add tests for transformImage

transform.go

@@ -27,6 +27,9 @@ import (
 // compression quality of resized jpegs
 const jpegQuality = 95
 
+// resample filter used when resizing images
+var resampleFilter = imaging.Lanczos
+
 // Transform the provided image.  img should contain the raw bytes of an
 // encoded image in one of the supported formats (gif, jpeg, or png).  The
 // bytes of a similarly encoded image is returned.
@@ -91,12 +94,12 @@ func transformImage(m image.Image, opt Options) image.Image {
 	// resize
 	if w != 0 || h != 0 {
 		if opt.Fit {
-			m = imaging.Fit(m, w, h, imaging.Lanczos)
+			m = imaging.Fit(m, w, h, resampleFilter)
 		} else {
 			if w == 0 || h == 0 {
-				m = imaging.Resize(m, w, h, imaging.Lanczos)
+				m = imaging.Resize(m, w, h, resampleFilter)
 			} else {
-				m = imaging.Thumbnail(m, w, h, imaging.Lanczos)
+				m = imaging.Thumbnail(m, w, h, resampleFilter)
 			}
 		}
 	}

transform_test.go

@@ -0,0 +1,138 @@
+package imageproxy
+
+import (
+	"image"
+	"image/color"
+	"image/draw"
+	"reflect"
+	"testing"
+
+	"github.com/disintegration/imaging"
+)
+
+var (
+	red    = color.NRGBA{255, 0, 0, 255}
+	green  = color.NRGBA{0, 255, 0, 255}
+	blue   = color.NRGBA{0, 0, 255, 255}
+	yellow = color.NRGBA{255, 255, 0, 255}
+)
+
+// newImage creates a new NRGBA image with the specified dimensions and pixel
+// color data.  If the length of pixels is 1, the entire image is filled with
+// that color.
+func newImage(w, h int, pixels ...color.NRGBA) image.Image {
+	m := image.NewNRGBA(image.Rect(0, 0, w, h))
+	if len(pixels) == 1 {
+		draw.Draw(m, m.Bounds(), &image.Uniform{pixels[0]}, image.ZP, draw.Src)
+	} else {
+		for i, p := range pixels {
+			m.Set(i%w, i/w, p)
+		}
+	}
+	return m
+}
+
+func TestTransformImage(t *testing.T) {
+	// ref is a 2x2 reference image containing four colors
+	ref := newImage(2, 2, red, green, blue, yellow)
+
+	// use simpler filter while testing that won't skew colors
+	resampleFilter = imaging.Box
+
+	tests := []struct {
+		src  image.Image // source image to transform
+		opt  Options     // options to apply during transform
+		want image.Image // expected transformed image
+	}{
+		// no transformation
+		{ref, emptyOptions, ref},
+
+		// rotations
+		{ref, Options{Rotate: 45}, ref}, // invalid rotation is a noop
+		{ref, Options{Rotate: 90}, newImage(2, 2, green, yellow, red, blue)},
+		{ref, Options{Rotate: 180}, newImage(2, 2, yellow, blue, green, red)},
+		{ref, Options{Rotate: 270}, newImage(2, 2, blue, red, yellow, green)},
+
+		// flips
+		{
+			ref,
+			Options{FlipHorizontal: true},
+			newImage(2, 2, green, red, yellow, blue),
+		},
+		{
+			ref,
+			Options{FlipVertical: true},
+			newImage(2, 2, blue, yellow, red, green),
+		},
+		{
+			ref,
+			Options{FlipHorizontal: true, FlipVertical: true},
+			newImage(2, 2, yellow, blue, green, red),
+		},
+
+		// resizing
+		{ // can't resize larger than original image
+			ref,
+			Options{Width: 100, Height: 100},
+			ref,
+		},
+		{ // invalid values
+			ref,
+			Options{Width: -1, Height: -1},
+			ref,
+		},
+		{ // absolute values
+			newImage(100, 100, red),
+			Options{Width: 1, Height: 1},
+			newImage(1, 1, red),
+		},
+		{ // percentage values
+			newImage(100, 100, red),
+			Options{Width: 0.50, Height: 0.25},
+			newImage(50, 25, red),
+		},
+		{ // only width specified, proportional height
+			newImage(100, 50, red),
+			Options{Width: 50},
+			newImage(50, 25, red),
+		},
+		{ // only height specified, proportional width
+			newImage(100, 50, red),
+			Options{Height: 25},
+			newImage(50, 25, red),
+		},
+		{ // resize in one dimenstion, with cropping
+			newImage(4, 2, red, red, blue, blue, red, red, blue, blue),
+			Options{Width: 4, Height: 1},
+			newImage(4, 1, red, red, blue, blue),
+		},
+		{ // resize in two dimensions, with cropping
+			newImage(4, 2, red, red, blue, blue, red, red, blue, blue),
+			Options{Width: 2, Height: 2},
+			newImage(2, 2, red, blue, red, blue),
+		},
+		{ // resize in two dimensions, fit option prevents cropping
+			newImage(4, 2, red, red, blue, blue, red, red, blue, blue),
+			Options{Width: 2, Height: 2, Fit: true},
+			newImage(2, 1, red, blue),
+		},
+		{ // scale image explicitly
+			newImage(4, 2, red, red, blue, blue, red, red, blue, blue),
+			Options{Width: 2, Height: 1},
+			newImage(2, 1, red, blue),
+		},
+
+		// combinations of options
+		{
+			newImage(4, 2, red, red, blue, blue, red, red, blue, blue),
+			Options{Width: 2, Height: 1, Fit: true, FlipHorizontal: true, Rotate: 90},
+			newImage(1, 2, red, blue),
+		},
+	}
+
+	for _, tt := range tests {
+		if got := transformImage(tt.src, tt.opt); !reflect.DeepEqual(got, tt.want) {
+			t.Errorf("trasformImage(%v, %v) returned image %#v, want %#v", tt.src, tt.opt, got, tt.want)
+		}
+	}
+}