and I wrote following codes to get the photo's data by two ways

1.
            set imagedatafile [open "C:/imagedata.txt" "w+"]
            fconfigure $imagedatafile -translation binary
            puts $imagedatafile [$theIm data -format jpeg]
            close $imagedatafile

2.
            set fileName "C:/Winter.jpg"
            set fd [open $fileName r]
            fconfigure $fd -translation binary
            set imagebase64file [open "C:/imagebase64.txt" "w+"]
            fconfigure $imagebase64file -translation
binary
            puts $imagebase64file [::base64::encode [read $fd]]
            close $fd
            close $imagebase64file

But I found the C:/imagedata.txt is very different from the C:/
imagebase64.txt

anyone knows why this happen?