opencv - OpenCV,我们如何将 Mat min 标准化为 max 并将 max 标准化为 min?
问题描述
我想将 a 标准化Mat
为最小值为 255 和最大值为 0 (标准化0~255Mat
之间的值)。
例如,如果我们有一个像[0.02, 0.002, 0.0002]
标准化后的数组,我想得到这样的结果:[3, 26, 255]
,但现在当我使用时,NORM_MINMAX
我得到了[255, 26, 3]
。
但是我没有找到任何函数来做NORM_MINMAX
.
使用的代码:
cv::Mat mat(10, 10, CV_64F);
mat.setTo(0);
mat.row(0) = 0.02;
mat.row(1) = 0.002;
mat.row(2) = 0.0002;
cv::normalize(mat, mat, 255, 0, cv::NORM_MINMAX);
mat.convertTo(mat, CV_8UC1);
std::cout << mat << std::endl;
结果是:
[255, 255, 255, 255, 255, 255, 255, 255, 255, 255;
26, 26, 26, 26, 26, 26, 26, 26, 26, 26;
3, 3, 3, 3, 3, 3, 3, 3, 3, 3;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
但我想要上述结果的倒数。
更新:当我从垫子中减去 255 时:
cv::subtract(255, mat, mat, mat); // the last mat acts as mask
std::cout << mat << std::endl;
结果是:
[ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
229, 229, 229, 229, 229, 229, 229, 229, 229, 229;
252, 252, 252, 252, 252, 252, 252, 252, 252, 252;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
解决方案
我终于找到了如何计算的方法,以下是步骤:
通过使用反比例公式,我们可以很容易地计算出NORM_MINMAX
x = a*b/c
其中a = mat 元素的最小值,b =255(最大值),c = 我们要计算它的元素。
cv::Mat mat(10, 10, CV_64F);
mat.setTo(0);
mat.row(0) = 0.02;
mat.row(1) = 0.002;
mat.row(2) = 0.0002;
std::cout << mat<< std::endl;
// craete a mask
cv::Mat mask(mat.size(), CV_8U);
mask.setTo(0);
mask.row(0) = 255;
mask.row(1) = 255;
mask.row(2) = 255;
// find the min value
double min;
cv::minMaxLoc(mat, &min, nullptr, nullptr, nullptr, mask);
std::cout << "min=" << min << std::endl;
// unfortunately opencv divide operation does not support mask, so we need some extra steps to perform.
cv::Mat result, maskNeg;
cv::divide(min*255, mat, result); // this is the magic line
cv::bitwise_not(mask, maskNeg);
mat.copyTo(result, maskNeg);
std::cout << result << std::endl;
// convert to 8bit
result .convertTo(result , CV_8UC1);
std::cout << "the final result:" << std::endl;
std::cout << temp << std::endl;
和输出:
original mat
[0.02, 0.02, 0.02, 0.02, 0.02, 0.02, 0.02, 0.02, 0.02, 0.02;
0.002, 0.002, 0.002, 0.002, 0.002, 0.002, 0.002, 0.002, 0.002, 0.002;
0.0002, 0.0002, 0.0002, 0.0002, 0.0002, 0.0002, 0.0002, 0.0002, 0.0002, 0.0002;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
min=0.0002
the calculated min-max
[2.55, 2.55, 2.55, 2.55, 2.55, 2.55, 2.55, 2.55, 2.55, 2.55;
25.5, 25.5, 25.5, 25.5, 25.5, 25.5, 25.5, 25.5, 25.5, 25.5;
255, 255, 255, 255, 255, 255, 255, 255, 255, 255;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
the final result:
[ 3, 3, 3, 3, 3, 3, 3, 3, 3, 3;
26, 26, 26, 26, 26, 26, 26, 26, 26, 26;
255, 255, 255, 255, 255, 255, 255, 255, 255, 255;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0;
0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
是的,这就是我想要的。
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