Add Kotlin encoder

Kotlin/demo/build.gradle

@@ -26,4 +26,5 @@ android {
 dependencies {
     implementation project(path: ':lib')
     implementation 'androidx.appcompat:appcompat:1.1.0'
+    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
 }

Kotlin/demo/src/main/java/com/wolt/blurhashapp/MainActivity.kt

@@ -1,24 +1,53 @@
 package com.wolt.blurhashapp
 
+import android.graphics.Bitmap
+import android.graphics.Canvas
+import android.graphics.drawable.BitmapDrawable
+import android.graphics.drawable.Drawable
 import android.os.Bundle
 import android.view.View
-import android.widget.EditText
-import android.widget.ImageView
-import android.widget.TextView
 import androidx.appcompat.app.AppCompatActivity
+import androidx.core.content.ContextCompat
 import com.wolt.blurhashkt.BlurHashDecoder
+import com.wolt.blurhashkt.BlurHashEncoder
+import kotlinx.android.synthetic.main.activity_main.*
 
 class MainActivity : AppCompatActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
-        val etInput: EditText = findViewById(R.id.etInput)
-        val ivResult: ImageView = findViewById(R.id.ivResult)
-        findViewById<View>(R.id.tvDecode).setOnClickListener {
+
+        btnDecode.setOnClickListener {
             val bitmap = BlurHashDecoder.decode(etInput.text.toString(), 20, 12)
             ivResult.setImageBitmap(bitmap)
         }
+
+        val buttons = listOf(btnEncode1, btnEncode2, btnEncode3, btnEncode4, btnEncode5)
+        val drawableResList = listOf(R.drawable.img1, R.drawable.img2, R.drawable.img3, R.drawable.img4, R.drawable.img5)
+        val onClickListener = View.OnClickListener {
+            val bitmap = drawableToBitmap(ContextCompat.getDrawable(this, drawableResList[buttons.indexOf(it)])!!)
+            etInput.setText(BlurHashEncoder.encode(bitmap))
+        }
+        for (button in buttons) {
+            button.setOnClickListener(onClickListener)
+        }
+    }
+
+    private fun drawableToBitmap(drawable: Drawable): Bitmap {
+        return drawableToBitmap(drawable, drawable.intrinsicWidth,
+                drawable.intrinsicHeight)
+    }
+
+    private fun drawableToBitmap(drawable: Drawable, w: Int, h: Int): Bitmap {
+        if (drawable is BitmapDrawable) {
+            return drawable.bitmap
+        }
+        val bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888)
+        val canvas = Canvas(bitmap)
+        drawable.setBounds(0, 0, canvas.width, canvas.height)
+        drawable.draw(canvas)
+        return bitmap
     }
 
 }

Kotlin/demo/src/main/res/layout/activity_main.xml

@@ -1,43 +1,116 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:orientation="vertical"
     android:padding="24dp">
 
     <EditText
         android:id="@+id/etInput"
-        android:layout_width="match_parent"
+        android:layout_width="0dp"
         android:layout_height="wrap_content"
-        android:layout_gravity="center_horizontal"
+        android:autofillHints="@null"
         android:gravity="center_horizontal"
         android:hint="@string/hint_blurhash"
         android:inputType="text"
-        android:singleLine="true"
-        android:text="LEHV6nWB2yk8pyo0adR*.7kCMdnj"
-        android:textColor="@color/colorAccent" />
+        android:maxLines="1"
+        android:text="@string/demo_blurhash_string"
+        android:textColor="@color/textColor"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
 
-    <TextView
-        android:id="@+id/tvDecode"
-        android:layout_width="wrap_content"
+    <Button
+        android:id="@+id/btnDecode"
+        style="@style/Widget.AppCompat.Button.Colored"
+        android:layout_width="0dp"
         android:layout_height="wrap_content"
-        android:layout_gravity="center_horizontal"
         android:layout_marginTop="12dp"
-        android:background="@color/colorPrimary"
-        android:elevation="8dp"
-        android:paddingStart="12dp"
-        android:paddingTop="8dp"
-        android:paddingEnd="12dp"
-        android:paddingBottom="8dp"
         android:text="@string/title_button_decode"
-        android:textColor="@color/colorAccent"
-        android:textSize="16sp" />
+        android:textColor="@color/textColor"
+        android:textSize="16sp"
+        app:layout_constraintEnd_toStartOf="@id/btnEncode1"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/etInput" />
+
+    <Button
+        android:id="@+id/btnEncode1"
+        style="@style/Widget.AppCompat.Button.Colored"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginLeft="8dp"
+        android:layout_marginTop="12dp"
+        android:layout_marginRight="8dp"
+        android:text="@string/title_button_encode1"
+        android:textColor="@color/textColor"
+        android:textSize="16sp"
+        app:layout_constraintEnd_toStartOf="@id/btnEncode2"
+        app:layout_constraintStart_toEndOf="@id/btnDecode"
+        app:layout_constraintTop_toBottomOf="@id/etInput" />
+
+    <Button
+        android:id="@+id/btnEncode2"
+        style="@style/Widget.AppCompat.Button.Colored"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="12dp"
+        android:text="@string/title_button_encode2"
+        android:textColor="@color/textColor"
+        android:textSize="16sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toEndOf="@id/btnEncode1"
+        app:layout_constraintTop_toBottomOf="@id/etInput" />
+
+    <Button
+        android:id="@+id/btnEncode3"
+        style="@style/Widget.AppCompat.Button.Colored"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="8dp"
+        android:text="@string/title_button_encode3"
+        android:textColor="@color/textColor"
+        android:textSize="16sp"
+        app:layout_constraintEnd_toStartOf="@id/btnEncode4"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/btnDecode" />
+
+    <Button
+        android:id="@+id/btnEncode4"
+        style="@style/Widget.AppCompat.Button.Colored"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginLeft="8dp"
+        android:layout_marginTop="8dp"
+        android:layout_marginRight="8dp"
+        android:text="@string/title_button_encode4"
+        android:textColor="@color/textColor"
+        android:textSize="16sp"
+        app:layout_constraintEnd_toStartOf="@id/btnEncode5"
+        app:layout_constraintStart_toEndOf="@id/btnEncode3"
+        app:layout_constraintTop_toBottomOf="@id/btnDecode" />
+
+    <Button
+        android:id="@+id/btnEncode5"
+        style="@style/Widget.AppCompat.Button.Colored"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="8dp"
+        android:text="@string/title_button_encode5"
+        android:textColor="@color/textColor"
+        android:textSize="16sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toEndOf="@id/btnEncode4"
+        app:layout_constraintTop_toBottomOf="@id/btnDecode" />
 
     <ImageView
         android:id="@+id/ivResult"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_marginTop="24dp"
-        android:adjustViewBounds="true" />
+        android:adjustViewBounds="true"
+        android:contentDescription="@null"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/btnEncode5" />
 
-</LinearLayout>
+</androidx.constraintlayout.widget.ConstraintLayout>

Kotlin/demo/src/main/res/values/colors.xml

@@ -2,6 +2,8 @@
 <resources>
     <color name="colorPrimary">#29b6f6</color>
     <color name="colorPrimaryDark">#0086c3</color>
-    <color name="colorAccent">#444444</color>
+    <color name="colorAccent">#29b6f6</color>
+
+    <color name="textColor">#444</color>
 </resources>
 

Kotlin/demo/src/main/res/values/strings.xml

@@ -2,4 +2,11 @@
     <string name="app_name">BlurHash</string>
     <string name="hint_blurhash">BlurHash string</string>
     <string name="title_button_decode">Decode!</string>
+    <string name="title_button_encode1">Encode 1!</string>
+    <string name="title_button_encode2">Encode 2!</string>
+    <string name="title_button_encode3">Encode 3!</string>
+    <string name="title_button_encode4">Encode 4!</string>
+    <string name="title_button_encode5">Encode 5!</string>
+
+    <string name="demo_blurhash_string">LEHV6nWB2yk8pyo0adR*.7kCMdnj</string>
 </resources>

Kotlin/lib/build.gradle

@@ -1,6 +1,6 @@
 apply plugin: 'com.android.library'
-apply plugin: 'kotlin-android-extensions'
 apply plugin: 'kotlin-android'
+apply plugin: 'kotlin-android-extensions'
 
 android {
 

Kotlin/lib/src/main/java/com/wolt/blurhashkt/Base83.kt

@@ -0,0 +1,34 @@
+package com.wolt.blurhashkt
+
+internal object Base83 {
+
+    private val CHAR_MAP = listOf(
+            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
+            'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
+            'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
+            'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '#', '$', '%', '*', '+', ',',
+            '-', '.', ':', ';', '=', '?', '@', '[', ']', '^', '_', '{', '|', '}', '~'
+    )
+
+    fun encode(value: Int, length: Int, buffer: CharArray, offset: Int) {
+        var exp = 1
+        var i = 1
+        while (i <= length) {
+            val digit = (value / exp % 83)
+            buffer[offset + length - i] = CHAR_MAP[digit]
+            i++
+            exp *= 83
+        }
+    }
+
+    fun decode(str: String, from: Int = 0, to: Int = str.length): Int {
+        var result = 0
+        for (i in from until to) {
+            val index = CHAR_MAP.indexOf(str[i])
+            if (index != -1) {
+                result = result * 83 + index
+            }
+        }
+        return result
+    }
+}

Kotlin/lib/src/main/java/com/wolt/blurhashkt/BlurHashDecoder.kt

@@ -2,65 +2,46 @@ package com.wolt.blurhashkt
 
 import android.graphics.Bitmap
 import android.graphics.Color
+import com.wolt.blurhashkt.Utils.linearToSrgb
+import com.wolt.blurhashkt.Utils.signedPow2
+import com.wolt.blurhashkt.Utils.srgbToLinear
 import kotlin.math.PI
 import kotlin.math.cos
-import kotlin.math.pow
-import kotlin.math.withSign
 
 object BlurHashDecoder {
 
     fun decode(blurHash: String?, width: Int, height: Int, punch: Float = 1f): Bitmap? {
         if (blurHash == null || blurHash.length < 6) {
             return null
         }
-        val numCompEnc = decode83(blurHash, 0, 1)
+        val numCompEnc = Base83.decode(blurHash, 0, 1)
         val numCompX = (numCompEnc % 9) + 1
         val numCompY = (numCompEnc / 9) + 1
         if (blurHash.length != 4 + 2 * numCompX * numCompY) {
             return null
         }
-        val maxAcEnc = decode83(blurHash, 1, 2)
+        val maxAcEnc = Base83.decode(blurHash, 1, 2)
         val maxAc = (maxAcEnc + 1) / 166f
         val colors = Array(numCompX * numCompY) { i ->
             if (i == 0) {
-                val colorEnc = decode83(blurHash, 2, 6)
+                val colorEnc = Base83.decode(blurHash, 2, 6)
                 decodeDc(colorEnc)
             } else {
                 val from = 4 + i * 2
-                val colorEnc = decode83(blurHash, from, from + 2)
+                val colorEnc = Base83.decode(blurHash, from, from + 2)
                 decodeAc(colorEnc, maxAc * punch)
             }
         }
         return composeBitmap(width, height, numCompX, numCompY, colors)
     }
 
-    private fun decode83(str: String, from: Int = 0, to: Int = str.length): Int {
-        var result = 0
-        for (i in from until to) {
-            val index = charMap[str[i]] ?: -1
-            if (index != -1) {
-                result = result * 83 + index
-            }
-        }
-        return result
-    }
-
     private fun decodeDc(colorEnc: Int): FloatArray {
         val r = colorEnc shr 16
         val g = (colorEnc shr 8) and 255
         val b = colorEnc and 255
         return floatArrayOf(srgbToLinear(r), srgbToLinear(g), srgbToLinear(b))
     }
 
-    private fun srgbToLinear(colorEnc: Int): Float {
-        val v = colorEnc / 255f
-        return if (v <= 0.04045f) {
-            (v / 12.92f)
-        } else {
-            ((v + 0.055f) / 1.055f).pow(2.4f)
-        }
-    }
-
     private fun decodeAc(value: Int, maxAc: Float): FloatArray {
         val r = value / (19 * 19)
         val g = (value / 19) % 19
@@ -72,8 +53,6 @@ object BlurHashDecoder {
         )
     }
 
-    private fun signedPow2(value: Float) = value.pow(2f).withSign(value)
-
     private fun composeBitmap(
             width: Int, height: Int,
             numCompX: Int, numCompY: Int,
@@ -100,23 +79,4 @@ object BlurHashDecoder {
         return bitmap
     }
 
-    private fun linearToSrgb(value: Float): Int {
-        val v = value.coerceIn(0f, 1f)
-        return if (v <= 0.0031308f) {
-            (v * 12.92f * 255f + 0.5f).toInt()
-        } else {
-            ((1.055f * v.pow(1 / 2.4f) - 0.055f) * 255 + 0.5f).toInt()
-        }
-    }
-
-    private val charMap = listOf(
-            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
-            'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
-            'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
-            'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '#', '$', '%', '*', '+', ',',
-            '-', '.', ':', ';', '=', '?', '@', '[', ']', '^', '_', '{', '|', '}', '~'
-    )
-            .mapIndexed { i, c -> c to i }
-            .toMap()
-
 }