将节点数组(可变长度）转换为常量浮点**以调用opencv.calcHist

Convert Node Array (variable lenght) to a const float** to call opencv.calcHist

本文关键字：常量 calcHist opencv 调用 转换 数组 节点      更新时间：2023-10-16

>上下文

我目前正在研究 https://github.com/piercus/node-opencv(从 https://github.com/peterbraden/node-opencv 分叉(，我正在为 calcHist 函数实现一个绑定器。

问题

  • C++函数将const float** ranges作为输入 (见 http://docs.opencv.org/2.4/modules/imgproc/doc/histograms.html#calchist(
  • 我想设置输入的大小，考虑到
  • 我不知道如何在不破坏编译器的情况下有条件地设置此const float**的大小

解决方法

考虑到最大尺寸数为 3，我做了一个解决方法(请参阅完整源代码 )

// Wrap Javascript input which is like [[0, 256], [0, 256]]
Local<Array> nodeRanges = Local<Array>::Cast(info[3]->ToObject());
// create a first table
float histRanges[dims][2];
for (unsigned int i = 0; i < dims; i++) {
Local<Array> nodeRange = Local<Array>::Cast(nodeRanges->Get(i)->ToObject());
float lower = nodeRange->Get(0)->NumberValue();
float higher = nodeRange->Get(1)->NumberValue();
histRanges[i][0] = lower;
histRanges[i][1] = higher;
}
// minimum length is 1 so i can fullfill first range without issue
float first_range[] = { histRanges[0][0], histRanges[0][1] };
float second_range[] = { 0, 0}; // here is my problem, do i really need to do this
float third_range[] = { 0, 0};// same problem here
if(dims >= 2){
second_range[0] = histRanges[1][0];
second_range[1] = histRanges[1][1];
}
if(dims >= 3){
third_range[0] = histRanges[2][0];
third_range[1] = histRanges[2][1];
}
// now i can create a const float** compatible type 
const float* histRanges1[] = {first_range, second_range, third_range};
[... other stuffs ...]
// const float** is needed here
cv::calcHist(&inputImage, 1, channels, cv::Mat(), outputHist, dims, histSize, histRanges1, uniform);

问题

是否可以在不创建"零填充"对象的情况下以优雅的方式做到这一点？ 我希望输入的最大大小为 32(而不是 3(。

你不需要复制histRanges的内容，因为其中的数字已经布置为float数组，就像cv::calcHist要求的那样。您只需要创建一个指向这些数组的指针数组。

float histRanges[dims][2];
const float* ranges[dims];
for (unsigned int i = 0; i < dims; i++) {
Local<Array> nodeRange = Local<Array>::Cast(nodeRanges->Get(i)->ToObject());
float lower = nodeRange->Get(0)->NumberValue();
float higher = nodeRange->Get(1)->NumberValue();
histRanges[i][0] = lower;
histRanges[i][1] = higher;
ranges[i] = histRanges[i];
}
cv::calcHist(&inputImage, 1, channels, cv::Mat(), outputHist, dims, histSize, ranges, uniform);
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