边界填充算法讲解_边界填充算法

边界填充算法讲解

Boundary fill is the algorithm used frequently in computer graphics to fill a desired color inside a closed polygon having the same boundary color for all of its sides.

边界填充是在计算机图形学中经常使用的算法，用于在其所有边都具有相同边界颜色的封闭多边形内填充所需颜色。

The most approached implementation of the algorithm is a stack-based recursive function.

该算法最接近的实现是基于堆栈的递归函数。

这个怎么运作： (How it works:)

The problem is pretty simple and usually follows these steps:

该问题非常简单，通常按照以下步骤操作：

Take the position of the starting point and the boundary color.取起点的位置和边界颜色。
Decide wether you want to go in 4 directions (N, S, W, E) or 8 directions (N, S, W, E, NW, NE, SW, SE).确定您要沿4个方向(N，S，W，E)还是8个方向(N，S，W，E，NW，NE，SW，SE)行驶。
Choose a fill color.选择一种填充颜色。
Travel in those directions.朝那些方向旅行。
If the pixel you land on is not the fill color or the boundary color , replace it with the fill color.如果您着陆的像素不是填充颜色或边界颜色，则将其替换为填充颜色。

Repeat 4 and 5 until you’ve been everywhere within the boundaries.

重复4和5，直到到达边界内的任何地方。

某些限制： (Certain Restrictions:)

The boundary color should be the same for all the edges of the polygon.

多边形的所有边缘的边界颜色应相同。

The starting point should be within the polygon.

起点应在多边形内。

代码段： (Code Snippet:)

void boundary_fill(int pos_x, int pos_y, int boundary_color, int fill_color)
{
current_color= getpixel(pos_x,pos_y);  //get the color of the current pixel position
if( current_color!= boundary_color || currrent_color != fill_color) // if pixel not already filled or part of the boundary then
{    putpixel(pos_x,pos_y,fill_color);  //change the color for this pixel to the desired fill_colorboundary_fill(pos_x + 1, pos_y,boundary_color,fill_color);  // perform same function for the east pixelboundary_fill(pos_x - 1, pos_y,boundary_color,fill_color);  // perform same function for the west pixelboundary_fill(pos_x, pos_y + 1,boundary_color,fill_color);  // perform same function for the north pixelboundary_fill(pos_x, pos_y - 1,boundary_color,fill_color);  // perform same function for the south pixel
}
}

From the given code you can see that for any pixel that you land on, you first check whether it can be changed to the fill_color and then you do so for its neighbours till all the pixels within the boundary have been checked.

从给定的代码中可以看到，对于您着陆的任何像素，首先要检查是否可以将其更改为fill_color，然后对其相邻像素进行更改，直到检查了边界内的所有像素为止。

翻译自: https://www.freecodecamp.org/news/boundary-fill-algorithm/

边界填充算法讲解