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2015-03-10 17:02:53 -0500 commented answer Is there a way to easily plot pixels?

Thanks berak. This might be a dumb question, but why is it (y, x) instead of (x, y)? Is that just the convention when you do <Vec3b>? Or is it because you are using

EDIT: Nevermind, I looked at the documentation.

2015-03-10 16:54:39 -0500 commented answer Is there a way to easily plot pixels?

Thanks for the help. Since I want multiple circles, I have to apply the circle function multiple times? Also, doesn't this exceed the size of one pixel? What I mean by this is let's say the circle radius is one, this will technically circle around more than one pixel because the pixel value is just the center, correct?

Other question, let's say I use<uchar>(Point(x, y)) = 0; does uchar work for CV_8U datatype? Sorry, I know that question is really basic. And finally, let's say I want to make the color turquoise instead of black. Do I say:<uchar>(Point(x, y)) = Scalar(R,G,B); where R,G,B are the proper values for whatever color I want?

2015-03-10 16:19:30 -0500 asked a question Is there a way to easily plot pixels?

Let's say I have a Mat M which contains a grayscale image. Now I apply a colormap to make a new Mat M_color and show the image. The colormap is fine, but at specific points (where I already know the indices), I want to make the pixels a specific color (let's say black).

Example: I have a 25x25 grayscale image shown with a rainbow colormap. At pixels (2,7), (4,12), (16,9), and (14,23) I want them to be black.

Is there an easy way to plot the black pixels over-top the rainbow image? Or if it's easier, to just change the color at that specific instance to black.

2015-02-23 12:02:11 -0500 asked a question applyColormap for CV_64F matrix?

I've been trying to use the applyColormap function. I'm working with a matrix with a datatype of CV_64F. If I apply a color map, the image is still B&W (using imshow). But if I convert the matrix to CV_8U, then apply the color map, it works. This is fine for right now, but later on I will need to apply a color map to a matrix with datatype CV_64F and I will not be able to convert it to CV_8U because it will have negative values and decimal points.

Any suggestions would be greatly appreciated.

2015-02-20 11:35:31 -0500 commented answer Sine or Cosine of every element in Mat (c++)

^^Sorry, I didn't know -.- I will make sure to keep it open!

2015-02-19 19:02:01 -0500 commented question How to detect labels with numbers in a black rectangle?

That sounds like cool project! I think you will definitely need closer images than that/possibly take them when you are parallel to the surface so there isn't much perspective. I would guess 2 or 3 feet away would be fine. Once you have the code working on something like that, you can start to optimize it for images that aren't so perfect.

Like thdrksdfthmn said, you should start by setting a threshold so it is high contrast B&W. However, I think that before you do the thresholding to high-contrast black & white, you should invert the image colors. This might make it easier on the Cascade classifiers. Let me know if that helps, and if it doesn't I can think a little bit harder :p. Good luck!!

2015-02-19 16:50:59 -0500 commented question How to detect labels with numbers in a black rectangle?

I'm new to OpenCV as well, but I might be able to help. When you take the images from the camera, are they going to be focused on the labels? Or will they be similar to the image you have posted, where the image is distant and you are far away from the labels?

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2015-02-19 09:58:50 -0500 commented answer Sine or Cosine of every element in Mat (c++)

That's exactly what I ended up doing! Thanks (: +1

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2015-02-18 09:55:57 -0500 asked a question Sine or Cosine of every element in Mat (c++)

I was wondering if there is any way to take the sine or cosine of every element in a matrix?


EDIT: For future reference, I did the Taylor expansion of Sine. For pretty good accuracy, I only had to calculate up to the fourth term. However, keep note that if you are trying to estimate sin(pi) or sin(-pi) you have to calculate additional terms (probably 8 total terms).

This link will be useful for those who want to do this: