Add benchmark for adding images to sheet (#367)

* Add benchmark for adding images to sheet

This should help track performance regressions in future changes.

* Only transform sheet name if necessary

1 files changed, 20 insertions, 0 deletions

diff --git a/picture_test.go b/picture_test.go
new file mode 100644
index 0000000..97d3cd9
--- /dev/null
+++ b/picture_test.go
@@ -0,0 +1,20 @@
+package excelize
+
+import (
+	"fmt"
+	_ "image/png"
+	"io/ioutil"
+	"testing"
+)
+
+func BenchmarkAddPictureFromBytes(b *testing.B) {
+	f := NewFile()
+	imgFile, err := ioutil.ReadFile("logo.png")
+	if err != nil {
+		panic("unable to load image for benchmark")
+	}
+	b.ResetTimer()
+	for i := 1; i <= b.N; i++ {
+		f.AddPictureFromBytes("Sheet1", fmt.Sprint("A", i), "", "logo", ".png", imgFile)
+	}
+}