JavaCV Perspective Transform Gives Error

Question

I am working on an application with Java that corrects the perspective (also called keystoning). To do this, I am using Bytedeco's JavaCV . By referring to documentations and several other websites and manuals online, I tried to do this by using two OpenCV methods, warpPerspective and cvGetPerspectiveTransform . More specifically, this is my code:

public static void main(String[] args) {
    IplImage img = new IplImage(imread("src/res/mona-lisa.jpg"));
    IplImage img2 = new IplImage(3);

    CvMat mmat = cvCreateMat(3, 3, CV_32FC1);
    CvPoint2D32f c1 = new CvPoint2D32f(4);
    CvPoint2D32f c2 = new CvPoint2D32f(4);

    c1.position(0).put(0, 0);
    c1.position(1).put(400, 0);
    c1.position(2).put(0, 300);
    c1.position(3).put(400, 300);

    c2.position(0).put(0, 0);
    c2.position(1).put(img.width(), 0);
    c2.position(2).put(0, img.height());
    c2.position(3).put(img.width(), img.height());

    mmat = cvGetPerspectiveTransform(c1, c2, mmat);
    cvWarpPerspective(img, img2, mmat);

    cvNamedWindow("Image", 1);
    cvShowImage("Image", img);
    cvWaitKey();
}

If I execute that code, the console gives me an "OpenCV Error: Bad argument (Unknown array type) in cv::cvarrToMat, file src\\matrix.cpp, line 880", and, one of these:

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  EXCEPTION_UNCAUGHT_CXX_EXCEPTION (0xe06d7363) at pc=0x00007ffb1e24a1c8, pid=2020, tid=12660
#
# JRE version: Java(TM) SE Runtime Environment (8.0_66-b18) (build 1.8.0_66-b18)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (25.66-b18 mixed mode windows-amd64 compressed oops)
# Problematic frame:
# C  [KERNELBASE.dll+0x2a1c8]
#
# Failed to write core dump. Minidumps are not enabled by default on client versions of Windows
#
# An error report file with more information is saved as:
# ...
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.java.com/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#

However, I know that mona-lisa.jpg is being read properly because if I skip all the mmat process then it renders the original image correctly.

I am trying to achieve something similar to this .

Any thoughts?

Answer 1

Isn't this supposed to store the result in a different image (img2)?

cvWarpPerspective(img, img, mmat);

Also about the crash - it's a long issue that someone suggested it has to do with scoping the variables. Maybe you can check the latest innovations