add FloodFill.js

Recursive/FloodFill.js

@@ -0,0 +1,180 @@
+/**
+ * Flood fill, also called seed fill, is an algorithm that determines and alters the area connected
+ * to a given node in a multi-dimensional array with some matching attribute. It is used in the
+ * "bucket" fill tool of paint programs to fill connected, similarly-colored areas with a different
+ * color. (description adapted from https://en.wikipedia.org/wiki/Flood_fill) (see also:
+ * https://www.techiedelight.com/flood-fill-algorithm/).
+ */
+
+const neighbors = [[-1, -1], [-1, 0], [-1, 1], [0, -1], [0, 1], [1, -1], [1, 0], [1, 1]]
+
+const black = [0, 0, 0]
+const green = [0, 255, 0]
+const violet = [255, 0, 255]
+const white = [255, 255, 255]
+const orange = [255, 128, 0] // eslint-disable-line
+
+/*
+Doctests
+> testBreadthFirst([1, 1], green, orange, [1, 1]);
+orange
+> testBreadthFirst([1, 1], green, orange, [0, 1]);
+violet
+> testBreadthFirst([1, 1], green, orange, [6, 4]);
+white
+> testDepthFirst([1, 1], green, orange, [1, 1]);
+orange
+> testDepthFirst([1, 1], green, orange, [0, 1]);
+violet
+> testDepthFirst([1, 1], green, orange, [6, 4]);
+white
+*/
+
+/**
+* Implements the flood fill algorithm through a breadth-first approach using a queue.
+*
+* @param rgbData The image to which the algorithm is applied.
+* @param location The start location on the image.
+* @param targetColor The old color to be replaced.
+* @param replacementColor The new color to replace the old one.
+*/
+function breadthFirstSearch (rgbData, location, targetColor, replacementColor) {
+  if (location[0] < 0 ||
+    location[0] >= rgbData.length ||
+    location[1] < 0 ||
+    location[1] >= rgbData[0].length) {
+    throw new Error('location should point to a pixel within the rgbData')
+  }
+
+  const queue = []
+  queue.push(location)
+
+  while (queue.length > 0) {
+    breadthFirstFill(rgbData, location, targetColor, replacementColor, queue)
+  }
+}
+
+/**
+* Implements the flood fill algorithm through a depth-first approach using recursion.
+*
+* @param rgbData The image to which the algorithm is applied.
+* @param location The start location on the image.
+* @param targetColor The old color to be replaced.
+* @param replacementColor The new color to replace the old one.
+*/
+function depthFirstSearch (rgbData, location, targetColor, replacementColor) {
+  if (location[0] < 0 ||
+    location[0] >= rgbData.length ||
+    location[1] < 0 ||
+    location[1] >= rgbData[0].length) {
+    throw new Error('location should point to a pixel within the rgbData')
+  }
+
+  depthFirstFill(rgbData, location, targetColor, replacementColor)
+}
+
+/**
+* Utility-function to implement the breadth-first loop
+*
+* @param rgbData The image to which the algorithm is applied.
+* @param location The start location on the image.
+* @param targetColor The old color to be replaced.
+* @param replacementColor The new color to replace the old one.
+* @param queue The locations that still need to be visited.
+*/
+function breadthFirstFill (rgbData, location, targetColor, replacementColor, queue) {
+  const currentLocation = queue[0]
+  queue.shift()
+
+  if (rgbData[currentLocation[0]][currentLocation[1]] === targetColor) {
+    rgbData[currentLocation[0]][currentLocation[1]] = replacementColor
+
+    for (let i = 0; i < neighbors.length; i++) {
+      const x = currentLocation[0] + neighbors[i][0]
+      const y = currentLocation[1] + neighbors[i][1]
+      if (x >= 0 && x < rgbData.length && y >= 0 && y < rgbData[0].length) {
+        queue.push([x, y])
+      }
+    }
+  }
+}
+
+/**
+* Utility-function to implement the depth-first loop
+*
+* @param rgbData The image to which the algorithm is applied.
+* @param location The start location on the image.
+* @param targetColor The old color to be replaced.
+* @param replacementColor The new color to replace the old one.
+*/
+function depthFirstFill (rgbData, location, targetColor, replacementColor) {
+  if (rgbData[location[0]][location[1]] === targetColor) {
+    rgbData[location[0]][location[1]] = replacementColor
+
+    for (let i = 0; i < neighbors.length; i++) {
+      const x = location[0] + neighbors[i][0]
+      const y = location[1] + neighbors[i][1]
+      if (x >= 0 && x < rgbData.length && y >= 0 && y < rgbData[0].length) {
+        depthFirstFill(rgbData, [x, y], targetColor, replacementColor)
+      }
+    }
+  }
+}
+
+/**
+* Generates the rgbData-matrix for the tests
+*
+* @return example rgbData-matrix
+*/
+function generateTestRgbData () {
+  const layout = [
+    [violet, violet, green, green, black, green, green],
+    [violet, green, green, black, green, green, green],
+    [green, green, green, black, green, green, green],
+    [black, black, green, black, white, white, green],
+    [violet, violet, black, violet, violet, white, white],
+    [green, green, green, violet, violet, violet, violet],
+    [violet, violet, violet, violet, violet, violet, violet]
+  ]
+
+  // transpose layout-matrix so the x-index comes before the y-index
+  const transposed = []
+  for (let x = 0; x < layout[0].length; x++) {
+    transposed[x] = []
+    for (let y = 0; y < layout.length; y++) {
+      transposed[x][y] = layout[y][x]
+    }
+  }
+
+  return transposed
+}
+
+/**
+* Utility-function to test the function "breadthFirstSearch"
+*
+* @param fillLocation The start location on the image where the flood fill is applied.
+* @param targetColor The old color to be replaced.
+* @param replacementColor The new color to replace the old one.
+* @param testLocation The location of the color to be checked.
+* @return The color at testLocation
+*/
+function testBreadthFirst (fillLocation, targetColor, replacementColor, testLocation) {// eslint-disable-line
+  const rgbData = generateTestRgbData()
+  breadthFirstSearch(rgbData, fillLocation, targetColor, replacementColor)
+  return rgbData[testLocation[0]][testLocation[1]]
+}
+
+/**
+* Utility-function to test the function "depthFirstSearch"
+*
+* @param fillLocation The start location on the image where the flood fill is applied.
+* @param targetColor The old color to be replaced.
+* @param replacementColor The new color to replace the old one.
+* @param testLocation The location of the color to be checked.
+* @return The color at testLocation
+*/
+function testDepthFirst (fillLocation, targetColor, replacementColor, testLocation) {// eslint-disable-line
+  const rgbData = generateTestRgbData()
+  depthFirstSearch(rgbData, fillLocation, targetColor, replacementColor)
+  return rgbData[testLocation[0]][testLocation[1]]
+}