OpenCV图像旋转,指定填充背景颜色边界颜色

蔚落 2022-06-08 05:14 484阅读 0赞

# OpenCV图像旋转,指定填充背景颜色边界颜色 #

OpenCV与图像旋转有关的函数：

（1）warpAffine函数

void cv::warpAffine ( InputArray  src,     OutputArray  dst,     InputArray  M,     Size  dsize,     int  flags = INTER_LINEAR,     int  borderMode = BORDER_CONSTANT,     const Scalar &  borderValue = Scalar()    )     
      
       Applies an affine transformation to an image. The function warpAffine transforms the source image using the specified matrix: dst(x,y)=src(M11x+M12y+M13,M21x+M22y+M23) when the flag WARP_INVERSE_MAP is set. Otherwise, the transformation is first inverted with cv::invertAffineTransform and then put in the formula above instead of M. The function cannot operate in-place. Parameters src input image. dst output image that has the size dsize and the same type as src . M 2×3  transformation matrix. dsize size of the output image. flags combination of interpolation methods (see cv::InterpolationFlags) and the optional flag WARP_INVERSE_MAP that means that M is the inverse transformation (  dst→src  ). borderMode pixel extrapolation method (see cv::BorderTypes); when borderMode=BORDER_TRANSPARENT, it means that the pixels in the destination image corresponding to the "outliers" in the source image are not modified by the function. borderValue value used in case of a constant border; by default, it is 0.

中文解释：

C++: void warpAffine(InputArray src, OutputArray dst, InputArray M, Size dsize, int flags=INTER\_LINEAR, intborderMode=BORDER\_CONSTANT, const Scalar& borderValue=Scalar())  
  InputArray src：输入的图像C++: void warpAffine(InputArray src, OutputArray dst, InputArray M, Size dsize, int flags=INTER\_LINEAR, intborderMode=BORDER\_CONSTANT, const Scalar& borderValue=Scalar())  
  第1个参数：OutputArray dst：输出的图像   
  第2个参数：InputArray M：透视变换的矩阵  
  第3个参数：Size dsize：输出图像的大小  
  第4个参数：int flags=INTER\_LINEAR：输出图像的插值方法，可以为  
            INTER\_LINEAR 线性插值；  
            INTER\_NEAREST 最近邻插值；  
            INTER\_AREA 区域插值  
            INTER\_CUBIC 三次条样插值  
            CV\_WARP\_INVERSE\_MAP：指定 matrix 是输出图像到输入图像的反变换，因此可以直接用来做象素插值。否则, 函数从 map\_matrix 得到反变换。  
            CV\_WARP\_FILL\_OUTLIERS：填充所有缩小图像的象素。如果部分象素落在输入图像的边界外，那么它们的值设定为 fillval（fillval  
用来填充边界外面的值）.

第5个参数：int borderMode：图像边界的处理方式，默认是BORDER\_CONSTANT（即指定常数值填充） ，实质上，边界处理类型，该枚举型还有：

<table style="font-stretch: normal; font-size: 14px; line-height: 22px; font-family: Helvetica, &quot;Segoe UI&quot;, Arial, freesans, sans-serif; word-wrap: break-word; margin-bottom: 10px; border: 1px solid rgb(168, 184, 217); border-spacing: 0px; border-radius: 4px; box-shadow: rgba(0, 0, 0, 0.14902) 2px 2px 2px; color: rgb(0, 0, 0);"> 
 <tbody> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <th colspan="2" style="padding: 5px 7px 4px; background-image: url(&quot;nav_f.png&quot;); background-repeat: repeat-x; background-color: rgb(226, 232, 242); font-size: 12.6px; color: rgb(37, 53, 85); text-align: left; font-weight: 400; border-top-left-radius: 4px; border-top-right-radius: 4px; border-bottom: 1px solid rgb(168, 184, 217);">Enumerator</th> 
 </tr> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <td style="padding: 3px 7px 2px; white-space: nowrap; border-right: 1px solid rgb(168, 184, 217); border-bottom: 1px solid rgb(168, 184, 217); vertical-align: top;"><a style="color: rgb(61, 87, 140);" rel="nofollow"></a>BORDER_CONSTANT&nbsp;</td> 
 <td style="padding: 3px 7px 2px; border-bottom: 1px solid rgb(168, 184, 217);"><code style="font-stretch: normal; line-height: normal; font-family: Consolas, &quot;Liberation Mono&quot;, Courier, monospace; font-size: 12px; white-space: pre-wrap; padding: 0px; background-color: rgb(221, 221, 221); vertical-align: baseline;">iiiiii|abcdefgh|iiiiiii</code>&nbsp;with some specified&nbsp;<code style="font-stretch: normal; line-height: normal; font-family: Consolas, &quot;Liberation Mono&quot;, Courier, monospace; font-size: 12px; white-space: pre-wrap; padding: 0px; background-color: rgb(221, 221, 221); vertical-align: baseline;">i（指定常数填充）</code></td> 
 </tr> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <td style="padding: 3px 7px 2px; white-space: nowrap; border-right: 1px solid rgb(168, 184, 217); border-bottom: 1px solid rgb(168, 184, 217); vertical-align: top;"><a style="color: rgb(61, 87, 140);" rel="nofollow"></a>BORDER_REPLICATE&nbsp;</td> 
 <td style="padding: 3px 7px 2px; border-bottom: 1px solid rgb(168, 184, 217);"><code style="font-stretch: normal; line-height: normal; font-family: Consolas, &quot;Liberation Mono&quot;, Courier, monospace; font-size: 12px; white-space: pre-wrap; padding: 0px; background-color: rgb(221, 221, 221); vertical-align: baseline;">aaaaaa|abcdefgh|hhhhhhh（复制边缘像素填充）</code></td> 
 </tr> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <td style="padding: 3px 7px 2px; white-space: nowrap; border-right: 1px solid rgb(168, 184, 217); border-bottom: 1px solid rgb(168, 184, 217); vertical-align: top;"><a style="color: rgb(61, 87, 140);" rel="nofollow"></a>BORDER_REFLECT&nbsp;</td> 
 <td style="padding: 3px 7px 2px; border-bottom: 1px solid rgb(168, 184, 217);"><code style="font-stretch: normal; line-height: normal; font-family: Consolas, &quot;Liberation Mono&quot;, Courier, monospace; font-size: 12px; white-space: pre-wrap; padding: 0px; background-color: rgb(221, 221, 221); vertical-align: baseline;">fedcba|abcdefgh|hgfedcb（反射复制边界像素）</code></td> 
 </tr> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <td style="padding: 3px 7px 2px; white-space: nowrap; border-right: 1px solid rgb(168, 184, 217); border-bottom: 1px solid rgb(168, 184, 217); vertical-align: top;"><a style="color: rgb(61, 87, 140);" rel="nofollow"></a>BORDER_WRAP&nbsp;</td> 
 <td style="padding: 3px 7px 2px; border-bottom: 1px solid rgb(168, 184, 217);"><code style="font-stretch: normal; line-height: normal; font-family: Consolas, &quot;Liberation Mono&quot;, Courier, monospace; font-size: 12px; white-space: pre-wrap; padding: 0px; background-color: rgb(221, 221, 221); vertical-align: baseline;">cdefgh|abcdefgh|abcdefg</code></td> 
 </tr> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <td style="padding: 3px 7px 2px; white-space: nowrap; border-right: 1px solid rgb(168, 184, 217); border-bottom: 1px solid rgb(168, 184, 217); vertical-align: top;"><a style="color: rgb(61, 87, 140);" rel="nofollow"></a>BORDER_REFLECT_101&nbsp;</td> 
 <td style="padding: 3px 7px 2px; border-bottom: 1px solid rgb(168, 184, 217);"><code style="font-stretch: normal; line-height: normal; font-family: Consolas, &quot;Liberation Mono&quot;, Courier, monospace; font-size: 12px; white-space: pre-wrap; padding: 0px; background-color: rgb(221, 221, 221); vertical-align: baseline;">gfedcb|abcdefgh|gfedcba（对称填充，也就是以最边缘像素为轴）</code></td> 
 </tr> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <td style="padding: 3px 7px 2px; white-space: nowrap; border-right: 1px solid rgb(168, 184, 217); border-bottom: 1px solid rgb(168, 184, 217); vertical-align: top;"><a style="color: rgb(61, 87, 140);" rel="nofollow"></a>BORDER_TRANSPARENT&nbsp;</td> 
 <td style="padding: 3px 7px 2px; border-bottom: 1px solid rgb(168, 184, 217);"><code style="font-stretch: normal; line-height: normal; font-family: Consolas, &quot;Liberation Mono&quot;, Courier, monospace; font-size: 12px; white-space: pre-wrap; padding: 0px; background-color: rgb(221, 221, 221); vertical-align: baseline;">uvwxyz|absdefgh|ijklmno</code></td> 
 </tr> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <td style="padding: 3px 7px 2px; white-space: nowrap; border-right: 1px solid rgb(168, 184, 217); border-bottom: 1px solid rgb(168, 184, 217); vertical-align: top;"><a style="color: rgb(61, 87, 140);" rel="nofollow"></a>BORDER_REFLECT101&nbsp;</td> 
 <td style="padding: 3px 7px 2px; border-bottom: 1px solid rgb(168, 184, 217);">same as BORDER_REFLECT_101</td> 
 </tr> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <td style="padding: 3px 7px 2px; white-space: nowrap; border-right: 1px solid rgb(168, 184, 217); border-bottom: 1px solid rgb(168, 184, 217); vertical-align: top;"><a style="color: rgb(61, 87, 140);" rel="nofollow"></a>BORDER_DEFAULT&nbsp;</td> 
 <td style="padding: 3px 7px 2px; border-bottom: 1px solid rgb(168, 184, 217);">same as BORDER_REFLECT_101</td> 
 </tr> 
 <tr style="transition-property: background-color, box-shadow; transition-duration: 0.5s;"> 
 <td style="padding: 3px 7px 2px; white-space: nowrap; border-right: 1px solid rgb(168, 184, 217); border-bottom: none; vertical-align: top;"><a style="color: rgb(61, 87, 140);" rel="nofollow"></a>BORDER_ISOLATED&nbsp;</td> 
 <td style="padding: 3px 7px 2px; border-bottom: none;">do not look outside of ROI</td> 
 </tr> 
 </tbody> 
</table>

第6个参数：const Scalar& borderValue=Scalar()：边界的颜色设置，一般默认是0。

（2）getRotationMatrix2D函数
        Mat getRotationMatrix2D(Point2f center, double angle, double scale)
    参数详解：
      Point2f center：表示旋转的中心点
      double angle：表示旋转的角度
      double scale：图像缩放因子

例子：

int main() {
    	Mat src = imread("D:\\OpencvTest\\test1.jpg");
    	cv::Mat dst;
    	//float scale = 200.0/ src.rows;//缩放因子  
    	//cv::resize(src, src, cv::Size(), scale, scale, cv::INTER_LINEAR);  
    	//旋转角度-20度    
    	double angle = -20;
    	//输出图像的尺寸与原图一样  
    	cv::Size dst_sz(src.cols, src.rows);
    
    	//指定旋转中心    
    	cv::Point2f center(src.cols / 2., src.rows / 2.);
    
    	//获取旋转矩阵（2x3矩阵）    
    	cv::Mat rot_mat = cv::getRotationMatrix2D(center, angle, 1.0);
    	//设置选择背景边界颜色：绿色  
    	cv::Scalar borderColor = Scalar(0, 238, 0);
    	cv::warpAffine(src, dst, rot_mat, src.size(), INTER_LINEAR, BORDER_CONSTANT, borderColor);  
    	//cv::warpAffine(src, dst, rot_mat, dst_sz, INTER_LINEAR, BORDER_REPLICATE);
    
    	//显示旋转效果    
    	cv::imshow("src image ", src);
    	cv::imshow("Rotation Image", dst);
    	waitKey(0);
    	return 0;
    	return 0;
    }

运行效果： 
     改为BORDER_REPLICATE：复制边缘填充，其效果如下： cv::warpAffine(src, dst, rot_mat, dst_sz, INTER_LINEAR, BORDER_REPLICATE);
    
    
     【尊重原创，转载请注明出处】 http://blog.csdn.net/guyuealian/article/details/77993410