add OklabColor implementation/tests

co-lors · Aug 4, 2024 · 9d3f385 · 9d3f385
1 parent 84027fc
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Showing 6 changed files with 252 additions and 8 deletions.
diff --git a/src/main/java/co/lors/Color.java b/src/main/java/co/lors/Color.java
@@ -1,18 +1,23 @@
 package co.lors;
 
-public sealed interface Color permits RgbColor {
+public sealed interface Color permits RgbColor, OklabColor {
 
   static Color parse(String value) {
     if (value.startsWith("#")) {
       return RgbColor.fromHex(value);
     } else if (value.startsWith("rgb")) {
       return RgbColor.fromCss(value);
+    } else if (value.startsWith("oklab")) {
+      return OklabColor.fromCss(value);
     }
-    // todo: handle more colorspaces
 
     throw new UnsupportedOperationException("Colorspace of " + value + " is unsupported!");
   }
 
   String toCss();
 
+  RgbColor toRgb();
+
+  OklabColor toOklab();
+
 }
diff --git a/src/main/java/co/lors/OklabColor.java b/src/main/java/co/lors/OklabColor.java
@@ -0,0 +1,94 @@
+package co.lors;
+
+/**
+ * A type representing an Oklab color with optional transparency.
+ *
+ * It uses the <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/color_value/oklab">Oklab</a> colorspace,
+ * which uses the D65 white point.
+ * Compared to sRGB, it can express a wider range of colors.
+ */
+public record OklabColor(float lightness, float aAxis, float bAxis, float alpha) implements Color {
+
+  public OklabColor {
+    checkUnitRange("lightness", lightness);
+    checkAxisRange("aAxis", aAxis);
+    checkAxisRange("bAxis", bAxis);
+    checkUnitRange("alpha", alpha);
+  }
+
+  public static OklabColor of(float lightness, float aAxis, float bAxis, float alpha) {
+    return new OklabColor(lightness, aAxis, bAxis, alpha);
+  }
+
+  public static OklabColor of(float lightness, float aAxis, float bAxis) {
+    return new OklabColor(lightness, aAxis, bAxis, 1.0f);
+  }
+
+  public static OklabColor fromCss(String value) {
+    String[] colors = value.substring(7, value.length() - 1).split(" / |, |,| ");
+    float lightness = Float.parseFloat(colors[0].trim());
+    float aAxis = Float.parseFloat(colors[1].trim());
+    float bAxis = Float.parseFloat(colors[2].trim());
+    float alpha = 1.0f;
+    if (colors.length > 3) {
+      alpha = Float.parseFloat(colors[3].trim());
+    }
+    return OklabColor.of(lightness, aAxis, bAxis, alpha);
+  }
+
+  @Override
+  public String toCss() {
+    String alphaString = alpha == 0.0f ? "" : " / " + alpha;
+    return "oklab(" + lightness + " " + aAxis + " " + bAxis + alphaString + ")";
+  }
+
+  @Override
+  public RgbColor toRgb() {
+      double l = lightness + 0.3963377774 * aAxis + 0.2158037573 * bAxis;
+      double m = lightness - 0.1055613458 * aAxis - 0.0638541728 * bAxis;
+      double s = lightness - 0.0894841775 * aAxis - 1.2914855480 * bAxis;
+
+      double l3 = l * l * l;
+      double m3 = m * m * m;
+      double s3 = s * s * s;
+
+    double red = +4.0767416621 * l3 - 3.3077115913 * m3 + 0.2309699292 * s3;
+    double green = -1.2684380046 * l3 + 2.6097574011 * m3 - 0.3413193965 * s3;
+    double blue = -0.0041960863 * l3 - 0.7034186147 * m3 + 1.7076147010 * s3;
+    return RgbColor.of(scaleToByte(red), scaleToByte(green), scaleToByte(blue), (int) (alpha * 255));
+  }
+
+  @Override
+  public OklabColor toOklab() {
+    return this;
+  }
+
+  private static double gamma(double value) {
+    return value >= 0.0031308
+        ? 1.055 * Math.pow(value, 1 / 2.4) - 0.055
+        : 12.92 * value;
+  }
+
+  private static int scaleToByte(double value) {
+    return Math.max(0, Math.min(255, (int) (Math.round(gamma(value) * 255))));
+  }
+
+  private static void checkUnitRange(String name, float value) {
+    if (value < 0) {
+      throw new IllegalArgumentException(name + " cannot be less than 0, but was " + value);
+    }
+    if (value > 1) {
+      throw new IllegalArgumentException(name + " cannot be greater than 1, but was " + value);
+    }
+  }
+
+  private static void checkAxisRange(String name, float value) {
+    if (value < -0.4f) {
+      throw new IllegalArgumentException(name + " cannot be less than -0.4, but was " + value);
+    }
+    if (value > 0.4f) {
+      throw new IllegalArgumentException(name + " cannot be greater than 0.4, but was " + value);
+    }
+  }
+
+}
diff --git a/src/main/java/co/lors/RgbColor.java b/src/main/java/co/lors/RgbColor.java
@@ -41,19 +41,19 @@ public static RgbColor fromHex(String value) {
     if (value.length() == 3 || value.length() == 6 || value.length() == 8) {
       value = '#' + value;
     }
-    int intval = Integer.decode(value);
+    long intval = Long.decode(value);
     if (value.length() == 4) { // color shorthand?
-      int red = intval & 0xF00;
-      int green = intval & 0x0F0;
-      int blue = intval & 0x00F;
+      int red = (int) (intval & 0xF00);
+      int green = (int) (intval & 0x0F0);
+      int blue = (int) (intval & 0x00F);
       intval = red << 20 | red << 16;
       intval |= green << 16 | green << 12;
       intval |= blue << 12 | blue << 8;
       intval |= 0xFF;
     } else if (value.length() == 7) { // alpha missing?
       intval = (intval << 8) | 0xFF;
     }
-    return new RgbColor(intval);
+    return new RgbColor((int) intval);
   }
 
   /** `RRGGBBAA` */
@@ -74,7 +74,7 @@ public String toHexWithHash() {
 
   /** `rgb(r, g, b, a)` */
   public static RgbColor fromCss(String value) {
-    String[] colors = value.substring(4, value.length() - 1).split(",");
+    String[] colors = value.substring(4, value.length() - 1).split(" / |, |,| ");
     int r = Integer.parseInt(colors[0].trim());
     int g = Integer.parseInt(colors[1].trim());
     int b = Integer.parseInt(colors[2].trim());
@@ -93,6 +93,36 @@ public String toCss() {
     return "rgb(" + red() + ", " + green() + ", " + blue() + ", " + df.format(alphaScaled()) + ")";
   }
 
+  @Override
+  public RgbColor toRgb() {
+    return this;
+  }
+
+  @Override
+  public OklabColor toOklab() {
+    double r = gammaInv(red() / 255.0);
+    double g = gammaInv(green() / 255.0);
+    double b = gammaInv(blue() / 255.0);
+
+    double l3 = 0.4121656120 * r + 0.5362752080 * g + 0.0514575653 * b;
+    double m3 = 0.2118591070 * r + 0.6807189584 * g + 0.1074065790 * b;
+    double s3 = 0.0883097947 * r + 0.2818474174 * g + 0.6302613616 * b;
+
+    double l = Math.cbrt(l3);
+    double m = Math.cbrt(m3);
+    double s = Math.cbrt(s3);
+
+    return new OklabColor(
+        (float) (0.2104542553 * l + 0.7936177850 * m - 0.0040720468 * s),
+        (float) (1.9779984951 * l - 2.4285922050 * m + 0.4505937099 * s),
+        (float) (0.0259040371 * l + 0.7827717662 * m - 0.8086757660 * s),
+        (float) alphaScaled());
+  }
+
+  private static double gammaInv(double r) {
+    return (r > 0.04045) ? Math.pow((r + 0.055) / 1.055, 2.4) : (r / 12.92);
+  }
+
   public int red() {
     return (value >> 24) & 0xFF;
   }

diff --git a/src/test/java/co/lors/ColorTest.java b/src/test/java/co/lors/ColorTest.java
@@ -0,0 +1,21 @@
+package co.lors;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ColorTest {
+
+  @Test
+  void parse() {
+    assertEquals(RgbColor.of(255, 204, 153), Color.parse("#FFCC99"));
+    assertEquals(RgbColor.of(255, 204, 153, 34), Color.parse("#FFCC9922"));
+
+    assertEquals(RgbColor.of(255, 204, 153), Color.parse("rgb(255, 204, 153)"));
+    assertEquals(RgbColor.of(255, 204, 153, 34), Color.parse("rgb(255, 204, 153 / 0.133)"));
+
+    assertEquals(OklabColor.of(0.700f, 0.200f, 0.000f), Color.parse("oklab(0.7 0.2 0.0)"));
+    assertEquals(OklabColor.of(0.700f, 0.200f, 0.000f, 1.0f), Color.parse("oklab(0.7 0.2 0.0 / 1.0)"));
+  }
+
+}
diff --git a/src/test/java/co/lors/OklabColorTest.java b/src/test/java/co/lors/OklabColorTest.java
@@ -0,0 +1,54 @@
+package co.lors;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class OklabColorTest {
+
+  public static final OklabColor COLOR1 = OklabColor.of(0.700f, 0.200f, 0.000f, 1.0f);
+  public static final OklabColor COLOR2 = OklabColor.of(0.500f, 0.100f, 0.100f, 1.0f);
+
+  @Test
+  void fromCss() {
+    assertEquals(COLOR1, OklabColor.fromCss("oklab(0.7 0.2 0.0 / 1.0)"));
+    assertEquals(COLOR2, OklabColor.fromCss("oklab(0.5 0.1 0.1 / 1.0)"));
+  }
+
+  @Test
+  void toCss() {
+    assertEquals(COLOR1.toCss(), "oklab(0.7 0.2 0.0 / 1.0)");
+    assertEquals(COLOR2.toCss(), "oklab(0.5 0.1 0.1 / 1.0)");
+  }
+
+  @Test
+  void toRgb() {
+    assertEquals(COLOR1.toRgb(), RgbColor.of(251, 92, 153, 255));
+    assertEquals(COLOR2.toRgb(), RgbColor.of(161, 66, 3, 255));
+  }
+
+  @Test
+  void lightness() {
+    assertEquals(COLOR1.lightness(), 0.7f);
+    assertEquals(COLOR2.lightness(), 0.5f);
+  }
+
+  @Test
+  void aAxis() {
+    assertEquals(COLOR1.aAxis(), 0.2f);
+    assertEquals(COLOR2.aAxis(), 0.1f);
+  }
+
+  @Test
+  void bAxis() {
+    assertEquals(COLOR1.bAxis(), 0.0f);
+    assertEquals(COLOR2.bAxis(), 0.1f);
+  }
+
+  @Test
+  void alpha() {
+    assertEquals(COLOR1.alpha(), 1.0f);
+    assertEquals(COLOR2.alpha(), 1.0f);
+  }
+
+}
diff --git a/src/test/java/co/lors/RgbColorTest.java b/src/test/java/co/lors/RgbColorTest.java
@@ -163,6 +163,46 @@ public void toHexHash5NoAlpha() {
 
   @Test
   public void fromCss() {
+    assertEquals(RgbColor.BLACK, RgbColor.fromCss("rgb(0 0 0 1.0)"));
+    assertEquals(RgbColor.WHITE, RgbColor.fromCss("rgb(255 255, 255 1.0)"));
+    assertEquals(RgbColor.RED, RgbColor.fromCss("rgb(255 0 0 1.0)"));
+    assertEquals(RgbColor.GREEN, RgbColor.fromCss("rgb(0 255 0 1.0)"));
+    assertEquals(RgbColor.BLUE, RgbColor.fromCss("rgb(0 0 255 1.0)"));
+
+    assertEquals(RgbColor.of(0, 0, 0, 0), RgbColor.fromCss("rgb(0 0 0 0.0)"));
+    assertEquals(RgbColor.of(0, 0, 0, 1), RgbColor.fromCss("rgb(0 0 0 0.004)"));
+    assertEquals(RgbColor.of(0, 0, 0, 2), RgbColor.fromCss("rgb(0 0 0 0.008)"));
+    assertEquals(RgbColor.of(0, 0, 0, 11), RgbColor.fromCss("rgb(0 0 0 0.043)"));
+    assertEquals(RgbColor.of(0, 0, 0, 23), RgbColor.fromCss("rgb(0 0 0 0.09)"));
+    assertEquals(RgbColor.of(0, 0, 0, 42), RgbColor.fromCss("rgb(0 0 0 0.165)"));
+    assertEquals(RgbColor.of(0, 0, 0, 59), RgbColor.fromCss("rgb(0 0 0 0.231)"));
+    assertEquals(RgbColor.of(0, 0, 0, 113), RgbColor.fromCss("rgb(0 0 0 0.443)"));
+    assertEquals(RgbColor.of(0, 0, 0, 127), RgbColor.fromCss("rgb(0 0 0 0.498)"));
+    assertEquals(RgbColor.of(0, 0, 0, 128), RgbColor.fromCss("rgb(0 0 0 0.502)"));
+    assertEquals(RgbColor.of(0, 0, 0, 129), RgbColor.fromCss("rgb(0 0 0 0.506)"));
+    assertEquals(RgbColor.of(0, 0, 0, 253), RgbColor.fromCss("rgb(0 0 0 0.992)"));
+    assertEquals(RgbColor.of(0, 0, 0, 254), RgbColor.fromCss("rgb(0 0 0 0.996)"));
+    assertEquals(RgbColor.of(0, 0, 0, 255), RgbColor.fromCss("rgb(0 0 0 1.0)"));
+
+    // values without rounding to max 3 fractional digits
+    assertEquals(RgbColor.of(0, 0, 0, 0), RgbColor.fromCss("rgb(0 0 0 0.0)"));
+    assertEquals(RgbColor.of(0, 0, 0, 1), RgbColor.fromCss("rgb(0 0 0 0.00392156862745098)"));
+    assertEquals(RgbColor.of(0, 0, 0, 2), RgbColor.fromCss("rgb(0 0 0 0.00784313725490196)"));
+    assertEquals(RgbColor.of(0, 0, 0, 11), RgbColor.fromCss("rgb(0 0 0 0.043137254901960784)"));
+    assertEquals(RgbColor.of(0, 0, 0, 23), RgbColor.fromCss("rgb(0 0 0 0.09019607843137255)"));
+    assertEquals(RgbColor.of(0, 0, 0, 42), RgbColor.fromCss("rgb(0 0 0 0.16470588235294117)"));
+    assertEquals(RgbColor.of(0, 0, 0, 59), RgbColor.fromCss("rgb(0 0 0 0.23137254901960785)"));
+    assertEquals(RgbColor.of(0, 0, 0, 113), RgbColor.fromCss("rgb(0 0 0 0.44313725490196076)"));
+    assertEquals(RgbColor.of(0, 0, 0, 127), RgbColor.fromCss("rgb(0 0 0 0.4980392156862745)"));
+    assertEquals(RgbColor.of(0, 0, 0, 128), RgbColor.fromCss("rgb(0 0 0 0.5019607843137255)"));
+    assertEquals(RgbColor.of(0, 0, 0, 129), RgbColor.fromCss("rgb(0 0 0 0.5058823529411764)"));
+    assertEquals(RgbColor.of(0, 0, 0, 253), RgbColor.fromCss("rgb(0 0 0 0.9921568627450981)"));
+    assertEquals(RgbColor.of(0, 0, 0, 254), RgbColor.fromCss("rgb(0 0 0 0.996078431372549)"));
+    assertEquals(RgbColor.of(0, 0, 0, 255), RgbColor.fromCss("rgb(0 0 0 1.0)"));
+  }
+
+  @Test
+  public void fromCssLegacyCommaSyntax() {
     assertEquals(RgbColor.BLACK, RgbColor.fromCss("rgb(0, 0, 0, 1.0)"));
     assertEquals(RgbColor.WHITE, RgbColor.fromCss("rgb(255, 255, 255, 1.0)"));
     assertEquals(RgbColor.RED, RgbColor.fromCss("rgb(255, 0, 0, 1.0)"));