From 551c0bd0c3acd161f6d25154ff49762fd92f412f Mon Sep 17 00:00:00 2001
From: Jakub Brzegowski <symfiz@gmail.com>
Date: Mon, 23 Mar 2020 14:22:20 +0100
Subject: [PATCH] Add solution to scalashop

---
 .../scala/scalashop/HorizontalBoxBlur.scala   | 14 +++++++----
 .../scala/scalashop/VerticalBoxBlur.scala     | 15 ++++++++----
 .../src/main/scala/scalashop/package.scala    | 23 +++++++++++++++++--
 3 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/scalashop/src/main/scala/scalashop/HorizontalBoxBlur.scala b/scalashop/src/main/scala/scalashop/HorizontalBoxBlur.scala
index f86b45c..4d733ff 100644
--- a/scalashop/src/main/scala/scalashop/HorizontalBoxBlur.scala
+++ b/scalashop/src/main/scala/scalashop/HorizontalBoxBlur.scala
@@ -40,8 +40,11 @@ object HorizontalBoxBlur extends HorizontalBoxBlurInterface {
    *  Within each row, `blur` traverses the pixels by going from left to right.
    */
   def blur(src: Img, dst: Img, from: Int, end: Int, radius: Int): Unit = {
-  // TODO implement this method using the `boxBlurKernel` method
-  ???
+    for (y <- from until end) {
+      for (x <- 0 until src.width) {
+        dst.update(x, y, boxBlurKernel(src, x, y, radius))
+      }
+    }
   }
 
   /** Blurs the rows of the source image in parallel using `numTasks` tasks.
@@ -51,9 +54,12 @@ object HorizontalBoxBlur extends HorizontalBoxBlurInterface {
    *  rows.
    */
   def parBlur(src: Img, dst: Img, numTasks: Int, radius: Int): Unit = {
-  // TODO implement using the `task` construct and the `blur` method
+    val perTask: Int = Math.max(1, src.height / numTasks)
+    val froms = (0 until src.height by perTask).toList
+    val blurRanges = froms.zip(froms.tail :+ src.height)
+    val tasks = blurRanges.map({ case (from, end) => task { blur(src, dst, from, end, radius) }})
 
-  ???
+    tasks.foreach(task => task.join())
   }
 
 }
diff --git a/scalashop/src/main/scala/scalashop/VerticalBoxBlur.scala b/scalashop/src/main/scala/scalashop/VerticalBoxBlur.scala
index f406e40..213aeeb 100644
--- a/scalashop/src/main/scala/scalashop/VerticalBoxBlur.scala
+++ b/scalashop/src/main/scala/scalashop/VerticalBoxBlur.scala
@@ -42,8 +42,11 @@ object VerticalBoxBlur extends VerticalBoxBlurInterface {
    *  bottom.
    */
   def blur(src: Img, dst: Img, from: Int, end: Int, radius: Int): Unit = {
-    // TODO implement this method using the `boxBlurKernel` method
-    ???
+    for (x <- from until end) {
+      for (y <- 0 until src.height) {
+        dst.update(x, y, boxBlurKernel(src, x, y, radius))
+      }
+    }
   }
 
   /** Blurs the columns of the source image in parallel using `numTasks` tasks.
@@ -53,8 +56,12 @@ object VerticalBoxBlur extends VerticalBoxBlurInterface {
    *  columns.
    */
   def parBlur(src: Img, dst: Img, numTasks: Int, radius: Int): Unit = {
-    // TODO implement using the `task` construct and the `blur` method
-    ???
+    val perTask: Int = Math.max(1, src.width / numTasks)
+    val froms = (0 until src.width by perTask).toList
+    val blurRanges = froms.zip(froms.tail :+ src.width)
+    val tasks = blurRanges.map({ case (from, end) => task { blur(src, dst, from, end, radius) }})
+
+    tasks.foreach(task => task.join())
   }
 
 }
diff --git a/scalashop/src/main/scala/scalashop/package.scala b/scalashop/src/main/scala/scalashop/package.scala
index ae29e42..f56a115 100644
--- a/scalashop/src/main/scala/scalashop/package.scala
+++ b/scalashop/src/main/scala/scalashop/package.scala
@@ -41,9 +41,28 @@ package object scalashop extends BoxBlurKernelInterface {
 
   /** Computes the blurred RGBA value of a single pixel of the input image. */
   def boxBlurKernel(src: Img, x: Int, y: Int, radius: Int): RGBA = {
+    val (x1, x2) = (clamp(x - radius, 0, src.width - 1), clamp(x + radius, 0, src.width - 1))
+    val (y1, y2) = (clamp(y - radius, 0, src.height - 1), clamp(y + radius, 0, src.height - 1))
+    val pixelsCount = (x2 - x1 + 1) * (y2 - y1 + 1)
+    var i = x1
+    var j = 0
+    var r, g, b, a = 0
+
+    while (i <= x2) {
+      j = y1
+      while (j <= y2) {
+        val pixel = src(i, j)
+        r += red(pixel)
+        g += green(pixel)
+        b += blue(pixel)
+        a += alpha(pixel)
+
+        j += 1
+      }
+      i += 1
+    }
 
-    // TODO implement using while loops
-    ???
+    rgba(r / pixelsCount, g / pixelsCount, b / pixelsCount, a / pixelsCount)
   }
 
   val forkJoinPool = new ForkJoinPool