@ottap
Through our research, we found that data truncation is caused by automatic row height setting. So you need to call method Worksheet.AutoFitRows(true) to automatically adjust the row height. Please refer to the following API.
Please change the following code:
var sheetRender = new SheetRender(worksheet, imageOptions);
To:
worksheet.AutoFitRows(true);
var sheetRender = new SheetRender(worksheet, imageOptions);