diff --git a/transform.go b/transform.go
index bba0176..b37d0ca 100644
--- a/transform.go
+++ b/transform.go
@@ -79,7 +79,9 @@ func Transform(img []byte, opt Options) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
-func resizeParams(m image.Image, opt *Options) (w, h int, resize bool) {
+// resizeParams determines if the image needs to be resized, and if so, the
+// dimensions to resize to.
+func resizeParams(m image.Image, opt Options) (w, h int, resize bool) {
 	// convert percentage width and height values to absolute values
 	imgW := m.Bounds().Max.X - m.Bounds().Min.X
 	imgH := m.Bounds().Max.Y - m.Bounds().Min.Y
@@ -98,7 +100,7 @@ func resizeParams(m image.Image, opt *Options) (w, h int, resize bool) {
 		h = int(opt.Height)
 	}
 
-	// never resize larger than the original image
+	// never resize larger than the original image unless specifically allowed
 	if !opt.ScaleUp {
 		if w > imgW {
 			w = imgW
@@ -107,10 +109,12 @@ func resizeParams(m image.Image, opt *Options) (w, h int, resize bool) {
 			h = imgH
 		}
 	}
+
 	// if requested width and height match the original, skip resizing
 	if (w == imgW || w == 0) && (h == imgH || h == 0) {
 		return 0, 0, false
 	}
+
 	return w, h, true
 }
 
@@ -118,7 +122,7 @@ func resizeParams(m image.Image, opt *Options) (w, h int, resize bool) {
 // in opt.
 func transformImage(m image.Image, opt Options) image.Image {
 	// resize if needed
-	if w, h, resize := resizeParams(m, &opt); resize {
+	if w, h, resize := resizeParams(m, opt); resize {
 		if opt.Fit {
 			m = imaging.Fit(m, w, h, resampleFilter)
 		} else {
diff --git a/transform_test.go b/transform_test.go
index 1a59816..ca3f5f0 100644
--- a/transform_test.go
+++ b/transform_test.go
@@ -40,8 +40,8 @@ func newImage(w, h int, pixels ...color.NRGBA) image.Image {
 func TestResizeParams(t *testing.T) {
 	src := image.NewNRGBA(image.Rect(0, 0, 64, 128))
 	tests := []struct {
-		opt  Options
-		w, h int
+		opt    Options
+		w, h   int
 		resize bool
 	}{
 		{Options{Width: 0.5}, 32, 0, true},
@@ -52,10 +52,10 @@ func TestResizeParams(t *testing.T) {
 		{Options{Width: 64}, 0, 0, false},
 		{Options{Height: 128}, 0, 0, false},
 	}
-	for ti, tt := range tests {
-		w, h, resize := resizeParams(src, &tt.opt)
+	for _, tt := range tests {
+		w, h, resize := resizeParams(src, tt.opt)
 		if w != tt.w || h != tt.h || resize != tt.resize {
-			t.Errorf("test %d problem, want: %d,%d,%t got: %d,%d,%t", ti, tt.w, tt.h, tt.resize, w, h, resize)
+			t.Errorf("resizeParams(%v) returned (%d,%d,%t), want (%d,%d,%t)", tt.opt, w, h, resize, tt.w, tt.h, tt.resize)
 		}
 	}
 }