image_resize filter

helper/render.go

@@ -27,6 +27,36 @@ func BackToRoot(curNavPath string) string {
 	return tmpPath
 }
 
+// ResolveNavPath fixes nav target relative to current navigation path
+func ResolveNavPath(target string) string {
+	curNavPath := (*currentContext)["CurrentPath"].(string)
+	if strings.HasPrefix(target, "/") {
+		target = BackToRoot(curNavPath) + target
+	}
+	target = path.Clean(target)
+	return target
+}
+
+// ResolveOutputPath fixes output directory relative to current navigation path
+func ResolveOutputPath(target string) string {
+	if strings.HasPrefix(target, "/") {
+		target = config.Config.Directories.Output + "/" + target
+	} else {
+		target = currentTreeNodeConfig.OutputPath + "/" + target
+	}
+	return path.Clean(target)
+}
+
+// ResolveInputPath fixes input directory relative to current navigation path
+func ResolveInputPath(target string) string {
+	if strings.HasPrefix(target, "/") {
+		target = config.Config.Directories.Input + "/" + target
+	} else {
+		target = currentTreeNodeConfig.InputPath + "/" + target
+	}
+	return path.Clean(target)
+}
+
 // SetTemplateDir sets base directory for searching template files
 func SetTemplateDir(dir string) {
 	templateDir = dir

helper/template_filters.go

@@ -1,11 +1,15 @@
 package helper
 
 import (
+	"errors"
+	"fmt"
 	"io/ioutil"
 	"path"
+	"strconv"
 	"strings"
 
 	"github.com/ddliu/motto"
+	"github.com/disintegration/imaging"
 	"github.com/flosch/pongo2"
 	_ "github.com/flosch/pongo2-addons"
 	_ "github.com/robertkrimen/otto/underscore"
@@ -16,6 +20,17 @@ func init() {
 	if err != nil {
 		panic(err)
 	}
+
+	newFilters := map[string]pongo2.FilterFunction{
+		"image_resize":  ImageResizeFilter,
+		"relative_path": RelativePathFilter,
+	}
+	for name, fn := range newFilters {
+		err := pongo2.RegisterFilter(name, fn)
+		if err != nil {
+			panic(err)
+		}
+	}
 }
 
 // MarkdownFilter is a pongo2 filter, which converts markdown to html
@@ -29,6 +44,88 @@ func MarkdownFilter(in *pongo2.Value, param *pongo2.Value) (*pongo2.Value, *pong
 		nil
 }
 
+type imageParams struct {
+	width    int
+	height   int
+	filename string
+}
+
+func parseImageParams(str string) (*imageParams, error) {
+	if str == "" {
+		return nil, errors.New("missing image parameters")
+	}
+	p := imageParams{}
+	for _, s := range strings.Split(str, ",") {
+		e := strings.Split(s, "=")
+		if len(e) < 2 {
+			return nil, fmt.Errorf("invalid image parameter: %s", s)
+		}
+		var err error
+		switch e[0] {
+		case "w":
+			p.width, err = strconv.Atoi(e[1])
+		case "h":
+			p.height, err = strconv.Atoi(e[1])
+		case "f":
+			p.filename = e[1]
+		default:
+			return nil, fmt.Errorf("invalid image parameter: %s", s)
+		}
+		if err != nil {
+			return nil, fmt.Errorf("could not convert image parameter to correct value type for '%s': %s", s, err)
+		}
+	}
+	return &p, nil
+}
+
+// ImageResizeFilter read the image url and resize parameters and saves the resized image
+// param: w=WITDH,h=HEIGHT
+func ImageResizeFilter(in *pongo2.Value, param *pongo2.Value) (*pongo2.Value, *pongo2.Error) {
+	imgSource := in.String()
+	p, err := parseImageParams(param.String())
+	if err != nil {
+		return nil, &pongo2.Error{
+			Sender:    "filter:image_resize",
+			OrigError: err,
+		}
+	}
+
+	imgSource = ResolveInputPath(imgSource)
+	if p.filename == "" {
+		p.filename = fmt.Sprintf("%dx%d_%s", p.width, p.height, path.Base(imgSource))
+	}
+	imgTarget := ResolveOutputPath(p.filename)
+	Log.Noticef("resizing image from %s to %s", imgSource, imgTarget)
+
+	img, err := imaging.Open(imgSource, imaging.AutoOrientation(true))
+	if err != nil {
+		return nil, &pongo2.Error{
+			Sender:    "filter:image_resize",
+			OrigError: fmt.Errorf("could not open image '%s': %s", imgSource, err),
+		}
+	}
+	img = imaging.Resize(img, p.width, p.height, imaging.Lanczos)
+
+	err = imaging.Save(img, imgTarget)
+	if err != nil {
+		return nil, &pongo2.Error{
+			Sender:    "filter:image_resize",
+			OrigError: fmt.Errorf("could save image '%s': %s", imgTarget, err),
+		}
+	}
+
+	return pongo2.AsValue(ResolveNavPath(p.filename)), nil
+}
+
+// RelativePathFilter returns the relative path to navpoint based on current nav
+func RelativePathFilter(in, param *pongo2.Value) (*pongo2.Value, *pongo2.Error) {
+	return pongo2.AsValue(
+		ResolveNavPath(
+			in.String(),
+		),
+	), nil
+}
+
 // RegisterFilters reads a directory and register filters from files within it
 func RegisterFilters(dir string) {
 	files, err := ioutil.ReadDir(dir)