[#87] added additional thumb resizers

tools/filesystem/filesystem.go

@@ -3,10 +3,12 @@ package filesystem
 import (
 	"context"
 	"errors"
+	"image"
 	"io"
 	"net/http"
 	"os"
 	"path/filepath"
+	"regexp"
 	"sort"
 	"strconv"
 	"strings"
@@ -230,18 +232,31 @@ func (s *System) Serve(response http.ResponseWriter, fileKey string, name string
 	return err
 }
 
+var ThumbSizeRegex = regexp.MustCompile(`^(\d+)x(\d+)(t|b|f)?$`)
+
 // CreateThumb creates a new thumb image for the file at originalKey location.
 // The new thumb file is stored at thumbKey location.
 //
-// thumbSize is in the format "WxH", eg. "100x50".
-func (s *System) CreateThumb(originalKey string, thumbKey, thumbSize string, cropCenter bool) error {
-	thumbSizeParts := strings.SplitN(thumbSize, "x", 2)
-	if len(thumbSizeParts) != 2 {
-		return errors.New("Thumb size must be in WxH format.")
+// thumbSize is in the format:
+// - 0xH  (eg. 0x100)    - resize to H height preserving the aspect ratio
+// - Wx0  (eg. 300x0)    - resize to W width preserving the aspect ratio
+// - WxH  (eg. 300x100)  - resize and crop to WxH viewbox (from center)
+// - WxHt (eg. 300x100t) - resize and crop to WxH viewbox (from top)
+// - WxHb (eg. 300x100b) - resize and crop to WxH viewbox (from bottom)
+// - WxHf (eg. 300x100f) - fit inside a WxH viewbox (without cropping)
+func (s *System) CreateThumb(originalKey string, thumbKey, thumbSize string) error {
+	sizeParts := ThumbSizeRegex.FindStringSubmatch(thumbSize)
+	if len(sizeParts) != 4 {
+		return errors.New("Thumb size must be in WxH, WxHt, WxHb or WxHf format.")
 	}
 
-	width, _ := strconv.Atoi(thumbSizeParts[0])
-	height, _ := strconv.Atoi(thumbSizeParts[1])
+	width, _ := strconv.Atoi(sizeParts[1])
+	height, _ := strconv.Atoi(sizeParts[2])
+	resizeType := sizeParts[3]
+
+	if width == 0 && height == 0 {
+		return errors.New("Thumb width and height cannot be zero at the same time.")
+	}
 
 	// fetch the original
 	r, readErr := s.bucket.NewReader(s.ctx, originalKey, nil)
@@ -256,14 +271,27 @@ func (s *System) CreateThumb(originalKey string, thumbKey, thumbSize string, cro
 		return decodeErr
 	}
 
-	// determine crop anchor
-	cropAnchor := imaging.Center
-	if !cropCenter {
-		cropAnchor = imaging.Top
-	}
+	var thumbImg *image.NRGBA
 
-	// create thumb imaging object
-	thumbImg := imaging.Fill(img, width, height, cropAnchor, imaging.CatmullRom)
+	if width == 0 || height == 0 {
+		// force resize preserving aspect ratio
+		thumbImg = imaging.Resize(img, width, height, imaging.CatmullRom)
+	} else {
+		switch resizeType {
+		case "f":
+			// fit
+			thumbImg = imaging.Fit(img, width, height, imaging.CatmullRom)
+		case "t":
+			// fill and crop from top
+			thumbImg = imaging.Fill(img, width, height, imaging.Top, imaging.CatmullRom)
+		case "b":
+			// fill and crop from bottom
+			thumbImg = imaging.Fill(img, width, height, imaging.Bottom, imaging.CatmullRom)
+		default:
+			// fill and crop from center
+			thumbImg = imaging.Fill(img, width, height, imaging.Center, imaging.CatmullRom)
+		}
+	}
 
 	// open a thumb storage writer (aka. prepare for upload)
 	w, writerErr := s.bucket.NewWriter(s.ctx, thumbKey, nil)
@@ -274,7 +302,6 @@ func (s *System) CreateThumb(originalKey string, thumbKey, thumbSize string, cro
 	// thumb encode (aka. upload)
 	if err := imaging.Encode(w, thumbImg, imaging.PNG); err != nil {
 		w.Close()
-
 		return err
 	}