DrGraph原理示教 - OpenCV 4 功能 - 膨胀腐蚀

在二值图的结果基础上，可针对性处理。
这些处理有些是概念上的，有些是原理上的，也有形态上的，那就看用途与目的了。
本质上还是对二值图的黑白点进行处理，以用于图像增强、边缘检测、图像分割等多个领域。比如膨胀与腐蚀。
膨胀：输入图像与结构元素进行卷积计算，取局部极大值来替代中心值，可以使相互分离的物体连接起来。
腐蚀：取局部极小值替换中心值，可以断开两个连接在一起的物体。
这个概念对于没太多理论支持的程序员来说，术语太多，可以简单理解就是，膨胀与腐蚀是相对于白色区域而言的。如果膨胀，白色区域就象面团发酵一样会胀大，但空间就那么大，可能两个面团就会挨上合并成一个面团了。如果腐蚀，就象拉面，原来一根面条，可能就断成两根，当然断的地方肯定是从细处断。
原理很简单，代码也很简单，膨胀与腐蚀分别对应两个函数：dilate与erode，这两个函数的参数都一样。

/** @brief Erodes an image by using a specific structuring element.

The function erodes the source image using the specified structuring element that determines the
shape of a pixel neighborhood over which the minimum is taken:

\f[\texttt{dst} (x,y) =  \min _{(x',y'):  \, \texttt{element} (x',y') \ne0 } \texttt{src} (x+x',y+y')\f]

The function supports the in-place mode. Erosion can be applied several ( iterations ) times. In
case of multi-channel images, each channel is processed independently.

@param src input image; the number of channels can be arbitrary, but the depth should be one of
CV_8U, CV_16U, CV_16S, CV_32F or CV_64F.
@param dst output image of the same size and type as src.
@param kernel structuring element used for erosion; if `element=Mat()`, a `3 x 3` rectangular
structuring element is used. Kernel can be created using #getStructuringElement.
@param anchor position of the anchor within the element; default value (-1, -1) means that the
anchor is at the element center.
@param iterations number of times erosion is applied.
@param borderType pixel extrapolation method, see #BorderTypes. #BORDER_WRAP is not supported.
@param borderValue border value in case of a constant border
@sa  dilate, morphologyEx, getStructuringElement
 */
CV_EXPORTS_W void erode( InputArray src, OutputArray dst, InputArray kernel,
                         Point anchor = Point(-1,-1), int iterations = 1,
                         int borderType = BORDER_CONSTANT,
                         const Scalar& borderValue = morphologyDefaultBorderValue() );

/** @brief Dilates an image by using a specific structuring element.

The function dilates the source image using the specified structuring element that determines the
shape of a pixel neighborhood over which the maximum is taken:
\f[\texttt{dst} (x,y) =  \max _{(x',y'):  \, \texttt{element} (x',y') \ne0 } \texttt{src} (x+x',y+y')\f]

The function supports the in-place mode. Dilation can be applied several ( iterations ) times. In
case of multi-channel images, each channel is processed independently.

@param src input image; the number of channels can be arbitrary, but the depth should be one of
CV_8U, CV_16U, CV_16S, CV_32F or CV_64F.
@param dst output image of the same size and type as src.
@param kernel structuring element used for dilation; if elemenat=Mat(), a 3 x 3 rectangular
structuring element is used. Kernel can be created using #getStructuringElement
@param anchor position of the anchor within the element; default value (-1, -1) means that the
anchor is at the element center.
@param iterations number of times dilation is applied.
@param borderType pixel extrapolation method, see #BorderTypes. #BORDER_WRAP is not suported.
@param borderValue border value in case of a constant border
@sa  erode, morphologyEx, getStructuringElement
 */
CV_EXPORTS_W void dilate( InputArray src, OutputArray dst, InputArray kernel,
                          Point anchor = Point(-1,-1), int iterations = 1,
                          int borderType = BORDER_CONSTANT,
                          const Scalar& borderValue = morphologyDefaultBorderValue() );

其中，各参数含义如下：
src：输入图像。
kernel：用于腐蚀运算的核结构。
dst：输出图像（返回值）。
anchor：瞄点位置，默认是kernel对应区域的中心位置。
iterations：应用腐蚀操作迭代的次数。
borderType：边界模式，由BorderTypes定义。
borderValue：当边界模式为BORDER_CONSTANT时的边界像素值。

调试过程中，突然发现，膨胀腐蚀的输入也支持多通道图像，即不局限于灰度图

其中好坏利弊，那就看程序员自己体会了。