// Load a GIF and save each of its pages as a BMP File
ImageEnView1.IO.LoadFromFile('C:\input.gif');  // Load first image to get valid value for Params.ImageCount
for I := 0 to ImageEnView1.IO.Params.ImageCount - 1 do
begin
  ImageEnView1.IO.Params.ImageIndex := I;
  ImageEnView1.IO.LoadFromFile('C:\input.gif');
  ... Check for barcodes ...
end;

OR

idx := 0;
ImageEnView1.IO.LoadFromFile('C:\input.tif');
 ... Check for barcodes ...
while ImageEnView1.IO.Seek( ieioSeekNext ) <> idx do
begin
  ImageEnView1.IO.PrintImage();
  ... Check for barcodes ...
  inc(idx);
end