C++ OpenCV 类型 CV_32F 和 CV_32FC1 的区别
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Difference between OpenCV type CV_32F and CV_32FC1
提问by mlnthr
I would like to know if there is any difference between OpenCV types CV_32F and CV_32FC1? I already know that 32F stands for a "32bits floating point" and C1 for "single channel", but further explanations would be appreciated.
我想知道 OpenCV 类型 CV_32F 和 CV_32FC1 之间是否有任何区别？我已经知道 32F 代表“32 位浮点”，C1 代表“单通道”，但进一步的解释将不胜感激。
If yes, how are they different / which one should I use in which specific cases? As you might know that openCV types can get very tricky...
如果是，它们有什么不同/我应该在哪些特定情况下使用哪个？您可能知道 openCV 类型会变得非常棘手......
Thank you all in advance for your help!
在此先感谢大家的帮助！
回答by Miki
The value for both CV_32Fand CV_32FC1is 5(see explanation below), so numerically there is no difference.
两者的值CV_32F和CV_32FC1被5（见下面的说明），所以数值没有差别。
However:
然而：
CV_32Fdefines the depth of each element of the matrix, whileCV_32FC1defines both the depth of each element and the number of channels.
CV_32F定义矩阵的每个元素的深度，而CV_32FC1定义每个元素的深度和通道数。
A few examples...
几个例子...
Many functions, e.g. Sobelor convertTo, require the destination depth (and notthe number of channels), so you do:
许多函数，例如Sobel或convertTo，需要目标深度（而不是通道数），因此您可以：
Sobel(src, dst, CV_32F, 1, 0);
src.convertTo(dst, CV_32F);
But, when creating a matrix for example, you must also specify the number of channels, so:
但是，例如在创建矩阵时，您还必须指定通道数，因此：
Mat m(rows, cols, CV_32FC1);
Basically, every time you should also specify the number of channels, use CV_32FCx. If you just need the depth, use CV_32F
基本上，每次您还应该指定通道数时，请使用CV_32FCx. 如果您只需要深度，请使用CV_32F
CV_32Fis defined as:
CV_32F定义为：
#define CV_32F 5
while CV_32FC1is defined as:
而CV_32FC1定义为：
#define CV_CN_SHIFT 3
#define CV_DEPTH_MAX (1 << CV_CN_SHIFT)
#define CV_MAT_DEPTH_MASK (CV_DEPTH_MAX - 1)
#define CV_MAT_DEPTH(flags) ((flags) & CV_MAT_DEPTH_MASK)
#define CV_MAKETYPE(depth,cn) (CV_MAT_DEPTH(depth) + (((cn)-1) << CV_CN_SHIFT))
#define CV_32FC1 CV_MAKETYPE(CV_32F,1)
which evaluates to 5.
其评估为5.
You can check this with:
您可以通过以下方式检查：
#include <opencv2\opencv.hpp>
#include <iostream>
int main()
{
std::cout << CV_32F << std::endl;
std::cout << CV_32FC1 << std::endl;
return 0;
}
