diff --git a/plug-ins/pygimp/plug-ins/palette-sort.py b/plug-ins/pygimp/plug-ins/palette-sort.py
index 1d590d1..3d500ee 100644
--- a/plug-ins/pygimp/plug-ins/palette-sort.py
+++ b/plug-ins/pygimp/plug-ins/palette-sort.py
@@ -14,31 +14,281 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from gimpfu import *
+from colorsys import rgb_to_yiq
+from random import randint
 
 gettext.install("gimp20-python", gimp.locale_directory, unicode=True)
 
-def palette_sort (palette, model, channel, ascending):
+AVAILABLE_CHANNELS = (_("Red"), _("Green"), _("Blue"),
+                      _("Luma (Y)"),
+                      _("Hue"), _("Saturation"), _("Value"),
+                      _("Saturation (HSL)"), _("Lightness (HSL)"),
+                      _("Index"),
+                      _("Random"))
+
+GRAIN_SCALE = (1.0, 1.0 , 1.0,
+              1.0,
+              360., 100., 100.,
+              100., 100.,
+              100., 256., 256.,
+              256., 360.)
+
+SELECT_ALL = 0
+SELECT_SLICE = 1
+SELECT_AUTOSLICE = 2
+SELECT_PARTITIONED = 3
+SELECTIONS = (SELECT_ALL, SELECT_SLICE, SELECT_AUTOSLICE, SELECT_PARTITIONED)
+
+
+def noop(v, i):
+    return v
+
+
+def to_hsv(v, i):
+    return v.to_hsv()
+
+
+def to_hsl(v, i):
+    return v.to_hsl()
+
+
+def to_yiq(v, i):
+    return rgb_to_yiq(*v[:-1])
+
+
+def to_index(v, i):
+    return (i,)
+
+def to_random(v, i):
+    return (randint(0, 0x7fffffff),)
+
+
+channel_getters = [ (noop, 0), (noop, 1), (noop, 2),
+                    (to_yiq, 0),
+                    (to_hsv, 0), (to_hsv, 1), (to_hsv, 2),
+                    (to_hsl, 1), (to_hsl, 2),
+                    (to_index, 0),
+                    (to_random, 0)]
+
+
+try:
+    from colormath.color_objects import RGBColor, LabColor, LCHabColor
+    AVAILABLE_CHANNELS = AVAILABLE_CHANNELS + (_("Lightness (LAB)"), _("A-color"), _("B-color"),
+                                               _("Chroma (LCHab)"), _("Hue (LCHab)"))
+    to_lab = lambda v,i: RGBColor(*v[:-1]).convert_to('LAB').get_value_tuple()
+    to_lchab = lambda v,i: RGBColor(*v[:-1]).convert_to('LCHab').get_value_tuple()
+    channel_getters.extend([(to_lab, 0), (to_lab, 1), (to_lab, 2),
+                            (to_lchab, 1), (to_lchab, 2)])
+except ImportError:
+    pass
+
+
+def parse_slice(s, numcolors):
+    """Parse a slice spec and return (start, nrows, length)
+    All items are optional. Omitting them makes the largest possible selection that
+    exactly fits the other items.
+
+    start:nrows,length
+
+
+    '' selects all items, as does ':'
+    ':4,' makes a 4-row selection out of all colors (length auto-determined)
+    ':4' also.
+    ':1,4' selects the first 4 colors
+    ':,4' selects rows of 4 colors (nrows auto-determined)
+    ':4,4' selects 4 rows of 4 colors
+    '4:' selects a single row of all colors after 4, inclusive.
+    '4:,4' selects rows of 4 colors, starting at 4 (nrows auto-determined)
+    '4:4,4' selects 4 rows of 4 colors (16 colors total), beginning at index 4.
+    '4' is illegal (ambiguous)
+
+
+    In general, slices are comparable to a numpy sub-array.
+    'start at element START, with shape (NROWS, LENGTH)'
+
+    """
+    s = s.strip()
+
+    def notunderstood():
+        raise ValueError('Slice %r not understood. Should be in format'
+                         ' START?:NROWS?,ROWLENGTH? eg. "0:4,16".' % s)
+    def _int(v):
+        try:
+            return int(v)
+        except ValueError:
+            notunderstood()
+    if s in ('', ':', ':,'):
+        return 0, 1, numcolors # entire palette, one row
+    if s.count(':') != 1:
+        notunderstood()
+    rowpos = s.find(':')
+    start = 0
+    if rowpos > 0:
+        start = _int(s[:rowpos])
+    numcolors -= start
+    nrows = 1
+    if ',' in s:
+        commapos = s.find(',')
+        nrows = s[rowpos+1:commapos]
+        length = s[commapos+1:]
+        if not nrows:
+            if not length:
+                notunderstood()
+            else:
+                length = _int(length)
+                if length == 0:
+                    notunderstood()
+                nrows = numcolors // length
+                if numcolors % length:
+                    nrows = -nrows
+        elif not length:
+            nrows = _int(nrows)
+            if nrows == 0:
+                notunderstood()
+            length = numcolors // nrows
+            if numcolors % nrows:
+                length = -length
+        else:
+            nrows = _int(nrows)
+            if nrows == 0:
+                notunderstood()
+            length = _int(length)
+            if length == 0:
+                notunderstood()
+    else:
+        nrows = _int(s[rowpos+1:])
+        if nrows == 0:
+            notunderstood()
+        length = numcolors // nrows
+        if numcolors % nrows:
+            length = -length
+    return start, nrows, length
+
+
+def quantization_grain(channel, g):
+    "Given a channel and a quantization, return the size of a quantization grain"
+    g = max(1.0, g)
+    if g <= 1.0:
+        g = 0.00001
+    else:
+        g = max(0.00001, GRAIN_SCALE[channel] / g)
+    return g
+
+
+def palette_sort (palette, selection, slice_expr, channel, quantize,
+                  ascending, pchannel, pquantize):
+
+    grain = quantization_grain(channel, quantize)
+    pgrain = quantization_grain(pchannel, pquantize)
+
     #If palette is read only, work on a copy:
     editable = pdb.gimp_palette_is_editable(palette)
-    if not editable:palette = pdb.gimp_palette_duplicate (palette)
+    if not editable:
+        palette = pdb.gimp_palette_duplicate (palette)
 
     num_colors = pdb.gimp_palette_get_info (palette)
-    entry_list = []
-    for i in xrange (num_colors):
-        entry =  (pdb.gimp_palette_entry_get_name (palette, i),
-                  pdb.gimp_palette_entry_get_color (palette, i))
-        index = entry[1][channel]
-        if model == "HSV":
-            index = entry[1].to_hsv()[channel]
-        else:
-            index = entry[1][channel]
-        entry_list.append ((index, entry))
-    entry_list.sort(lambda x,y: cmp(x[0], y[0]))
-    if not ascending:
-        entry_list.reverse()
-    for i in xrange(num_colors):
-        pdb.gimp_palette_entry_set_name (palette, i, entry_list[i][1][0])
-        pdb.gimp_palette_entry_set_color (palette, i, entry_list[i][1][1])
+
+    start, nrows, length = None, None, None
+    if selection == SELECT_AUTOSLICE:
+        def find_index(color, startindex=0):
+            for i in range(startindex, num_colors):
+                c = pdb.gimp_palette_entry_get_color (palette, i)
+                if c == color:
+                    return i
+            return None
+        def hexcolor(c):
+            return "#%02x%02x%02x" % tuple(c[:-1])
+        fg = pdb.gimp_context_get_foreground()
+        bg = pdb.gimp_context_get_background()
+        start = find_index(fg)
+        end = find_index(bg)
+        if start is None:
+            raise ValueError("Couldn't find foreground color %r in palette" % list(fg))
+        if end is None:
+            raise ValueError("Couldn't find background color %r in palette" % list(bg))
+        if find_index(fg, start + 1):
+            raise ValueError('Autoslice cannot be used when more than one'
+                             ' instance of an endpoint'
+                             ' (%s) is present' % hexcolor(fg))
+        if find_index(bg, end + 1):
+            raise ValueError('Autoslice cannot be used when more than one'
+                             ' instance of an endpoint'
+                             ' (%s) is present' % hexcolor(bg))
+        if start > end:
+            end, start = start, end
+        length = (end - start) + 1
+        try:
+            _, nrows, _ = parse_slice(slice_expr, length)
+            nrows = abs(nrows)
+            if length % nrows:
+                raise ValueError('Total length %d not evenly divisible'
+                                 ' by number of rows %d' % (length, nrows))
+            length /= nrows
+        except ValueError:
+            # bad expression is okay here, just assume one row
+            nrows = 1
+        # remaining behaviour is implemented by SELECT_SLICE 'inheritance'.
+        selection= SELECT_SLICE
+    elif selection in (SELECT_SLICE, SELECT_PARTITIONED):
+        start, nrows, length = parse_slice(slice_expr, num_colors)
+
+    channels_getter, channel_index = channel_getters[channel]
+
+    def get_colors (start, end):
+        result = []
+        for i in range (start, end):
+            entry =  (pdb.gimp_palette_entry_get_name (palette, i),
+                      pdb.gimp_palette_entry_get_color (palette, i))
+            index = channels_getter(entry[1], i)[channel_index]
+            index = (index - (index % grain))
+            result.append((index, entry))
+        return result
+
+    if selection == SELECT_ALL:
+        entry_list = get_colors(0, num_colors)
+        entry_list.sort(key=lambda v:v[0], reverse=not ascending)
+        for i in range(num_colors):
+            pdb.gimp_palette_entry_set_name (palette, i, entry_list[i][1][0])
+            pdb.gimp_palette_entry_set_color (palette, i, entry_list[i][1][1])
+
+    elif selection == SELECT_PARTITIONED:
+        if num_colors < (start + length * nrows) - 1:
+            raise ValueError('Not enough entries in palette to sort complete rows!'
+                             ' got %d, expected >=%d' % (num_colors, start + length * nrows))
+        pchannels_getter, pchannel_index = channel_getters[pchannel]
+        for row in range(nrows):
+            partition_spans = [1]
+            rowstart = start + (row * length)
+            old_color = pdb.gimp_palette_entry_get_color (palette,
+                                                          rowstart)
+            old_partition = pchannels_getter(old_color, rowstart)[pchannel_index]
+            old_partition = old_partition - (old_partition % pgrain)
+            for i in range(rowstart + 1, rowstart + length):
+                this_color = pdb.gimp_palette_entry_get_color (palette, i)
+                this_partition = pchannels_getter(this_color, i)[pchannel_index]
+                this_partition = this_partition - (this_partition % pgrain)
+                if this_partition == old_partition:
+                    partition_spans[-1] += 1
+                else:
+                    partition_spans.append(1)
+                    old_partition = this_partition
+            base = rowstart
+            for size in partition_spans:
+                palette_sort(palette, SELECT_SLICE, '%d:1,%d' % (base, size),
+                             channel, quantize, ascending, 0, 1.0)
+                base += size
+    else:
+        stride = length
+        if num_colors < (start + stride * nrows) - 1:
+            raise ValueError('Not enough entries in palette to sort complete rows!'
+                             ' got %d, expected >=%d' % (num_colors, start + stride * nrows))
+
+        for row_start in range(start, start + stride * nrows, stride):
+            sublist = get_colors(row_start, row_start + stride)
+            sublist.sort(key=lambda v:v[0], reverse=not ascending)
+            for i, entry in zip(range(row_start, row_start + stride), sublist):
+                pdb.gimp_palette_entry_set_name (palette, i, entry[1][0])
+                pdb.gimp_palette_entry_set_color (palette, i, entry[1][1])
 
     return palette
 
@@ -46,22 +296,25 @@ def palette_sort (palette, model, channel, ascending):
 register(
     "python-fu-palette-sort",
     N_("Sort the colors in a palette"),
-    "palette_merge (palette, model, channel, ascending) -> new_palette",
-    "Joao S. O. Bueno Calligaris, Carol Spears",
+    "palette_sort (palette, selection, slice_expr, channel, quantize,"
+    " ascending, pchannel, pquantize) -> new_palette",
+    "Joao S. O. Bueno Calligaris, Carol Spears, David Gowers",
     "Joao S. O. Bueno Calligaris",
     "2006",
     N_("_Sort Palette..."),
     "",
     [
         (PF_PALETTE, "palette",  _("Palette"), ""),
-        (PF_RADIO,   "model",    _("Color _model"), "HSV",
-                                    ((_("RGB"), "RGB"),
-                                     (_("HSV"), "HSV"))),
-        (PF_RADIO,   "channel",  _("Channel to _sort"), 2,
-                                    ((_("Red or Hue"),          0),
-                                     (_("Green or Saturation"), 1),
-                                     (_("Blue or Value"),       2))),
-        (PF_BOOL,   "ascending", _("_Ascending"), True)
+        (PF_OPTION, "selections", _("Se_lections"), SELECT_ALL,
+                    (_("All"), _("Slice / Array"), _("Autoslice (fg->bg)"), _("Partitioned"))),
+        (PF_STRING,    "slice-expr", _("Slice _expression"), ''),
+        (PF_OPTION,   "channel",    _("Channel to _sort"), 3,
+                                    AVAILABLE_CHANNELS),
+        (PF_FLOAT,  "quantize", _("_Quantization"), 0.0),
+        (PF_BOOL,   "ascending", _("_Ascending"), True),
+        (PF_OPTION,   "pchannel",    _("_Partitioning channel"), 3,
+                                            AVAILABLE_CHANNELS),
+        (PF_FLOAT,  "pquantize", _("Partition q_uantization"), 0.0),
     ],
     [],
     palette_sort,
