diff --git a/autoortho/aoconfig.py b/autoortho/aoconfig.py
index 76c5f8ff..8ce5567f 100644
--- a/autoortho/aoconfig.py
+++ b/autoortho/aoconfig.py
@@ -101,6 +101,9 @@ class AOConfig(object):
 
 [windows]
 prefer_winfsp = False
+
+[coloring]
+saturation = 100
 """
 
     def __init__(self, conf_file=None):
diff --git a/autoortho/aoimage/AoImage.py b/autoortho/aoimage/AoImage.py
index 3e3adc47..80ff7301 100755
--- a/autoortho/aoimage/AoImage.py
+++ b/autoortho/aoimage/AoImage.py
@@ -105,10 +105,27 @@ def paste(self, p_img, pos):
         _aoi.aoimage_paste(self, p_img, pos[0], pos[1])
         return True
 
+    def copy(self, height_only = 0):
+        new = AoImage()
+        if not _aoi.aoimage_copy(self, new, height_only):
+            log.error(f"AoImage.copy error: {self._errmsg.decode()}")
+            return None
+
+        return new
+
     def crop(self, c_img, pos):
         _aoi.aoimage_crop(self, c_img, pos[0], pos[1])
         return True
 
+    def desaturate(self, saturation = 1.0):
+        assert 0.0 <= saturation and saturation <= 1.0
+        if saturation == 1.0 or saturation is None:
+            return self
+
+        if not _aoi.aoimage_desaturate(self, saturation):
+            log.error(f"AoImage.desaturate error: {self._errmsg.decode()}")
+            return None
+        return self
 
     @property
     def size(self):
@@ -163,8 +180,10 @@ def open(filename):
 _aoi.aoimage_create.argtypes = (POINTER(AoImage), c_uint32, c_uint32, c_uint32, c_uint32, c_uint32)
 _aoi.aoimage_tobytes.argtypes = (POINTER(AoImage), c_char_p)
 _aoi.aoimage_from_memory.argtypes = (POINTER(AoImage), c_char_p, c_uint32)
+_aoi.aoimage_copy.argtypes = (POINTER(AoImage), POINTER(AoImage), c_uint32)
 _aoi.aoimage_paste.argtypes = (POINTER(AoImage), POINTER(AoImage), c_uint32, c_uint32)
 _aoi.aoimage_crop.argtypes = (POINTER(AoImage), POINTER(AoImage), c_uint32, c_uint32)
+_aoi.aoimage_desaturate.argtypes = (POINTER(AoImage), c_float)
 
 def main():
     logging.basicConfig(level = logging.DEBUG)
@@ -192,6 +211,8 @@ def main():
     img = open("../testfiles/test_tile2.jpg")
     log.info(f"AoImage.open {img}")
 
+    img.copy().desaturate(0.1).write_jpg("desaturated.jpg")
+
     img2 = img.reduce_2()
     log.info(f"img2: {img2}")
 
diff --git a/autoortho/aoimage/aoimage.c b/autoortho/aoimage/aoimage.c
index 7744e65b..2fcc4bc9 100755
--- a/autoortho/aoimage/aoimage.c
+++ b/autoortho/aoimage/aoimage.c
@@ -397,6 +397,32 @@ AOIAPI void aoimage_tobytes(aoimage_t *img, uint8_t *data) {
     memcpy(data, img->ptr, img->width * img->height * img->channels);
 }
 
+AOIAPI int32_t aoimage_copy(const aoimage_t *s_img, aoimage_t *d_img, uint32_t s_height_only) {
+    assert(NULL != s_img->ptr);
+    assert(s_height_only <= s_img->height);
+
+    if (0 == s_height_only)
+        s_height_only = s_img->height;
+
+    int dlen = s_img->width * s_height_only * s_img->channels;
+    uint8_t *dest = malloc(dlen);
+    if (NULL == dest) {
+		sprintf(d_img->errmsg, "can't malloc %d bytes", dlen);
+        d_img->ptr = NULL;
+        return FALSE;
+    }
+
+    memcpy(dest, s_img->ptr, dlen);
+    d_img->ptr = dest;
+    d_img->width = s_img->width;
+    d_img->height = s_height_only;
+    d_img->stride = 4 * d_img->width;
+    d_img->channels = 4;
+    d_img->errmsg[0] = '\0';
+    return TRUE;
+
+}
+
 AOIAPI int32_t aoimage_paste(aoimage_t *img, const aoimage_t *p_img, uint32_t x, uint32_t y) {
     assert(x + p_img->width <= img->width);
     assert(y + p_img->height <= img->height);
@@ -435,4 +461,18 @@ AOIAPI int32_t aoimage_crop(aoimage_t *img, const aoimage_t *c_img, uint32_t x,
     return TRUE;
 }
 
+AOIAPI int32_t aoimage_desaturate(aoimage_t *img, float saturation) {
+    assert(img->channels == 4);
+
+    int len = img->width * img->height * 4;
+    for (uint8_t *ptr = img->ptr; ptr < img->ptr + len; ptr += 4) {
+        float luma = 0.212671 * ptr[0] + 0.715160 * ptr[1] + 0.072169 * ptr[2];
+        float x = (1.0 - saturation) * luma;
+        ptr[0] = (uint8_t)(saturation * ptr[0] + x);
+        ptr[1] = (uint8_t)(saturation * ptr[1] + x);
+        ptr[2] = (uint8_t)(saturation * ptr[2] + x);
+    }
+
+    return TRUE;
+}
 
diff --git a/autoortho/aoimage/aoimage.dll b/autoortho/aoimage/aoimage.dll
index 18f07b51..49cf88b6 100755
Binary files a/autoortho/aoimage/aoimage.dll and b/autoortho/aoimage/aoimage.dll differ
diff --git a/autoortho/aoimage/aoimage.h b/autoortho/aoimage/aoimage.h
index 64f8a763..1c4347ca 100755
--- a/autoortho/aoimage/aoimage.h
+++ b/autoortho/aoimage/aoimage.h
@@ -47,8 +47,12 @@ AOIAPI void aoimage_delete(aoimage_t *img);
 AOIAPI int32_t aoimage_create(aoimage_t *img, uint32_t width, uint32_t height, uint32_t r, uint32_t g, uint32_t b);
 AOIAPI int32_t aoimage_from_memory(aoimage_t *img, const uint8_t *data, uint32_t len);
 AOIAPI void aoimage_tobytes(aoimage_t *img, uint8_t *data);
+AOIAPI int32_t aoimage_copy(const aoimage_t *s_img, aoimage_t *d_img, uint32_t s_height_only);
 
 // in place: img + pasted(p_img)
 AOIAPI int32_t aoimage_paste(aoimage_t *img, const aoimage_t *p_img, uint32_t x, uint32_t y);
 AOIAPI int32_t aoimage_crop(aoimage_t *img, const aoimage_t *c_img, uint32_t x, uint32_t y);
+
+// in place desaturation
+AOIAPI int32_t aoimage_desaturate(aoimage_t *img, float saturation);
 #endif
diff --git a/autoortho/config_ui.py b/autoortho/config_ui.py
index 0029cade..443d1ff0 100644
--- a/autoortho/config_ui.py
+++ b/autoortho/config_ui.py
@@ -171,6 +171,17 @@ def ui_loop(self):
                 #    metadata={'section':self.cfg.cache}
                 #),
             ],
+            [
+                sg.Text('Saturation'),
+                sg.Slider(
+                    range=(0, 100, 5),
+                    default_value = self.cfg.coloring.saturation,
+                    key='saturation',
+                    size=(20,15),
+                    orientation='horizontal',
+                    metadata={'section':self.cfg.coloring}
+                ),
+            ],
             #[
             #    sg.Checkbox('Cleanup cache on start', key='clean_on_start',
             #        default=self.cfg.cache.clean_on_start,
diff --git a/autoortho/getortho.py b/autoortho/getortho.py
index 76072b42..8232a40b 100644
--- a/autoortho/getortho.py
+++ b/autoortho/getortho.py
@@ -421,6 +421,8 @@ def __init__(self, col, row, maptype, zoom, min_zoom=0, priority=0,
                 dxt_format=CFG.pydds.format)
         self.id = f"{row}_{col}_{maptype}_{zoom}"
 
+        # in % in the CFG
+        self.saturation = 0.01 * float(CFG.coloring.saturation)
 
     def __lt__(self, other):
         return self.priority < other.priority
@@ -649,8 +651,18 @@ def get_header(self):
         self.ready.set()
         return outfile
 
-    @locked
     def get_img(self, mipmap, startrow=0, endrow=None, maxwait=5, min_zoom=None):
+        im = self._get_img(mipmap, startrow, endrow, maxwait, min_zoom)
+        if im is None:
+            return None
+
+        if self.saturation < 1.0:
+            im = im.copy().desaturate(self.saturation)
+
+        return im
+
+    @locked
+    def _get_img(self, mipmap, startrow=0, endrow=None, maxwait=5, min_zoom=None):
         #
         # Get an image for a particular mipmap
         #