Refactor

domain/resize/resize.go

@@ -0,0 +1,105 @@
+package resize
+
+import (
+	"bytes"
+	"github.com/anthonynsimon/bild/transform"
+	"image"
+	"image/jpeg"
+	"image/png"
+	"io"
+)
+
+var mimeTypes = map[string]string{
+	"image/jpg":  "image/jpg",
+	"image/jpeg": "image/jpeg",
+	"image/png":  "image/png",
+}
+
+func IsResizable(mimeType string) bool {
+	_, present := mimeTypes[mimeType]
+	return present
+}
+
+type ResizeType int
+
+const (
+	// Cover - resize preserving image aspect
+	//       - resizes to the smallest image where both width and height are larger or equal to given size
+	Cover ResizeType = iota
+	// Contain - resize preserving image aspect
+	//       - resizes to the largest image where both width and height are smaller or equal to given size
+	Contain ResizeType = iota
+	// ExactHeight - resize preserving image aspect
+	//       - resizes to the image with given height
+	ExactHeight ResizeType = iota
+	// ExactWidth - resize preserving image aspect
+	//       - resizes to the image with given width
+	ExactWidth ResizeType = iota
+	// Exact - resize without preserving image aspect
+	//       - resizes to exact size defined in request
+	Exact ResizeType = iota
+)
+
+type Resize struct {
+	Height int
+	Width  int
+	Type   ResizeType
+}
+
+func ResizeImage(imageBytes []byte, resize Resize) ([]byte, error) {
+	img, format, err := image.Decode(bytes.NewReader(imageBytes))
+	if err != nil {
+		return nil, err
+	}
+	var buffer bytes.Buffer
+	writer := io.Writer(&buffer)
+
+	resizeWidth, resizeHeight := calculateResizedDimensions(img.Bounds(), resize)
+
+	img = transform.Resize(img, resizeWidth, resizeHeight, transform.Gaussian)
+	switch format {
+	case "png":
+		err = png.Encode(writer, img)
+	case "jpeg":
+		err = jpeg.Encode(writer, img, nil)
+	default:
+		err = jpeg.Encode(writer, img, nil)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return buffer.Bytes(), nil
+}
+
+func calculateResizedDimensions(bounds image.Rectangle, resize Resize) (width int, height int) {
+	width = bounds.Dx()
+	height = bounds.Dy()
+
+	switch resize.Type {
+	case Cover:
+		rWidth := resize.Height * width / height
+		if rWidth >= resize.Width {
+			return rWidth, resize.Height
+		}
+		rHeight := resize.Width * height / width
+		if rHeight >= resize.Height {
+			return resize.Width, rHeight
+		}
+	case Contain:
+		rWidth := resize.Height * width / height
+		if rWidth <= resize.Width {
+			return rWidth, resize.Height
+		}
+		rHeight := resize.Width * height / width
+		if rHeight <= resize.Height {
+			return resize.Width, rHeight
+		}
+	case ExactHeight:
+		rWidth := resize.Height * width / height
+		return rWidth, resize.Height
+	case ExactWidth:
+		rHeight := resize.Width * height / width
+		return resize.Width, rHeight
+	}
+	return
+}