Replaced the algorithm for determining whether two colors are distinguishable. Merged some duplicated code into its own methods.

app/src/main/java/com/kabouzeid/gramophone/ui/activities/base/AbsSlidingMusicPanelActivity.java

@@ -722,16 +722,12 @@ public abstract class AbsSlidingMusicPanelActivity extends AbsMusicServiceActivi
     private void updateShuffleState() {
         switch (MusicPlayerRemote.getShuffleMode()) {
             case MusicService.SHUFFLE_MODE_SHUFFLE:
-                int activatedColor = colorPlaybackControls
-                        ? getFixedShuffleRepeatButtonColor(lastPlaybackControlsColor)
-                        : ThemeSingleton.get().positiveColor.getDefaultColor();
                 shuffleButton.setImageDrawable(Util.getTintedDrawable(this, R.drawable.ic_shuffle_white_36dp,
-                        activatedColor));
+                        getActivatedIconColor()));
                 break;
             default:
-                int deactivatedColor = ColorUtil.resolveColor(this, android.R.attr.textColorSecondary);
                 shuffleButton.setImageDrawable(Util.getTintedDrawable(this, R.drawable.ic_shuffle_white_36dp,
-                        deactivatedColor));
+                        getDeactivatedIconColor()));
                 break;
         }
     }
@@ -747,34 +743,43 @@ public abstract class AbsSlidingMusicPanelActivity extends AbsMusicServiceActivi
     }
 
     private void updateRepeatState() {
-        int activatedColor = colorPlaybackControls
-                ? getFixedShuffleRepeatButtonColor(lastPlaybackControlsColor)
-                : ThemeSingleton.get().positiveColor.getDefaultColor();
         switch (MusicPlayerRemote.getRepeatMode()) {
             case MusicService.REPEAT_MODE_ALL:
                 repeatButton.setImageDrawable(Util.getTintedDrawable(this, R.drawable.ic_repeat_white_36dp,
-                        activatedColor));
+                        getActivatedIconColor()));
                 break;
             case MusicService.REPEAT_MODE_THIS:
                 repeatButton.setImageDrawable(Util.getTintedDrawable(this, R.drawable.ic_repeat_one_white_36dp,
-                        activatedColor));
+                        getActivatedIconColor()));
                 break;
             default:
-                int deactivatedColor = ColorUtil.resolveColor(this, android.R.attr.textColorSecondary);
                 repeatButton.setImageDrawable(Util.getTintedDrawable(this, R.drawable.ic_repeat_white_36dp,
-                        deactivatedColor));
+                        getDeactivatedIconColor()));
                 break;
         }
     }
 
+    private int getActivatedIconColor() {
+        if (colorPlaybackControls) {
+            return ensureActivatedColorVisibleIfNecessary(lastPlaybackControlsColor);
+        } else {
+            return ThemeSingleton.get().positiveColor.getDefaultColor();
+        }
+    }
+
+    private int getDeactivatedIconColor() {
+        return ColorUtil.resolveColor(this, android.R.attr.textColorSecondary);
+    }
+
     /**
-     * Checks whether the default color and the activated color are similar. If true, returns a darker
+     * @return If the activated color wont have enough difference to the deactivated color Color.WHITE / Color.BLACK (depending on the theme),
-     * activated color. Else, returns the given color as-is.
+     * else the unmodified accentColor.
      */
-    private int getFixedShuffleRepeatButtonColor(int activatedColor) {
+    private int ensureActivatedColorVisibleIfNecessary(int activatedColor) {
-        if (ColorUtil.calculateColorDistance(activatedColor,
+        // Not optimal, but much easier then computing the opaque deactivated color on the background color every time.
-                ColorUtil.resolveColor(this, android.R.attr.textColorSecondary))) {
+        int preBlendedDeactivatedIconColor = ThemeSingleton.get().darkTheme ? Color.argb(255, 188, 188, 188) : Color.argb(255, 115, 115, 115);
-            return ColorUtil.shiftColor(activatedColor, 0.6f);
+        if (ColorUtil.getColorDifference(activatedColor, preBlendedDeactivatedIconColor) <= 30d) {
+            return ThemeSingleton.get().darkTheme ? Color.WHITE : Color.BLACK;
         }
         return activatedColor;
     }

app/src/main/java/com/kabouzeid/gramophone/util/ColorUtil.java

@@ -138,16 +138,91 @@ public class ColorUtil {
         return backgroundColor;
     }
 
+    public static int[] rgb2lab(int R, int G, int B) {
+        //http://www.brucelindbloom.com
+
+        float r, g, b, X, Y, Z, fx, fy, fz, xr, yr, zr;
+        float Ls, as, bs;
+        float eps = 216.f / 24389.f;
+        float k = 24389.f / 27.f;
+
+        float Xr = 0.964221f;  // reference white D50
+        float Yr = 1.0f;
+        float Zr = 0.825211f;
+
+        // RGB to XYZ
+        r = R / 255.f; //R 0..1
+        g = G / 255.f; //G 0..1
+        b = B / 255.f; //B 0..1
+
+        // assuming sRGB (D65)
+        if (r <= 0.04045)
+            r = r / 12;
+        else
+            r = (float) Math.pow((r + 0.055) / 1.055, 2.4);
+
+        if (g <= 0.04045)
+            g = g / 12;
+        else
+            g = (float) Math.pow((g + 0.055) / 1.055, 2.4);
+
+        if (b <= 0.04045)
+            b = b / 12;
+        else
+            b = (float) Math.pow((b + 0.055) / 1.055, 2.4);
+
+
+        X = 0.436052025f * r + 0.385081593f * g + 0.143087414f * b;
+        Y = 0.222491598f * r + 0.71688606f * g + 0.060621486f * b;
+        Z = 0.013929122f * r + 0.097097002f * g + 0.71418547f * b;
+
+        // XYZ to Lab
+        xr = X / Xr;
+        yr = Y / Yr;
+        zr = Z / Zr;
+
+        if (xr > eps)
+            fx = (float) Math.pow(xr, 1 / 3.);
+        else
+            fx = (float) ((k * xr + 16.) / 116.);
+
+        if (yr > eps)
+            fy = (float) Math.pow(yr, 1 / 3.);
+        else
+            fy = (float) ((k * yr + 16.) / 116.);
+
+        if (zr > eps)
+            fz = (float) Math.pow(zr, 1 / 3.);
+        else
+            fz = (float) ((k * zr + 16.) / 116);
+
+        Ls = (116 * fy) - 16;
+        as = 500 * (fx - fy);
+        bs = 200 * (fy - fz);
+
+        int[] lab = new int[3];
+        lab[0] = (int) (2.55 * Ls + .5);
+        lab[1] = (int) (as + .5);
+        lab[2] = (int) (bs + .5);
+        return lab;
+    }
+
     /**
-     * Calculates the distance of two colors in 3D Space.
+     * Computes the difference between two RGB colors by converting them to the L*a*b scale and
+     * comparing them using the CIE76 algorithm { http://en.wikipedia.org/wiki/Color_difference#CIE76}
      *
-     * Taken from http://stackoverflow.com/a/1725535/984061
+     * @return > 23 corresponds to a JND (just noticeable difference)
      */
-    public static boolean calculateColorDistance(int color1, int color2) {
+    public static double getColorDifference(int a, int b) {
-        double red = Math.pow(Math.abs(Color.red(color2) - Color.red(color1)), 2);
+        int r1, g1, b1, r2, g2, b2;
-        double green = Math.pow(Math.abs(Color.green(color2) - Color.green(color1)), 2);
+        r1 = Color.red(a);
-        double blue = Math.pow(Math.abs(Color.blue(color2) - Color.blue(color1)), 2);
+        g1 = Color.green(a);
-        double distance = red + green + blue;
+        b1 = Color.blue(a);
-        return distance < 55000;
+        r2 = Color.red(b);
+        g2 = Color.green(b);
+        b2 = Color.blue(b);
+        int[] lab1 = rgb2lab(r1, g1, b1);
+        int[] lab2 = rgb2lab(r2, g2, b2);
+        return Math.sqrt(Math.pow(lab2[0] - lab1[0], 2) + Math.pow(lab2[1] - lab1[1], 2) + Math.pow(lab2[2] - lab1[2], 2));
     }
 }

app/src/main/res/values/colors.xml

@@ -4,7 +4,7 @@
     <color name="pink_A200">#ff4081</color>
     <color name="indigo_500">#3f51b5</color>
 
-    <color name="grey_800">#424242</color>
+    <color name="grey_700">#616161</color>
     <color name="grey_900">#212121</color>
 
 </resources>

app/src/main/res/values/styles_parents.xml

@@ -43,7 +43,7 @@
 
         <item name="cardBackgroundColor">@color/cardview_light_background</item>
 
-        <item name="default_bar_color">@color/grey_800</item>
+        <item name="default_bar_color">@color/grey_700</item>
 
         <item name="divider_color">@color/md_divider_black</item>
         <item name="icon_color">@color/secondary_text_default_material_light</item>