From fa4f48ad54ec94c222269d335d40b21becff92a4 Mon Sep 17 00:00:00 2001
From: Nick White <git@njw.name>
Date: Tue, 23 Mar 2021 11:14:35 +0000
Subject: hocr: Add ability to specify a custom image path for hocr line
 extraction, and use it in extracthocrlines

---
 cmd/extracthocrlines/main.go | 13 ++++++++++--
 pkg/hocr/hocr.go             | 10 ---------
 pkg/hocr/lines.go            | 48 ++++++++++++++++++++++++++++++++++++++------
 3 files changed, 53 insertions(+), 18 deletions(-)

diff --git a/cmd/extracthocrlines/main.go b/cmd/extracthocrlines/main.go
index d765875..fa5ef28 100644
--- a/cmd/extracthocrlines/main.go
+++ b/cmd/extracthocrlines/main.go
@@ -14,12 +14,13 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"rescribe.xyz/utils/pkg/hocr"
 	"rescribe.xyz/utils/pkg/line"
 )
 
-const usage = `Usage: extracthocrlines file.hocr [file.hocr]
+const usage = `Usage: extracthocrlines [-d] [-e] file.hocr [file.hocr]
 
 Copies the text and corresponding image section for each line
 of a HOCR file into separate files, which is useful for OCR
@@ -64,6 +65,7 @@ func main() {
 		flag.PrintDefaults()
 	}
 	dir := flag.String("d", ".", "Directory to save lines in")
+	embeddedimgpath := flag.Bool("e", false, "Use image path embedded in hOCR (rather than the path of the .hocr file with a .png suffix)")
 	flag.Parse()
 	if flag.NArg() < 1 {
 		flag.Usage()
@@ -71,7 +73,14 @@ func main() {
 	}
 
 	for _, f := range flag.Args() {
-		newlines, err := hocr.GetLineDetails(f)
+		var err error
+		var newlines line.Details
+		if *embeddedimgpath {
+			newlines, err = hocr.GetLineDetails(f)
+		} else {
+			imgName := strings.TrimSuffix(f, ".hocr") + ".png"
+			newlines, err = hocr.GetLineDetailsCustomImg(f, imgName)
+		}
 		if err != nil {
 			log.Fatal(err)
 		}
diff --git a/pkg/hocr/hocr.go b/pkg/hocr/hocr.go
index 6cd1df1..e84c2b1 100644
--- a/pkg/hocr/hocr.go
+++ b/pkg/hocr/hocr.go
@@ -58,16 +58,6 @@ func wordConf(s string) (float64, error) {
 	return strconv.ParseFloat(conf[1], 64)
 }
 
-// Returns the image path for a page from a ocr_page title
-func imagePath(s string) (string, error) {
-	re, err := regexp.Compile(`image ["']([^"']+)["']`)
-	if err != nil {
-		return "", err
-	}
-	m := re.FindStringSubmatch(s)
-	return m[1], nil
-}
-
 // BoxCoords parses bbox coordinate strings
 func BoxCoords(s string) ([4]int, error) {
 	var coords [4]int
diff --git a/pkg/hocr/lines.go b/pkg/hocr/lines.go
index 1c759e0..5794243 100644
--- a/pkg/hocr/lines.go
+++ b/pkg/hocr/lines.go
@@ -16,11 +16,22 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"
 
 	"rescribe.xyz/utils/pkg/line"
 )
 
+// Returns the image path for a page from a ocr_page title
+func imagePathFromTitle(s string) (string, error) {
+	re, err := regexp.Compile(`image ["']([^"']+)["']`)
+	if err != nil {
+		return "", err
+	}
+	m := re.FindStringSubmatch(s)
+	return m[1], nil
+}
+
 // LineText extracts the text from an OcrLine
 func LineText(l OcrLine) string {
 	linetext := ""
@@ -54,11 +65,17 @@ func LineText(l OcrLine) string {
 	return linetext
 }
 
-func parseLineDetails(h Hocr, dir string) (line.Details, error) {
+// parseLineDetails parses a Hocr struct into a line.Details
+// struct, including extracted image segments for each line.
+// The image location is taken from imgPath, which can either
+// be imagePathFromTitle (see above) which loads the image
+// path embedded in the title attribute of a hocr page, or
+// a custom handler.
+func parseLineDetails(h Hocr, dir string, imgPath func(string) (string, error)) (line.Details, error) {
 	lines := make(line.Details, 0)
 
 	for _, p := range h.Pages {
-		imgpath, err := imagePath(p.Title)
+		imgpath, err := imgPath(p.Title)
 		if err != nil {
 			return lines, err
 		}
@@ -68,7 +85,7 @@ func parseLineDetails(h Hocr, dir string) (line.Details, error) {
 		var gray *image.Gray
 		pngf, err := os.Open(imgpath)
 		if err != nil {
-			fmt.Fprintf(os.Stderr, "Warning: error opening image %s: %v", imgpath, err)
+			fmt.Fprintf(os.Stderr, "Warning: error opening image %s: %v\n", imgpath, err)
 		}
 		defer pngf.Close()
 		img, _, err = image.Decode(pngf)
@@ -99,7 +116,7 @@ func parseLineDetails(h Hocr, dir string) (line.Details, error) {
 			ln.Name = l.Id
 			ln.Avgconf = (totalconf / float64(num)) / 100
 			ln.Text = LineText(l)
-			imgpath, err := imagePath(p.Title)
+			imgpath, err := imgPath(p.Title)
 			if err != nil {
 				return lines, err
 			}
@@ -131,7 +148,26 @@ func GetLineDetails(hocrfn string) (line.Details, error) {
 		return newlines, err
 	}
 
-	return parseLineDetails(h, filepath.Dir(hocrfn))
+	return parseLineDetails(h, filepath.Dir(hocrfn), imagePathFromTitle)
+}
+
+// GetLineDetailsCustomImg is a variant of GetLineDetails that
+// uses a provided image path for line image extracts, rather
+// than the image name embedded in the .hocr
+func GetLineDetailsCustomImg(hocrfn string, imgfn string) (line.Details, error) {
+	var newlines line.Details
+
+	file, err := ioutil.ReadFile(hocrfn)
+	if err != nil {
+		return newlines, err
+	}
+
+	h, err := Parse(file)
+	if err != nil {
+		return newlines, err
+	}
+
+	return parseLineDetails(h, filepath.Dir(hocrfn), func(s string) (string, error) {return imgfn, nil})
 }
 
 // GetLineBasics parses a hocr file and returns a corresponding
@@ -149,5 +185,5 @@ func GetLineBasics(hocrfn string) (line.Details, error) {
 		return newlines, err
 	}
 
-	return parseLineDetails(h, filepath.Dir(hocrfn))
+	return parseLineDetails(h, filepath.Dir(hocrfn), imagePathFromTitle)
 }
-- 
cgit v1.2.1-24-ge1ad