refactor(watermark): auto define width

image_test.go

@@ -168,7 +168,7 @@ func TestImageWatermarkNoReplicate(t *testing.T) {
 func TestImageZoom(t *testing.T) {
 	image := initImage("test.jpg")
 
-	_, err := image.Extract(100, 100, 0, 0)
+	_, err := image.Extract(100, 100, 400, 300)
 	if err != nil {
 		t.Errorf("Cannot extract the image: %s", err)
 	}
@@ -180,7 +180,7 @@ func TestImageZoom(t *testing.T) {
 
 	err = assertSize(buf, 800, 600)
 	if err != nil {
-		//t.Error(err)
+		t.Error(err)
 	}
 
 	Write("fixtures/test_zoom_out.jpg", buf)

resize.go

@@ -208,7 +208,7 @@ func watermakImage(image *C.struct__VipsImage, w Watermark) (*C.struct__VipsImag
 		w.Font = "sans 10"
 	}
 	if w.Width == 0 {
-		w.Width = int(math.Floor(float64(image.Xsize / 8)))
+		w.Width = int(math.Floor(float64(image.Xsize / 6)))
 	}
 	if w.DPI == 0 {
 		w.DPI = 150