FloodFill [Flood Fill算法]
# 介绍
Flood fill 算法是从一个区域中提取若干个连通的点与其他相邻区域区分开（或分别染成不同颜色）的经典算法。因为其思路类似洪水从一个区域扩散到所有能到达的区域而得名。
# 原理
Flood fill 算法接受三个参数：起始节点，目标颜色和替换颜色。算法遍历所有的节点以寻找和起始节点相连的节点（通过一条目标颜色的路径相连），然后 改变他们的颜色为替换颜色。目前有许多 flood-fill 算法的构建方式，但是他们都显示或隐式的使用队列或者栈。根据我们是否考虑当前节点对角线方向的节点，算法分为四路算法（不考虑对角线方向的节点）和八路算法（考虑对角线方向的节点）。
四路算法：
八路算法：
# 视频
# 实现
# JavaScript
/**
* Flood fill.
*
* 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 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]]
/**
* 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.
*/
export 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.
*/
export 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)
}
}
}
}
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# 参考
编辑 (opens new window)
上次更新: 2022/10/17, 12:47:34