Accessing 3-tuple values of a char*

Question

I am having what is follow:

char* imgData;
Scalar scal = cvGet2D(imgData, x, y);

Where Scalar is defined as below:

typedef struct Scalar
{
double val[3];
}
Scalar;

What I want to have a scalar as a result, but without the use of cvGet2D.

How can I implement that?

@JoachimPileborg, indeed, how to do so? Even in the declaration of cvGet2D, it's not mentioned! — MelMed, Oct 01 '13 at 08:58
please avoid the c-api, as it won't be supported in the near future. — berak, Oct 01 '13 at 08:58
OpenCV is open source. Download the source and look for it there. The problem is that it's most likely going to be much more work for you, and it will be easier to just call a single function which does all the work for you, especially if you are using OpenCV in other parts of the program. — Some programmer dude, Oct 01 '13 at 09:00

score 0 · Accepted Answer · answered Oct 15 '13 at 08:30

0

cvGet2D() must take into account all possible image depths, channel count, etc.
If you know your image format at compile time, you can access the pixels directly via pointer arithmetic.

answered Oct 15 '13 at 08:30

Adi Shavit

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score 0 · Answer 2 · edited May 23 '17 at 12:21

0

Maybe this post will help further:

How do I access a pixel in OpenCV?

In your case is img->imageData simply imgData. To access all your pixels in x and y you still need to know the widthstep (row step) of your image. I would say you have something like:

int x=44;
int y=21;
int widthstep=480;
Scalar pixel = ((Scalar*)imgData)[y*widthstep+x];

edited May 23 '17 at 12:21

Community

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answered Oct 15 '13 at 11:35

jamk

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Accessing 3-tuple values of a char*

2 Answers2