I want to get all distances (confidence) from predict function so I decided to change the function but my program still uses the default function (I think it reads from dlls and libs)
so how can I change a function ? Should I use cmake ? If yes how ? Please help me
Since OpenCV doesn't provide a default function, you have to create your own by creating a vector which has distance and label. You can write your own function as below and store the distance and label in the vector. Here you need to rebuild the opencv.
virtual void predict(InputArray src, int &label, double &confidence, Vector <variable>) const = 0;
Related
I used metal to do some interpolation task. I wrote the kernel function as followed:
kernel void kf_interpolation( device short *dst, device uchar *src, uint id [[ thread_position_in_grid ]] )
{
dst[id] = src[id-1] + src[id] + src[id+1];
}
That kernel function could not gave expected value. And I found the cause was that the src[id-1] was always 0, which was false value. However, src[id+1] contained the right value. The question is how could I use the neighbour unit correctly, e.g. [id-1], in kernel functions. Thanks in advance.
The most efficient way to handle edge cases like this is usually to grow your source array at each end and offset the indices. So for N calculations, allocate your src array with N+2 elements, fill elements 1 through N (inclusive) with the source data, and set element 0 and N+1 to whatever you want the edge condition to be.
An even more efficient method would be to use MTLTextures instead of MTLBuffers. MTLTextures have an addressing mode attached to them which causes the hardware to automatically substitute either zero or the nearest valid texel when you read off the edge of a texture. They can also do linear interpolation in hardware for free, which can be of great help for resampling, assuming bilinear interpolation is good enough for you. If not, I recommend looking at MPSImageLanczosScale as an alternative.
You can make a MTLTexture from a MTLBuffer. The two will alias the same pixel data.
I have no idea for how to implement matrix implementation efficiently in OpenCV.
I have binary Mat nz(150,600) with 0 and 1 elements.
I have Mat mk(150,600) with double values.
I like to implement as in Matlab as
sk = mk(nz);
That command copy mk to sk only for those element of mk element at the location where nz has 1. Then make sk into a row matrix.
How can I implement it in OpenCV efficiently for speed and memory?
You should take a look at Mat::copyTo and Mat::clone.
copyTo will make an copy with optional mask where its non-zero elements indicate which matrix elements need to be copied.
mk.copyTo(sk, nz);
And if you really want a row matrix then call sk.reshape() as member sansuiso already suggested. This method ...
creates alternative matrix header for the same data, with different
number of channels and/or different number of rows.
bkausbk gave the best answer. However, a second way around:
A=bitwise_and(nz,mk);
If you access A, you can copy the non-zero into a std::vector. If you want your output to be a cv::Mat instance then you have to allocate the memory first:
S=countNonZero(A); //size of the final output matrix
Now, fast element access is an actual topic of itself. Google it. Or have a look at opencv/modules/core/src/stat.cpp where countNonZero() is implemented to get some ideas.
There are two steps involved in your task.
First, you convert to double the input matrix:
cv::Mat binaryMat; // source matrix, filled somewhere
cv::Mat doubleMat; // target matrix (with doubles)
binaryMat.convertTo(doubleMat, CV64F); // Perform the conversion
Then, reshape the result as a row matrix:
doubleMat = cv::reshape(doubleMat, 1, 1);
// Alternatively:
cv::Mat doubleRow = cv::reshape(doubleMat, 1, 1);
The cv::reshape operation is efficient in the sense that the data is not copied, only the structure header changes.
This function returns a new reference to a matrix (by creating a new header), thus you should not forget to assign its result.
I tried to cv::bitwise_not to a cv::Mat matrix of double values. I applied like
cv::bitwise_not(img, imgtemp);
img is CV_64F data of 0 and 1. But imgtemp has all nonsense data inside.
I am expecting 0 in img to be 1 at imgtemp and 1 in img to be 0 at imgtemp. How to apply bitwise_not to a double Mat matrix?
Thanks
I cannot get the sense of doing a bitwise not of a double (floating point) value: you will be doing bitwise operations also on the exponent (see here). All bits will be inverted, from 0 to 1 and viceversa.
There is also a note on this aspect in the function documentation.
In case of a floating-point input array, its machine-specific bit
representation (usually IEEE754-compliant) is used for the operation.
If you want zeros to become ones and viceversa, as you suggested, you could do:
cv::threshold(warpmask, warpmaskTemp,0.5,1.0,THRESH_BINARY_INV)
(see documentation) (and yes, you can use same matrix for input and destination).
I think you are either getting the method signature wrong or wrongly named the parameters for the bitwise_not method.
According to [OpenCV 2.4.6 Documentation on bitwise_not() method] (http://docs.opencv.org/modules/core/doc/operations_on_arrays.html#void bitwise_not(InputArray src, OutputArray dst, InputArray mask))
void bitwise_not(InputArray src, OutputArray dst, InputArray mask=noArray())
If you are going to use any mask, it needs to be the last argument as mask is an optional for 'bitwise_not' method.
Additionally, all the data types need to be the same in order to avoid confusion. What I am trying to imply is that your source and destination data formats and any interim ones such as the method parameters must be in the same format. You cannot have on ein CV_64F and others in different. If I am not loosing my marbles here, bitwise operation would possibly require you to have all the data in unsigned or signed integer format for the sake of simplicity. Nevertheless, you should have all the types same.
About the garbage that you got, I think it is a general and good programming practice that you initialise your variables with some reasonable values. This helps when you are debugging step by step and ascertain the details where it failed.
Give it a try.
To follow on from Antonio's answer, you should use the right tool for the job. double is not an appropriate storage medium for boolean data.
In open cv you can type a boolean as an unsigned char (8bits). Although in typing your own true value you can pick any non-zero value, in open cv it is more natural to have 0/255; that way fitting in with open cv's bitwise operations and comparison operators. E.g. a bitwise not could be achieved by result = (input == 0) which can take any type. threshold in Antonio's answer maintains the same type (useful in some circumstances). For bitwise_not you should have it in the boolean format first.
Unfortunately opencv makes it very difficult to work with black and white bitwise data.
I need to modify some of the variables inside the dft function in OpenCV to make it suitable for my application.
Where can I find the dft source code?
I've tried C:\opencv243\build\include\opencv2\core.hpp but it only gives me the description of dft:
//! performs forward or inverse 1D or 2D Discrete Fourier Transformation
CV_EXPORTS_W void dft(InputArray src, OutputArray dst, int flags=0, int nonzeroRows=0);
What is the procedure after source code modification? Do I have to give it a different name such as dft2()?
Where to save the new function?
I'm using visual Studio 2010 and OpenCV 2.4.3 installed on windows7 (32 bit).
Please note that I'm new to OpenCV and just switched from MATLAB. Therefore if you are willing to help, I would be grateful if you could explain clearly.
In MATLAB I could simply right-click on the function and see the source file (for the open source functions only).
Thanks
Payam
DFT function can be found in the dxt.cpp source file. This is located in $opencv2.3$\opencv\modules\core\src
If you save it as the same function you will Overwrite that function and wont be able to use the original function. If you only want your new function then just change the code, if you want the original functionality save it as something else, dft2 would surfice but i suggest saving it as something more meaningfull like dft"whathaveIdone"
Either create some new files etc or just save it as a new function with dxt.cpp, you will need to create function definitions etc
In order to find this information I opened the OpenCV solution in Visual Studio and did a solution wide search for DFT
I use cvBlobsLib for blob detection. At the moment I need large and small eigenvalue and corresponding eingenvectors. All what I could find in the documentation of library is CBlobGetMajorAxisLength and CBlobGetMinorAxisLength. If I am right: first gives me the large eigenvalue and the second - the small eigenvalue. But now I also need eigenvectors which I could not find in the library.
Thank you
It looks like there is a way to get the orientation angle of the blob. Rooting through the documentation (downloaded here, which is not in English, but can be understood) I found:
CBlobGetOrientation Class Reference
Public Member Functions
double operator() (const CBlob &blob) const
Aplica l'operació al blob.
const char * GetNom () const
Obté el nom de l'operador.
So, if you have the magnitude of the axis and it's orientation, you should be able to derive everything else. The only trick is, I'm not sure what the angle is referenced to.