rauwendaal.net - OpenCV (and OpenGL)

So I started using OpenCV for my Computer Vision class, but I didn’t want to give up my OpenGL based framework, and since I had such a hard time finding any hints on how to convert OpenCV Images to OpenGL textures, I’m going to post the technique I used here. What I did eventually find was this, which didn’t immediately work for me as written.

So OpenCV images are stored in these IplImage structs, and they’re actually pretty great because they load just about anything

IplImage *image = cvLoadImage("filename");

So after you create you OpenCV Image, how do you get an OpenGL texture. Well, OpenCV images are stored as unsigned bytes so so you’re going to want your texturetype to be GL_UNSIGNED_BYTE, and most of the other parameters to pass to glTexImage2D come right out of the IplImage struct, the only thing to be wary of is swapping the RGB colors, if you don’t, red will look blue, and blue will look red. So be sure to set internalFormat to GL_RGB, and format to GL_BGR like so

glTexImage2D(GL_TEXTURE_2D,        //target
             0,                    //level
             GL_RGB,               //internalFormat
             image->width,         //width
             image->height,        //height
             0,                    //border
             GL_BGR,               //format
             GL_UNSIGNED_BYTE,     //type
             image->imageData);    //pointer to image data

Of course, this only works if your Image is color, if your Image is grayscale your going to want to change GL_BGR to GL_LUMINANCE

glTexImage2D(GL_TEXTURE_2D,        //target
             0,                    //level
             GL_RGB,               //internalFormat
             image->width,         //width
             image->height,        //height
             0,                    //border
             GL_LUMINANCE,         //format
             GL_UNSIGNED_BYTE,     //type
             image->imageData);    //pointer to image data

And you could probably change the internal format of the OpenGL texture as well, but I don’t presume to know what you want to do with this. And one more snippet for good measure, this time loading a color image and converting it to a gray scale image all in OpenCV.

IplImage *color_image = cvLoadImage("filename");
IplImage *grayscale = cvCreateImage(cvGetSize(color_image), 8, 1);
cvCvtColor(color_image, grayscale, CV_BGR2GRAY);

Citation

BibTeX citation:

@online{rauwendaal2008,
  author = {Randall Rauwendaal},
  title = {OpenCV (and {OpenGL)}},
  date = {2008-10-27},
  url = {https://raegnar.github.io/rauwendaal.net//posts/2008_10_27 - OpenCV (and OpenGL)},
  langid = {en}
}

For attribution, please cite this work as:

Randall Rauwendaal. 2008. “OpenCV (and OpenGL).” October 27, 2008. https://raegnar.github.io/rauwendaal.net//posts/2008_10_27 - OpenCV (and OpenGL).