Convert ColorUtils to Kotlin

Co-authored-by: Alinson S. Xavier <git@axavier.org>

android/android-base/src/main/java/org/isoron/androidbase/utils/ColorUtils.java

@@ -1,66 +0,0 @@
-/*
- * Copyright (C) 2016 Álinson Santos Xavier <isoron@gmail.com>
- *
- * This file is part of Loop Habit Tracker.
- *
- * Loop Habit Tracker is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by the
- * Free Software Foundation, either version 3 of the License, or (at your
- * option) any later version.
- *
- * Loop Habit Tracker is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
- * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program. If not, see <http://www.gnu.org/licenses/>.
- */
-
-package org.isoron.androidbase.utils;
-
-import android.graphics.*;
-
-public abstract class ColorUtils
-{
-    public static int mixColors(int color1, int color2, float amount)
-    {
-        final byte ALPHA_CHANNEL = 24;
-        final byte RED_CHANNEL = 16;
-        final byte GREEN_CHANNEL = 8;
-        final byte BLUE_CHANNEL = 0;
-
-        final float inverseAmount = 1.0f - amount;
-
-        int a = ((int) (((float) (color1 >> ALPHA_CHANNEL & 0xff) * amount) +
-                        ((float) (color2 >> ALPHA_CHANNEL & 0xff) *
-                         inverseAmount))) & 0xff;
-        int r = ((int) (((float) (color1 >> RED_CHANNEL & 0xff) * amount) +
-                        ((float) (color2 >> RED_CHANNEL & 0xff) *
-                         inverseAmount))) & 0xff;
-        int g = ((int) (((float) (color1 >> GREEN_CHANNEL & 0xff) * amount) +
-                        ((float) (color2 >> GREEN_CHANNEL & 0xff) *
-                         inverseAmount))) & 0xff;
-        int b = ((int) (((float) (color1 & 0xff) * amount) +
-                        ((float) (color2 & 0xff) * inverseAmount))) & 0xff;
-
-        return a << ALPHA_CHANNEL | r << RED_CHANNEL | g << GREEN_CHANNEL |
-               b << BLUE_CHANNEL;
-    }
-
-    public static int setAlpha(int color, float newAlpha)
-    {
-        int intAlpha = (int) (newAlpha * 255);
-        return Color.argb(intAlpha, Color.red(color), Color.green(color),
-            Color.blue(color));
-    }
-
-    public static int setMinValue(int color, float newValue)
-    {
-        float hsv[] = new float[3];
-        Color.colorToHSV(color, hsv);
-        hsv[2] = Math.max(hsv[2], newValue);
-        return Color.HSVToColor(hsv);
-    }
-
-}

android/android-base/src/main/java/org/isoron/androidbase/utils/ColorUtils.kt

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2016 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.isoron.androidbase.utils
+
+import android.graphics.Color
+import kotlin.math.max
+
+object ColorUtils {
+    private const val ALPHA_CHANNEL = 24
+    private const val RED_CHANNEL = 16
+    private const val GREEN_CHANNEL = 8
+    private const val BLUE_CHANNEL = 0
+
+    @JvmStatic
+    fun mixColors(color1: Int, color2: Int, amount: Float): Int {
+        val a = mixColorChannel(color1, color2, amount, ALPHA_CHANNEL)
+        val r = mixColorChannel(color1, color2, amount, RED_CHANNEL)
+        val g = mixColorChannel(color1, color2, amount, GREEN_CHANNEL)
+        val b = mixColorChannel(color1, color2, amount, BLUE_CHANNEL)
+        return a or r or g or b
+    }
+
+    @JvmStatic
+    fun setAlpha(color: Int, newAlpha: Float): Int {
+        val intAlpha = (newAlpha * 255).toInt()
+        return Color.argb(intAlpha, Color.red(color), Color.green(color), Color.blue(color))
+    }
+
+    @JvmStatic
+    fun setMinValue(color: Int, newValue: Float): Int {
+        val hsv = FloatArray(3)
+        Color.colorToHSV(color, hsv)
+        hsv[2] = max(hsv[2], newValue)
+        return Color.HSVToColor(hsv)
+    }
+
+    private fun mixColorChannel(color1: Int, color2: Int, amount: Float, channel: Int): Int {
+        val fl = (color1 shr channel and 0xff).toFloat() * amount
+        val f2 = (color2 shr channel and 0xff).toFloat() * (1.0f - amount)
+        return (fl + f2).toInt() and 0xff shl channel
+    }
+}