER */
}
/* Do the actual writing of a previously filtered row. */
static void
png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
png_size_t full_row_length/*includes filter byte*/)
{
png_debug(1, "in png_write_filtered_row");
png_debug1(2, "filter = %d", filtered_row[0]);
png_compress_IDAT(png_ptr, filtered_row, full_row_length, Z_NO_FLUSH);
/* Swap the current and previous rows */
if (png_ptr->prev_row != NULL)
{
png_bytep tptr;
tptr = png_ptr->prev_row;
png_ptr->prev_row = png_ptr->row_buf;
png_ptr->row_buf = tptr;
}
/* Finish row - updates counters and flushes zlib if last row */
png_write_finish_row(png_ptr);
#ifdef PNG_WRITE_FLUSH_SUPPORTED
png_ptr->flush_rows++;
if (png_ptr->flush_dist > 0 &&
png_ptr->flush_rows >= png_ptr->flush_dist)
{
png_write_flush(png_ptr);
}
#endif /* WRITE_FLUSH */
}
#endif /* WRITE */
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