$ go get github.com/mantyr/swf
package main
import (
"github.com/mantyr/swf"
"fmt"
)
func main() {
s, err := swf.Open("./testdata/f0673319418b054b4f108c18736a042f5dcec4e2123401c48a727dfaab7354ef.swf")
fmt.Println(s.Width()) // 640
fmt.Println(s.Height()) // 480
}