diff --git a/report/pic.go b/report/pic.go
index 3d709db..582a9f1 100644
--- a/report/pic.go
+++ b/report/pic.go
@@ -23,16 +23,34 @@ type Pic struct {
 	Bench    string // optionally set.
 }
 
+type PlotPics []Pic
+
 // PicList is a structure holding a slice of pics and {bench,algo} metadata.
 type PicList struct {
 	Algo  string
 	Bench string
-	Pics  []Pic
+	Pics  PlotPics
 }
 
 //go:embed pics.tmpl
 var tmplPicsFile []byte
 
+// Len implements the sort.Interface.
+func (p PlotPics) Len() int {
+	return len(p)
+}
+
+// Less implements the sort.Interface.
+// note: sorting based on filename
+func (p PlotPics) Less(i, j int) bool {
+	return p[i].FilePath < p[j].FilePath
+}
+
+// Swap implements the sort.Interface.
+func (p PlotPics) Swap(i, j int) {
+	p[i], p[j] = p[j], p[i]
+}
+
 // NewPic returns a new copy of Pic.
 func NewPic() *Pic {
 	return &Pic{}