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Bug 592628: Scale Image adds asymmetric artifacts to image edges

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second problem described, regarding the perceived shift.

NPOT sized symmetric images downscaled by a ratio greater
than 2 (src:dst > 2:1), still lose the symmetry. It is a
consequence of the intermediate halving step which is top
left aligned.
This commit is contained in:
Massimo Valentini 2012-10-13 14:56:47 +02:00
parent e09233f080
commit f9387909f3
1 changed files with 26 additions and 16 deletions
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42
app/paint-funcs/scale-region.c
View file

@ -62,7 +62,9 @@ static void scale (TileManager *srcTM,
GimpProgressFunc progress_callback,
gpointer progress_data,
gint *progress,
gint max_progress);
gint max_progress,
const gdouble scalex,
const gdouble scaley);
static void decimate_xy (TileManager *srcTM,
TileManager *dstTM,
GimpInterpolationType interpolation,
@ -212,14 +214,14 @@ scale_determine_levels (PixelRegion *srcPR,
while (scalex < 0.5 && width > 1)
{
scalex *= 2;
width /= 2;
width = (width + 1) / 2;
*levelx += 1;
}
while (scaley < 0.5 && height > 1)
{
scaley *= 2;
height *= 2;
height = (height + 1) / 2;
*levely += 1;
}
}
@ -242,8 +244,8 @@ scale_determine_progress (PixelRegion *srcPR,
while (levelx > 0 && levely > 0)
{
width >>= 1;
height >>= 1;
width = (width + 1) >> 1;
height = (height + 1) >> 1;
levelx--;
levely--;
@ -252,7 +254,7 @@ scale_determine_progress (PixelRegion *srcPR,
while (levelx > 0)
{
width >>= 1;
width = (width + 1) >> 1;
levelx--;
tiles += NUM_TILES (width, height);
@ -260,7 +262,7 @@ scale_determine_progress (PixelRegion *srcPR,
while (levely > 0)
{
height >>= 1;
height = (height + 1) >> 1;
levely--;
tiles += NUM_TILES (width, height);
@ -288,6 +290,8 @@ scale_region_tile (PixelRegion *srcPR,
gint progress = 0;
gint levelx = 0;
gint levely = 0;
gdouble scalex = (gdouble) width / dstPR->w;
gdouble scaley = (gdouble) height / dstPR->h;
/* determine scaling levels */
if (interpolation != GIMP_INTERPOLATION_NONE)
@ -300,13 +304,16 @@ scale_region_tile (PixelRegion *srcPR,
if (levelx == 0 && levely == 0)
{
scale (srcTM, dstTM, interpolation,
progress_callback, progress_data, &progress, max_progress);
progress_callback, progress_data, &progress, max_progress,
scalex, scaley);
}
while (levelx > 0 && levely > 0)
{
width >>= 1;
height >>= 1;
width = (width + 1) >> 1;
height = (height + 1) >> 1;
scalex *= .5;
scaley *= .5;
tmpTM = tile_manager_new (width, height, bytes);
decimate_xy (srcTM, tmpTM, interpolation,
@ -322,7 +329,8 @@ scale_region_tile (PixelRegion *srcPR,
while (levelx > 0)
{
width >>= 1;
width = (width + 1) >> 1;
scalex *= .5;
tmpTM = tile_manager_new (width, height, bytes);
decimate_x (srcTM, tmpTM, interpolation,
@ -337,7 +345,8 @@ scale_region_tile (PixelRegion *srcPR,
while (levely > 0)
{
height >>= 1;
height = (height + 1) >> 1;
scaley *= .5;
tmpTM = tile_manager_new (width, height, bytes);
decimate_y (srcTM, tmpTM, interpolation,
@ -353,7 +362,8 @@ scale_region_tile (PixelRegion *srcPR,
if (tmpTM != NULL)
{
scale (tmpTM, dstTM, interpolation,
progress_callback, progress_data, &progress, max_progress);
progress_callback, progress_data, &progress, max_progress,
scalex, scaley);
tile_manager_unref (tmpTM);
}
@ -370,7 +380,9 @@ scale (TileManager *srcTM,
GimpProgressFunc progress_callback,
gpointer progress_data,
gint *progress,
gint max_progress)
gint max_progress,
const gdouble scalex,
const gdouble scaley)
{
PixelRegion region;
PixelSurround *surround = NULL;
@ -379,8 +391,6 @@ scale (TileManager *srcTM,
const guint bytes = tile_manager_bpp (dstTM);
const guint dst_width = tile_manager_width (dstTM);
const guint dst_height = tile_manager_height (dstTM);
const gdouble scaley = (gdouble) src_height / (gdouble) dst_height;
const gdouble scalex = (gdouble) src_width / (gdouble) dst_width;
gpointer pr;
gfloat *kernel_lookup = NULL;