Automatically pick text color based on back color

app/build.gradle

@@ -3,13 +3,13 @@ apply plugin: 'com.android.application'
 group = 'com.github.rafakob'
 
 android {
-    compileSdkVersion 23
-    buildToolsVersion "23.0.2"
+    compileSdkVersion rootProject.ext.CompileSdk
+    buildToolsVersion rootProject.ext.BuildTools
 
     defaultConfig {
         applicationId "com.rafakob.example.drawme"
-        minSdkVersion 10
-        targetSdkVersion 23
+        minSdkVersion rootProject.ext.MinSdk
+        targetSdkVersion rootProject.ext.TargetSdk
         versionCode 1
         versionName "1.0.0"
     }
@@ -24,7 +24,7 @@ android {
 dependencies {
     compile fileTree(dir: 'libs', include: ['*.jar'])
     testCompile 'junit:junit:4.12'
-    compile 'com.android.support:appcompat-v7:23.2.1'
+    compile "com.android.support:appcompat-v7:$rootProject.ext.SupportLibrary"
 
     compile project(':library')
 }

build.gradle

@@ -3,15 +3,23 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.0.0-rc1'
-        classpath 'com.github.dcendents:android-maven-gradle-plugin:1.3'
+        classpath 'com.android.tools.build:gradle:2.3.2'
+        classpath 'com.github.dcendents:android-maven-gradle-plugin:1.5'
     }
 }
 
 allprojects {
     repositories {
         jcenter()
     }
+
+    rootProject.ext {
+        BuildTools = "25.0.2"
+        MinSdk = 10
+        TargetSdk = 25
+        CompileSdk = 25
+        SupportLibrary = "25.3.1"
+    }
 }
 
 task clean(type: Delete) {

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Mon Dec 28 10:00:20 PST 2015
+#Thu Jun 08 19:35:26 PST 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-2.10-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-3.5-all.zip

library/build.gradle

@@ -6,15 +6,16 @@ def versionMinor = 1
 def versionPatch = 6
 
 android {
-    compileSdkVersion 23
-    buildToolsVersion "23.0.2"
+    compileSdkVersion rootProject.ext.CompileSdk
+    buildToolsVersion rootProject.ext.BuildTools
 
     defaultConfig {
-        minSdkVersion 10
-        targetSdkVersion 23
+        minSdkVersion rootProject.ext.MinSdk
+        targetSdkVersion rootProject.ext.TargetSdk
         versionCode versionMajor * 1000000 + versionMinor * 1000 + versionPatch
         versionName "${versionMajor}.${versionMinor}.${versionPatch}"
     }
+
     buildTypes {
         release {
             minifyEnabled false
@@ -26,7 +27,7 @@ android {
 dependencies {
     compile fileTree(dir: 'libs', include: ['*.jar'])
     testCompile 'junit:junit:4.12'
-    compile 'com.android.support:appcompat-v7:23.2.1'
+    compile "com.android.support:appcompat-v7:$rootProject.ext.SupportLibrary"
 }
 
 // build a jar with source files

library/src/main/java/com/rafakob/drawme/delegate/DrawMeShapeText.java

@@ -3,10 +3,13 @@
 import android.content.Context;
 import android.content.res.ColorStateList;
 import android.content.res.TypedArray;
+import android.graphics.Color;
 import android.graphics.PorterDuff;
 import android.graphics.drawable.Drawable;
 import android.os.Build;
 import android.support.annotation.AttrRes;
+import android.support.annotation.ColorInt;
+import android.support.annotation.FloatRange;
 import android.support.v4.graphics.drawable.DrawableCompat;
 import android.text.TextUtils;
 import android.util.AttributeSet;
@@ -38,7 +41,7 @@ public DrawMeShapeText(Context context, View view, AttributeSet attrs, @AttrRes
 
     protected void obtainTextAttributes(TypedArray a) {
         font = a.getString(R.styleable.DrawMeText_dm_font);
-        textColor = a.getColor(R.styleable.DrawMeText_dm_textColor, ((TextView) mView).getTextColors().getDefaultColor());
+        textColor = a.getColor(R.styleable.DrawMeText_dm_textColor, getTitleColor(backColor));
         textColorPressed = a.getColor(R.styleable.DrawMeText_dm_textColorPressed, textColor);
         textColorDisabled = a.getColor(R.styleable.DrawMeText_dm_textColorDisabled, textColor);
 
@@ -152,4 +155,18 @@ public void updateLayout() {
             ((TextView) mView).setTextColor(colorStateList);
         }
     }
+
+    @ColorInt
+    private int getTitleColor(@ColorInt int color) {
+        double darkness = 1-(0.299* Color.red(color) + 0.587*Color.green(color) + 0.114*Color.blue(color))/255;
+        return (darkness < 0.35) ? getDarkerColor(color, 0.25f) : Color.WHITE;
+    }
+
+    @ColorInt
+    private int getDarkerColor(@ColorInt int color, @FloatRange(from = 0.0f, to = 1.0f) float transparency) {
+        float[] hsv = new float[3];
+        Color.colorToHSV(color, hsv);
+        hsv[2] *= transparency;
+        return Color.HSVToColor(hsv);
+    }
 }