chart_exporter.gs

function myFunction() {
  const sheet = SpreadsheetApp.openById(<sheet id>);
  const target_folder = DriveApp.getFolderById(<folder id>);
  const folders = target_folder.getFolders();
  while (folders.hasNext()) {
    const f = folders.next();
    f.setTrashed(true);
  }
  const slides = SlidesApp.create("temp");
  for(const page of sheet.getSheets()){
    var i = 0;
    const charts = page.getCharts();
    if(charts.length > 0){
      const subfolder = target_folder.createFolder(page.getName());
      for(const chart of charts){
          const imageBlob = slides
            .getSlides()[0]
            .insertSheetsChartAsImage(chart)
            .getAs("image/png");
          subfolder.createFile(imageBlob.setName(`${(i+'').padStart(3,'0')}.png`));
          i += 1;
      }
    }
  }
  DriveApp.getFileById(slides.getId()).setTrashed(true);
}