Trouble with OpenCV. Load a image

Asked By thomas ward 250 points N/A Posted on - 05/13/2011

Hi.

I am a student of CSE. I am doing some project using open CV. I need to load a image and save each of the regions predefined in the program, as a separate image. How do i do it in C++?

For example, suppose I have a form with 8 fields, I shall give the pixels from where to crop and the lengths along with it.

The program should crop the image according to the location.

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Answered By softwaresynthesis 0 points N/A #92771

Trouble with OpenCV. Load a image

The concept you are talking about is called Region Of Interest. In short- "ROI". The function for setting region of interest in opencv is

cvSetImageROI();

It takes 2 arguments, first one is the image ( our subject) second one is a rectangle defining the area to be set for ROI.

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Answered By technical007 0 points N/A #92773

Trouble with OpenCV. Load a image

OpenCV is a very powerful tool. If you want to do small works you can use CImg.

Link

It is simple and lightweight.

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Answered By thomas ward 250 points N/A #92775

Trouble with OpenCV. Load a image

@Synthesis,

Thanks. But when I type this:

cvSetImageROI(img, 645,1468,565,75);

it says too many arguments.

@Technical

Thanks to you too. But I am afraid I have to do this in OpenCV.

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Answered By softwaresynthesis 0 points N/A #92777

Trouble with OpenCV. Load a image

Thomas,

By rectangle I literally meant a rectangle. Like this one: cvRect(645,1468,565,75)

So you should use : cvSetImageROI(img, cvRect(645,1468,565,75));

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Answered By thomas ward 250 points N/A #92778

Trouble with OpenCV. Load a image

Thanks again synthesis. It was my misinterpretation. But now I have another problem:

cvSetImageROI(img, cvRect(390,290,280,60));
cvSaveImage("part1.bmp",img);

This works fine but when I add another one;

cvSetImageROI(img, cvRect(390,290,280,60));
cvSaveImage("part1.bmp",img);
cvSetImageROI(img, cvRect(1050,924,679,64));
cvSaveImage("part2.bmp",img);

This crashes just after I run it, giving some horrible printings in the screen. Stating cvImg out of bound.  But my whole image is 3072×1024.

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Answered By softwaresynthesis 0 points N/A #92780

Trouble with OpenCV. Load a image

After the first call of setImageROI.

cvSetImageROI(img, cvRect(390,290,280,60));

Your image becomes 280×60. So next when you say

cvSetImageROI(img, cvRect(1050,924,679,64));

It can’t find the 1050 pixel within 280×60

You have to reset the ROI after each call

cvSetImageROI(img, cvRect(390,290,280,60));
cvSaveImage("part1.bmp",img);
cvResetImageROI(img);

cvSetImageROI(img, cvRect(1050,924,679,64));
cvSaveImage("part2.bmp",img);
cvResetImageROI(img);

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Answered By thomas ward 250 points N/A #92781

Trouble with OpenCV. Load a image

You are most welcome Thank you from my heart!

That was a great support.

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Answered By softwaresynthesis 0 points N/A #92783

Trouble with OpenCV. Load a image

You are most welcome

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• Posted on - 05/14/2011
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