Webcam supported picture sizes

Question

I am attempting to retrieve the available picture-size resolutions supported by my webcam; using the OpenCV library. I have tried working with similar Android question/answers but to no avail. (e.g. Android camera supported picture sizes). Here is my code:

import org.opencv.highgui.VideoCapture;
import org.opencv.core.Size;

public class MyCameraCaptureClass {

public static void main(String[] args) {
    System.out.println("Hello, OpenCV");
    System.out.println("This program will display the webcam's supported sizes");

    System.loadLibrary("opencv_java248"); //load .dll for the jar

    VideoCapture vidCap0 = new VideoCapture(0);

    if (vidCap0.isOpened()) {
        System.out.println("Camera found, and it works so far...");

        for (Size aSize : vidCap0.getSupportedPreviewSizes()) {
            System.out.println("Doesn't print this at all");
            System.out.println("Height:" + aSize.height + "Width:" + aSize.width);
        }
    }
    vidCap0.release();
    }
}

And the stack trace is:

Exception in thread "main" java.lang.Exception: unknown exception
at org.opencv.highgui.VideoCapture.getSupportedPreviewSizes_0(Native Method)
at org.opencv.highgui.VideoCapture.getSupportedPreviewSizes(VideoCapture.java:478)
at webcam.MyCameraCaptureClass.main(MyCameraCaptureClass.java:19)

All help will be sincerely appreciated.

Answer 1

As noted in the comments this is a reported bug that has been listed as corrected for 2.4.9:

• http://code.opencv.org/issues/3387
• http://code.opencv.org/issues/3477

That said, the project is open source, and looking at the code change that corrects this, it is a simple fix. You could just implement that bug fix and build it yourself to use until 2.4.9 is released. The associated revision is here:

• In the VideoCapture.cpp file: REVISION 5f88e2b4

Lines 332->335:

Replace:

return env->NewStringUTF(u.name);

With:

// VideoCapture::get can return 0.0 or -1.0 if it doesn't support
// CV_CAP_PROP_SUPPORTED_PREVIEW_SIZES_STRING
if (u.prop != 0.0 && u.prop != -1.0)
    return env->NewStringUTF(u.name);