Thanks for your posting and using Aspose.Cells for .NET.
We have looked into your issue and tested it with the latest version: Aspose.Cells
for .NET v188.8.131.52 and found it is actually a bug.
We have logged this issue in our database. We will look into this issue and fix it. Once the issue is fixed or we have some other update for you, we will let you know asap.
This issue has been logged as CELLSNET-41252.
Please see the following test code. I have attached the output image generated by it for a reference.
string filePath = @“F:\Shak-Data-RW\Downloads\chart.xlsx”;
Workbook workbook = new Workbook(filePath);
Worksheet worksheet = workbook.Worksheets;
Chart chart = worksheet.Charts;
Bitmap bmp = chart.ToImage();
bmp.Save(filePath + “.out.png”, ImageFormat.Png);