Install-Package FreeSpire.XLS

using Spire.Xls;
using System.Drawing;

Workbook workbook = new Workbook();
workbook.LoadFromFile("Sample.xlsx");

// 遍歷所有工作表及其圖表，保存為圖片
foreach (Worksheet sheet in workbook.Worksheets)
{
    foreach (Chart chart in sheet.Charts)
    {
        Bitmap chartImage = chart.SaveToImage();
        chartImage.Save($"output/{sheet.Name} - {chart.ChartTitle}.jpg");
    }
}
workbook.Dispose();

Sub SaveAllChartsAsImages()
    Dim ws As Worksheet
    Dim chartObj As ChartObject
    Dim folderPath As String
    Dim chartIndex As Integer
    Dim fileName As String
    
    ' 設置保存路徑
    folderPath = ThisWorkbook.Path & "\Charts"
    If Dir(folderPath, vbDirectory) = "" Then MkDir folderPath
    
    chartIndex = 1 ' 圖片命名編號
    
    ' 遍歷所有工作表
    For Each ws In ThisWorkbook.Worksheets
        ' 遍歷工作表中的所有圖表對象
        For Each chartObj In ws.ChartObjects
            fileName = folderPath & "\" & ws.Name & "_Chart" & chartIndex & ".jpg"
            chartObj.Chart.Export Filename:=fileName, FilterName:="JPG"
            chartIndex = chartIndex + 1
        Next chartObj
    Next ws
    
    MsgBox "所有圖表已保存為圖片。", vbInformation
End Sub