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Mostly rewritten to improve accuracy. Fixes bug #104693.

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2003-04-27  Pedro Gimeno  <pggimeno@wanadoo.es>

	* app/paint-funcs/paint-funcs.c (shrink_line): Mostly rewritten to
	improve accuracy. Fixes bug #104693.
This commit is contained in:
Pedro Gimeno 2003-04-27 18:58:56 +00:00 committed by Pedro Gimeno Fortea
parent 67e5f1d157
commit c8ecdeec5c
2 changed files with 46 additions and 44 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2003-04-27 Pedro Gimeno <pggimeno@wanadoo.es>
* app/paint-funcs/paint-funcs.c (shrink_line): Mostly rewritten to
improve accuracy. Fixes bug #104693.
2003-04-25 Pedro Gimeno <pggimeno@wanadoo.es>
* app/paint-funcs/paint-funcs.c: Some reformattings to improve

85
app/paint-funcs/paint-funcs.c
View File

@ -2864,19 +2864,19 @@ shrink_line (gdouble *dest,
gint width,
GimpInterpolationType interp)
{
gint x, b;
gdouble *source, *destp;
register gdouble accum;
register guint max;
register gdouble mant, tmp;
register const gdouble step = old_width / (gdouble) width;
register const gdouble inv_step = 1.0 / step;
gdouble position;
gint x;
gint b;
gdouble *srcp;
gdouble *destp;
gdouble accum;
gdouble slice;
const gdouble avg_ratio = (gdouble) width / old_width;
gint srcpos;
#if 0
g_printerr ("shrink_line bytes=%d old_width=%d width=%d interp=%d "
"step=%f inv_step=%f\n",
bytes, old_width, width, interp, step, inv_step);
"avg_ratio=%f\n",
bytes, old_width, width, interp, avg_ratio);
#endif
@ -2884,52 +2884,49 @@ shrink_line (gdouble *dest,
{
/* This algorithm calculates the weighted average of pixel data that
each output pixel must receive, taking into account that it always
scales down, i.e. there are more than one input pixels per each
scales down, i.e. there's always more than one input pixel per each
output pixel.
source and destp are the data pointers, position is the index to
the split point, mant is the partial pixel data, tmp is where the
output value is calculated, accum is used to accumulate only whole
pixels, max is the number of whole pixels (if any).
*/
/* Both input and output data are interleaved. Calculate the pointer
to each. */
source = &src[b];
srcp = &src[b];
destp = &dest[b];
position = -1;
srcpos = 0;
/* Load the first partial pixel data with one whole input pixel. */
mant = *source;
/* Initialize accum to the first pixel slice. As there is no partial
pixel at start, that value is 0. */
accum = 0.0;
for (x = 0; x < width; x++)
{
source += bytes;
accum = 0;
max = (int) (position + step) - (int) position;
max--;
/* Get all possible whole pixels. */
while (max)
/* Accumulate whole pixels. */
while (srcpos < old_width)
{
accum += *source;
source += bytes;
max--;
accum += *srcp;
srcp += bytes;
srcpos += width;
}
tmp = accum + mant; /* Add up all the whole pixels and the
previous partial pixel. */
mant = (position + step) - (int) (position + step);
mant *= *source; /* Calculate the last partial pixel. */
srcpos -= old_width;
tmp += mant; /* Add the last chunk to final result. */
tmp *= inv_step; /* Scale the pixel down (average.) */
mant = *source - mant; /* Take the remaining pixel data. */
*destp = tmp; /* Store the final result. */
destp += bytes; /* Advance to the next output pixel. */
position += step; /* Advance to the next pixel position. */
/* We've accumulated a whole pixel where just a slice of it was
needed. Subtract it now. */
slice = (srcpos == 0) ? 0.0 : (srcp[-bytes] * srcpos) / width;
accum -= slice;
*destp = accum * avg_ratio;
destp += bytes;
/* That slice is the initial value for the next round. */
accum = slice;
}
#if 0
/* Sanity check: srcp should point to the next-to-last position. */
if (!(srcp - src - b == old_width * bytes))
g_warning ("Assertion (srcp - src - b == old_width * bytes) failed.");
#endif
}
}
@ -3565,7 +3562,7 @@ fatten_region (PixelRegion *src,
{
max[x][0] = 0; /* buf[0][x] is always 0 */
max[x][1] = buf[1][x]; /* MAX (buf[1][x], max[x][0]) always = buf[1][x]*/
for (j = 2; j < yradius+1; j++)
for (j = 2; j < yradius + 1; j++)
max[x][j] = MAX(buf[j][x], max[x][j-1]);
}
@ -3942,7 +3939,7 @@ border_region (PixelRegion *src,
density[ x] += yradius;
density[-x] = density[x];
}
for (x = 0; x < (xradius+1); x++) /* compute density[][] */
for (x = 0; x < (xradius + 1); x++) /* compute density[][] */
{
register gdouble tmpx, tmpy, dist;
guchar a;