Re: [javacv] Converting image to grayscale using cvCvtColor is giving an error

[Samuel Audet]

On 03/30/2013 01:24 AM, Bhaarat Sharma wrote:
> What am I doing wrong?

`new CvMat()` doesn't allocate memory for the buffer.. This is based on
the old C API. Use cvCreateImage() or the create() factory method as
shown in the README.txt file.

[Alankar dasare]

        String fileName = "nandu.jpg";

        IplImage img=cvLoadImage(fileName);

        CvSize cvSize = cvSize(img.width(), img.height());

        IplImage gry=cvCreateImage(cvSize, img.depth(), 1);

        cvCvtColor(img, gry, CV_BGR2GRAY);

        cvShowImage("gray image",gry);

        cvSaveImage("kumar.jpg", gry);

        cvWaitKey(0);

[Samuel Audet]

So, what is the error that you are getting?

[melo]

Hi Samuel,

I have to convert some part of a C code in Java code, so I use Javacv libraries.However, I don't succed in convert somme parts. For example,

 cvCvtColor( image, grey, CV_BGR2GRAY );

=> cvCvtColor cannot be resolved

image = cvCreateImage( cvGetSize(frame), 8, 3 );   

=>cvGetSize cannot be resolved

I try to change this

frame = cvCreateImage( cvSize(leftImage->width,leftImage->height), leftImage->depth, leftImage->nChannels);

into this

frame = cvCreateImage( cvSize(leftImage.width(),leftImage.height()), leftImage.depth(), leftImage.nChannels());

but cvSize cannot be resolved...

And I don't know if I can convert this

 image->origin = frame->origin; 

in java?

Thank you in advance for your help

Melo

[Samuel Audet]

Hello,

On 05/28/2014 02:03 PM, melo wrote:
> I have to convert some part of a C code in Java code, so I use Javacv
> libraries.However, I don't succed in convert somme parts. For example,
>
> cvCvtColor( image, grey, CV_BGR2GRAY );
> => cvCvtColor cannot be resolved
>
> image = cvCreateImage( cvGetSize(frame), 8, 3 );
> =>cvGetSize cannot be resolved
>
> I try to change this
> frame = cvCreateImage( cvSize(leftImage->width,leftImage->height), leftImage->depth, leftImage->nChannels);
> into this
> frame = cvCreateImage( cvSize(leftImage.width(),leftImage.height()), leftImage.depth(), leftImage.nChannels());
> but cvSize cannot be resolved...

It's all there, just make sure to import static everything from
opencv_core and opencv_imgproc as shown in the README file.

> And I don't know if I can convert this
> image->origin = frame->origin;
> in java?

Sure, that would be
image.origin(frame.origin());

Samuel

[melo]

Hi!

thank you for your answer.

However for this 

frame = cvCreateImage( cvSize(leftImage.width(),leftImage.height()), leftImage.depth(), leftImage.nChannels());

I don't really understand....

In fact I think when i write cvSize , it doesn't like because leftImage is an IplImage from import org.bytedeco.javacpp.opencv_core.IplImage; , I don't know , but I've imported all opencv_core and opencv_imgproc . So i don't know why it doesn't work (I suppose that arguments inside parentheses are wrong)....

My other problem is , Do you know how I convert a * in java, I'm not sure but I think in java a "pointer * " doesn't exist...

Thank you

Melo

[Samuel Audet]

Hi,

On 05/29/2014 08:38 AM, melo wrote:
> However for this

> frame = cvCreateImage( cvSize(leftImage.width(),leftImage.height()), depth(), leftImage.nChannels());

> I don't really understand....
>
> In fact I think when i write cvSize , it doesn't like because leftImage
> is an IplImage from import org.bytedeco.javacpp.opencv_core.IplImage; ,
> I don't know , but I've imported all opencv_core and opencv_imgproc . So
> i don't know why it doesn't work (I suppose that arguments inside
> parentheses are wrong)....

We can do `import static org.bytedeco.javacpp.opencv_core.*` as shown in
the README.md file, and that should do what you want.

Try to run the Demo file from the README.md file, it works right? So do
something similar.

> My other problem is , Do you know how I convert a * in java, I'm not
> sure but I think in java a "pointer * " doesn't exist...

It's mapped to `org.bytedeco.javacpp.Pointer` and we can usually just
remove it. :)

Samuel