Split out encode code from decode, same for tests

images/encode.go

@@ -0,0 +1,38 @@
+package images
+
+import (
+	"image"
+	"image/jpeg"
+	"io"
+	"os"
+)
+
+func RenderAndMakeFile(img image.Image, imgDetail *Details) error {
+	out, err := os.Create(imgDetail.FileName)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	err = Render(out, img, imgDetail)
+	if err != nil {
+		return err
+	}
+
+	fi, _ := out.Stat()
+	imgDetail.SizeFile = fi.Size()
+
+	return nil
+}
+
+func Render(w io.Writer, img image.Image, imgDetail *Details) error {
+	// Currently a wrapper for renderJpeg, but this function is useful if multiple render formats are needed
+	return renderJpeg(w, img, imgDetail)
+}
+
+func renderJpeg(w io.Writer, m image.Image, imgDetail *Details) error {
+	o := new(jpeg.Options)
+	o.Quality = imgDetail.Quality
+
+	return jpeg.Encode(w, m, o)
+}

images/encode_test.go

@@ -0,0 +1,94 @@
+package images
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRender(t *testing.T) {
+	cs := []struct {
+		FileName   string
+		RenderSize int
+	}{
+		{
+			"elephant.jpg",
+			1447,
+		},
+		{
+			"rose.webp",
+			11119,
+		},
+		{
+			"spin.gif",
+			2263,
+		},
+		{
+			"status.png",
+			5834,
+		},
+	}
+	options := Details{
+		Quality: 70,
+	}
+
+	for _, c := range cs {
+		img, err := Get(path + c.FileName)
+		require.NoError(t, err)
+
+		bb := bytes.NewBuffer([]byte{})
+		err = Render(bb, img, &options)
+		require.NoError(t, err)
+
+		require.Exactly(t, c.RenderSize, bb.Len())
+	}
+}
+
+func TestMakeAndRenderFile(t *testing.T) {
+	cs := []struct {
+		FileName   string
+		OutName    string
+		OutputSize int64
+	}{
+		{
+			"elephant.jpg",
+			"_elephant.jpg",
+			1447,
+		},
+		{
+			"rose.webp",
+			"_rose.jpg",
+			11119,
+		},
+		{
+			"spin.gif",
+			"_spin.jpg",
+			2263,
+		},
+		{
+			"status.png",
+			"_status.jpg",
+			5834,
+		},
+	}
+
+	for _, c := range cs {
+		img, err := Get(path + c.FileName)
+		require.NoError(t, err)
+
+		options := &Details{
+			FileName: path + c.OutName,
+			Quality:  70,
+		}
+
+		err = RenderAndMakeFile(img, options)
+		require.NoError(t, err)
+		require.Exactly(t, c.OutputSize, options.SizeFile)
+
+		// tidy up
+		err = os.Remove(options.FileName)
+		require.NoError(t, err)
+	}
+}