Merge pull request #120 from facelessuser/feature/lch-chroma

Use lch-chroma as the default again

coloraide/util.py

@@ -23,7 +23,7 @@
 DEF_MIX = 0.5
 DEF_HUE_ADJ = "shorter"
 DEF_INTERPOLATE = "oklab"
-DEF_FIT = "oklch-chroma"
+DEF_FIT = "lch-chroma"
 DEF_DELTA_E = "76"
 
 ERR_MAP_MSG = """

docs/src/markdown/about/changelog.md

@@ -2,6 +2,8 @@
 
 ## 0.10.0
 
+- **NEW**: Switch back to using CIELCH for gamut mapping (`lch-chroma`). There are still some edge cases that make
+  `oklch-chroma` less desirable.
 - **FIX**: Fix an issue where when attempting to generate steps some ∆E distance apart, the maximum step range was not
   respected and could result in large hangs.
 

docs/src/markdown/gamut.md

@@ -131,15 +131,14 @@ There are various different ways to gamut map a color into a smaller gamut. Curr
 Method         | Description
 -------------- | -----------
 `clip`         | Simple, naive clipping.
-`oklch-chroma` | Compress chroma in the Oklch color space to bring a color in gamut. This is the default method used.
-`lch-chroma`   | This is like `oklch-chroma` but is done with CIELCH. This is what ColorAide originally used before `oklch-chroma`. Hue preservation is not as good. This method may be removed at some future point as it does not hold the hue as well as Oklch.
+`lch-chroma`   | Uses chroma reduction in the CIELCH color space to bring a color into gamut. This is the default method used.
+`oklch-chroma` | Like `lch-chroma`, but uses the Oklch color space instead. Currently experimental.
 
 !!! note "CSS Level 4 Gamut Mapping"
-    We do currently use the algorithm as defined in the [CSS Level 4 specification](https://drafts.csswg.org/css-color/#binsearch).
-    This is because the current algorithm, as defined, has some issues that create gradients that are not smooth.
-    We currently feel the algorithm we are using does a better job as it creates smooth gradients without odd
-    discontinuities. If/when the CSS Level 4 specification is updated to address such concerns, we may align more
-    closely.
+    We do not currently use the algorithm as defined in the [CSS Level 4 specification](https://drafts.csswg.org/css-color/#binsearch).
+    This is because the current algorithm, as defined, has some issues that create gradients that are not smooth and
+    can create unexpected colors in some situations. If/when the CSS Level 4 specification is updated to address such
+    concerns, we may align more closely.
 
 In this example, we will take the color `#!color lch(100% 50 75)`. CIELCH's gamut is technically unbounded, but when we
 convert the color to sRGB, we find that the color is out of gamut. So, using the `fit` method, we can actually transform
@@ -178,14 +177,14 @@ Color("lch(100% 50 75)").fit("srgb", method='clip')
 
 If we wanted to change the default "fitting" to `clip`, we can also just use a
 [class override](./color.md#override-default-settings). Doing this will cause the class to default to `clip` any time a
-color needs to be mapped. Though, you can still use chroma compression by specifying `oklch-chroma` for the `method`.
+color needs to be mapped. Though, you can still use chroma compression by specifying `lch-chroma` for the `method`.
 
 ```playground
 class Custom(Color):
     FIT = 'clip'
 
 Custom("lch(100% 50 75)").convert('srgb').fit()
-Custom("lch(100% 50 75)").convert('srgb').fit(method='oklch-chroma')
+Custom("lch(100% 50 75)").convert('srgb').fit(method='lch-chroma')
 ```
 
 It is important to note that when using fit, there is no tolerance, so even if `in_gamut` allowed enough tolerance to

mkdocs.yml

@@ -122,7 +122,7 @@ extra_css:
   - assets/coloraide-extras/extra-ccd229caf0.css
 extra_javascript:
   - https://cdn.jsdelivr.net/pyodide/v0.19.0/full/pyodide.js
-  - assets/coloraide-extras/extra-notebook-8732391e.js
+  - assets/coloraide-extras/extra-notebook-678306ab.js
 
 extra:
   social:

tests/test_a98_rgb.py

@@ -66,7 +66,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(a98-rgb 2 -1 0)').to_string(),
-            'color(a98-rgb 1 1 1)'
+            'color(a98-rgb 1 0.84447 0.82443)'
         )
 
         self.assertEqual(

tests/test_api.py

@@ -1502,7 +1502,7 @@ class Color2(Color):
 
         self.assertEqual(
             Color('color(srgb 2 -1 0)').fit().to_string(),
-            'rgb(255 153.85 169.85)'
+            'rgb(255 117.89 100.38)'
         )
 
         self.assertEqual(

tests/test_display_p3.py

@@ -66,7 +66,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(display-p3 2 -1 0)').to_string(),
-            'color(display-p3 1 0.74486 0.77344)'
+            'color(display-p3 1 0.60349 0.48071)'
         )
 
         self.assertEqual(

tests/test_hsl.py

@@ -168,7 +168,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(--hsl 20 150% 75%)').to_string(),
-            'hsl(19.317 100% 77.159%)'
+            'hsl(19.891 100% 76.496%)'
         )
 
         self.assertEqual(

tests/test_hsv.py

@@ -66,7 +66,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(--hsv 20 1.5 0.75)').to_string(),
-            'color(--hsv 51.799 1 0.45576)'
+            'color(--hsv 40.492 1 0.50528)'
         )
 
         self.assertEqual(

tests/test_hwb.py

@@ -136,7 +136,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(--hwb 20 0% -55%)').to_string(),
-            'hwb(14.271 82.804% 0%)'
+            'hwb(17.844 77.324% 0%)'
         )
 
         self.assertEqual(

tests/test_okhsl.py

@@ -76,7 +76,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(--okhsl 50 40% 110%)').to_string(),
-            'color(--okhsl 0 0 1)'
+            'color(--okhsl 90 0 1)'
         )
 
         self.assertEqual(

tests/test_okhsv.py

@@ -66,7 +66,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(--okhsv 20 150% 75%)').to_string(),
-            'color(--okhsv 20 1 0.60559)'
+            'color(--okhsv 23.815 1 0.57453)'
         )
 
         self.assertEqual(

tests/test_prophoto_rgb.py

@@ -66,7 +66,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(prophoto-rgb 2 -1 0)').to_string(),
-            'color(prophoto-rgb 1 0.38166 0.5562)'
+            'color(prophoto-rgb 1 0 0.25853)'
         )
 
         self.assertEqual(

tests/test_rec2020.py

@@ -66,7 +66,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(rec2020 2 -1 0)').to_string(),
-            'color(rec2020 1 0.72306 0.76062)'
+            'color(rec2020 1 0.51313 0.38209)'
         )
 
         self.assertEqual(

tests/test_srgb.py

@@ -299,7 +299,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(srgb 2 -1 0)').to_string(),
-            'rgb(255 153.85 169.85)'
+            'rgb(255 117.89 100.38)'
         )
 
         self.assertEqual(

tests/test_srgb_linear.py

@@ -66,7 +66,7 @@ def test_fit(self):
 
         self.assertEqual(
             Color('color(srgb-linear 2 0 0)').to_string(),
-            'color(srgb-linear 1 0.29816 0.22913)'
+            'color(srgb-linear 1 0.26331 0.14651)'
         )
 
         self.assertEqual(