How to export charts which are dynamically generated by using jquery flot into Excel using C# in asp.net?

Question

I have a aspx page which generates charts using jQuery flot tool. Its working good. My new requirement is I have to place a button called "Export to Excel" in this page. Whenever I click this button, the charts which are generated by jQuery flot tool has to export to excel file as images. Its like copy and paste the image from html page to excel file. I tried so many ways but I cant get proper solution. Help me to solve this.

method 1: 1.In JavaScript, I convert the chart div into canvas and set source of asp image control into that image . Its displaying in browser as expected.

var data = canvas.toDataURL('image/jpg'); 
document.getElementById('ctl00_ctl00_ContentPlaceHolder1_ContentPlaceHolder1_imgChart').src=data;         
}
});

2.But at server I cant access that image src even though I put the submit button in update panel.

string picName = imgChart.ImageUrl;
worksheet.Shapes.AddPicture(picName, Microsoft.Office.Core.MsoTriState.msoFalse, Microsoft.Office.Core.MsoTriState.msoCTrue, 10, 10, 100, 100);

It shows picName is null error.

method 2:

1. Convert the chart into image and store in a local folder
2. Add the image file from folder in the excel

But the problem is cant convert the chart into image and store in local folder.

Answer 1

This behaviour is expected in ASP.NET. Changing the src path (eg the ImageUrl property) with JavaScript of an Image won't be available in the postback.

I would try to store the value of the canvas also in a HiddenField and take the value from there in my server side code.

JavaScript

var data = canvas.toDataURL('image/jpg'); 
document.getElementById('ctl00_ctl00_ContentPlaceHolder1_ContentPlaceHolder1_imgChart').src=data;
document.getElementById('ctl00_ctl00_ContentPlaceHolder1_ContentPlaceHolder1_HiddenField1').value=data;

C#

string picName = HiddenField1.Value;
worksheet.Shapes.AddPicture(picName, Microsoft.Office.Core.MsoTriState.msoFalse, Microsoft.Office.Core.MsoTriState.msoCTrue, 10, 10, 100, 100);

Update : This approach will give you data: URL that will look like this data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADIA .

In order to save this string as an image in C# you need the following code which I found here . After saving this image to the file system (the file "~/temp/file.png" ) you can easily add it to excel.

C#

string data = @"data:image/png;base64,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";

         var base64Data = Regex.Match(data, @"data:image/(?<type>.+?),(?<data>.+)").Groups["data"].Value;
         var binData = Convert.FromBase64String(base64Data);

         using (var stream = new MemoryStream(binData))
         {
             System.Drawing.Image image = new Bitmap(stream);

             image.Save(Server.MapPath("~/temp/file.png"));
         }