collapse data and transform packages into proxy

proxy/transform.go

@@ -0,0 +1,106 @@
+// Copyright 2013 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package transform handles image transformation such as resizing.
+package proxy
+
+import (
+	"bytes"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
+	"reflect"
+
+	"github.com/disintegration/imaging"
+)
+
+var emptyOptions = new(Options)
+
+// Transform the provided image.
+func Transform(img []byte, opt *Options) ([]byte, error) {
+	if opt == nil || reflect.DeepEqual(opt, emptyOptions) {
+		// bail if no transformation was requested
+		return img, nil
+	}
+
+	// decode image
+	m, format, err := image.Decode(bytes.NewReader(img))
+	if err != nil {
+		return nil, err
+	}
+
+	// convert percentage width and height values to absolute values
+	var h, w int
+	if opt.Width > 0 && opt.Width < 1 {
+		w = int(float64(m.Bounds().Max.X-m.Bounds().Min.X) * opt.Width)
+	} else {
+		w = int(opt.Width)
+	}
+	if opt.Height > 0 && opt.Height < 1 {
+		h = int(float64(m.Bounds().Max.Y-m.Bounds().Min.Y) * opt.Height)
+	} else {
+		h = int(opt.Height)
+	}
+
+	// resize
+	if w != 0 || h != 0 {
+		if opt.Fit {
+			m = imaging.Fit(m, w, h, imaging.Lanczos)
+		} else {
+			if w == 0 || h == 0 {
+				m = imaging.Resize(m, w, h, imaging.Lanczos)
+			} else {
+				m = imaging.Thumbnail(m, w, h, imaging.Lanczos)
+			}
+		}
+	}
+
+	// flip
+	if opt.FlipVertical {
+		m = imaging.FlipV(m)
+	}
+	if opt.FlipHorizontal {
+		m = imaging.FlipH(m)
+	}
+
+	// rotate
+	switch opt.Rotate {
+	case 90:
+		m = imaging.Rotate90(m)
+		break
+	case 180:
+		m = imaging.Rotate180(m)
+		break
+	case 270:
+		m = imaging.Rotate270(m)
+		break
+	}
+
+	// encode image
+	buf := new(bytes.Buffer)
+	switch format {
+	case "gif":
+		gif.Encode(buf, m, nil)
+		break
+	case "jpeg":
+		jpeg.Encode(buf, m, nil)
+		break
+	case "png":
+		png.Encode(buf, m)
+		break
+	}
+
+	return buf.Bytes(), nil
+}