How to pass image from bootstrap modal popup to parent page?

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C#

Javascript

hello,
i want to pass captured image by webcam from modal popup page to parent page on image control. everything is working fine but when i pass image, image is appearing on image control but while save time its value showing null.

i try to method
1) in this method i have call captuteimage.aspx page as a popup page in this method image is passing from captureimage.aspx page to parent page. but image value showing me null while saving

2) in this method i have use bootstrap modal popup to capture image crop and upload process. in this method image capturing but when i press crop button the modal popup close automatically and not allow me to do rest process like crop and upload.
i have use same code in modal to pass image from modal popup to parent page but on crop button click its close itself...

i have search many articles but still not done please help me to resolve this..
thanks in advance...

What I have tried:

child page captureimage.aspx pass image code

function passDetails() {
    if (window.opener != null && !window.opener.closed) {
        //alert('begin');
        var vImage = window.opener.document.getElementById("vImage");
        window.opener.SetSource(document.getElementById("imgCapture").src);
                }
    window.close();
}

parent page code for access image.

<script>
        function myFunction() {
            var url = "/captureimage.aspx";
            var s = window.open(url, 'popup_window', 'width=900,height=500,left=200,top=100,resizable=no');
            ClientScript.RegisterStartupScript(this.GetType(), "script", s, true);
        }
        function SetSource(src) {
            document.getElementById("vImage").src = src;
            //document.getElementById("vimagehidden").value = src;
        }
    </script>

this is my modal popup code...

<div class="modal fade" id="exampleModal" data-index="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true" data-keyword="false" data-backdrop="static">
                        <div class="modal-dialog modal-lg" role="document">
                            <div class="modal-content">
                                <div class="modal-header text-center">
                                    <div class="mx-auto">
                                        <h6 class="modal-title text-center" id="exampleModalLabel">Capture Image</h6>
                                    </div>
                                    <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                                        <span aria-hidden="true">&times;</span>
                                    </button>
                                </div>
                                <div class="modal-body">
                                    <div class="card">
                                        <div class="card-body">
                                            <div class="row">
                                                <div class="col-md-6">
                                                    <div class="form-group">
                                                        <div id="webcam" style="height: 240px; width: 320px;"></div>
                                                    </div>
                                                    <div class="form-group text-center">
                                                        <%--<asp:Button ID="btnCapture" runat="server" Text="Capture" CssClass="btn btn-success" />--%>
                                                        <input type="button" id="btnCapture" value="Capture" class="btn btn-success" />
                                                    </div>
                                                </div>

                                                <div class="col-md-6">
                                                    <div class="form-group">
                                                        <asp:Image ID="imgCapture" runat="server" Height="240" Width="320" />
                                                            <asp:HiddenField ID="X" runat="server" />
                                                            <asp:HiddenField ID="Y" runat="server" />
                                                            <asp:HiddenField ID="W" runat="server" />
                                                            <asp:HiddenField ID="H" runat="server" />
                                                    </div>
                                                    
                                                </div>
                                            </div>
                                        </div>
                                    </div>
                                </div>
                                <div class="modal-footer">
                                <div class="form-group text-center">
                                    <%--<input type="button" id="btnCrop" value="Crop" class="btn btn-success" />--%>
                                    <asp:Button ID="btnCrop" runat="server" Text="Crop" CssClass="btn btn-success" OnClick="btnCrop_Click" />
                                    &nbsp;&nbsp;
                                    <asp:Button ID="btnUpload" runat="server" Text="Upload" CssClass="btn btn-success" OnClientClick="passDetails();" />
                                </div>
                            </div>
                            </div>
                            
                        </div>
                    </div>