Adjust luminance for dark/light colors

app/src/main/java/eu/faircode/email/Helper.java

@@ -111,6 +111,8 @@ public class Helper {
     static final int NOTIFICATION_UPDATE = 4;
 
     static final float LOW_LIGHT = 0.6f;
+    static final float MIN_LUMINANCE = 0.33f;
+
     static final int BUFFER_SIZE = 8192; // Same as in Files class
 
     static final String FAQ_URI = "https://github.com/M66B/FairEmail/blob/master/FAQ.md";

app/src/main/java/eu/faircode/email/HtmlHelper.java

@@ -24,6 +24,7 @@ import android.content.SharedPreferences;
 import android.content.res.Resources;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
+import android.graphics.Color;
 import android.graphics.ImageDecoder;
 import android.graphics.Rect;
 import android.graphics.drawable.BitmapDrawable;
@@ -44,6 +45,7 @@ import android.widget.TextView;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.core.graphics.ColorUtils;
 import androidx.core.text.HtmlCompat;
 import androidx.core.util.PatternsCompat;
 import androidx.preference.PreferenceManager;
@@ -145,6 +147,8 @@ public class HtmlHelper {
 
         final Document document = new Cleaner(whitelist).clean(parsed);
 
+        boolean dark = Helper.isDarkTheme(context);
+
         // Sanitize span styles
         for (Element span : document.select("*")) {
             String style = span.attr("style");
@@ -157,12 +161,39 @@ public class HtmlHelper {
                     if (kv.length == 2)
                         switch (kv[0].trim().toLowerCase(Locale.ROOT)) {
                             case "color":
-                                sb.append(param).append(";");
+                                String c = kv[1].trim().toLowerCase(Locale.ROOT);
+                                Integer color = null;
+                                if (!c.startsWith("#"))
+                                    try {
+                                        color = Color.parseColor(c);
+                                    } catch (IllegalArgumentException ex) {
+                                        Log.e("Color=" + c);
+                                    }
+                                if (color == null)
+                                    try {
+                                        color = Integer.decode(c) | 0xFF000000;
+                                    } catch (NumberFormatException ex) {
+                                        Log.e("Color=" + c);
+                                    }
+                                if (color != null) {
+                                    double lum = ColorUtils.calculateLuminance(color);
+                                    if (dark
+                                            ? lum < Helper.MIN_LUMINANCE
+                                            : lum > 1 - Helper.MIN_LUMINANCE)
+                                        color = ColorUtils.blendARGB(color,
+                                                dark ? Color.WHITE : Color.BLACK, Helper.MIN_LUMINANCE);
+                                    c = String.format("#%06x", 0xFFFFFF & color);
+                                    sb.append("color:").append(c).append(";");
+                                }
                                 break;
 
                             case "background":
                             case "background-color":
                                 break;
+
+                            case "line-through":
+                                sb.append(param).append(";");
+                                break;
                         }
                 }
 

app/src/main/java/eu/faircode/email/Identicon.java

@@ -37,7 +37,8 @@ class Identicon {
         byte[] hash = getHash(email);
 
         int color = Color.argb(255, hash[0], hash[1], hash[2]);
-        color = ColorUtils.blendARGB(color, dark ? Color.WHITE : Color.BLACK, 0.2f);
+        color = ColorUtils.blendARGB(color,
+                dark ? Color.WHITE : Color.BLACK, Helper.MIN_LUMINANCE);
 
         Paint paint = new Paint();
         paint.setColor(color);
@@ -76,16 +77,17 @@ class Identicon {
         byte[] hash = getHash(email);
 
         int color = Color.argb(255, hash[0], hash[1], hash[2]);
-        color = ColorUtils.blendARGB(color, dark ? Color.WHITE : Color.BLACK, 0.3f);
+        color = ColorUtils.blendARGB(color,
+                dark ? Color.WHITE : Color.BLACK, Helper.MIN_LUMINANCE);
 
         Bitmap bitmap = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888);
         Canvas canvas = new Canvas(bitmap);
         canvas.drawColor(color);
 
-        float y = (299 * Color.red(color) + 587 * Color.green(color) + 114 * Color.blue(color)) / 1000f;
+        double lum = ColorUtils.calculateLuminance(color);
 
         Paint paint = new Paint();
-        paint.setColor(y < 128 ? Color.WHITE : Color.BLACK);
+        paint.setColor(lum < 0.5 ? Color.WHITE : Color.BLACK);
         paint.setTextSize(size / 2f);
         paint.setTypeface(Typeface.DEFAULT_BOLD);