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javaopencvimage-processingopencv3.0javacv

Trying to change color of a small png image using OpenCV (Java)

Here I am using OpenCV lib with java to change the transparent part as White and the shapes inside on it to black color and little thick. I tried to use cvtColor(img, hsv, Imgproc.COLOR_BGR2GRAY); but the whole image changed to gray. I need help with this

Here is the Original image Which i need to change color

image

System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
String img_url1 = "C:\\\\Users\\\\me\\\\Desktop\\\\cpt\\\\1.png";
Mat img = Imgcodecs.imread(img_url1);
if( img.empty() ) {
    System.out.println("Error opening image!");
    System.out.println("Program Arguments: [image_name -- default ../data/lena.jpg] \n");
    System.exit(-1);
}


Mat hsv = new Mat();
Imgproc.cvtColor(img, hsv, Imgproc.COLOR_BGR2GRAY);

Imgcodecs.imwrite("C:\\\\Users\\\\me\\\\Desktop\\\\cpt\\\\1-cpy.png", hsv);

Outupt image after processing:

image

Solution

  • This is a C++ code but you can easily convert it to JAVA.

      Mat img = imread("image.png",-1);

  //split channels, extract 3rd channel
  std::vector<Mat> channels;
  split(img, channels);

  // convert to white background and black foreground
  Mat black;
  bitwise_not(channels.at(3), black);


  imshow("image", black);
  waitKey(0);

    result