tleyden · tleyden · Dec 12, 2018 · Dec 12, 2018 · Dec 12, 2018 · Dec 12, 2018
diff --git a/convert-pdf.go b/convert-pdf.go
@@ -0,0 +1,77 @@
+package ocrworker
+
+/*	Use this module if you want to call tesseract over
+	pdfsandwich with an image as input file.
+	Useful with big documents.
+
+	Use cases:
+	engine: tesseract with file_type: pdf and preprocessor: convert-pdf
+	engine: sandwich  with file_type: [tif, png, jpg] and preprocessor: convert-pdf
+*/
+
+import (
+	"fmt"
+	"github.com/couchbaselabs/logg"
+	"io/ioutil"
+	"os"
+	"os/exec"
+)
+
+type ConvertPdf struct {
+}
+
+func (c ConvertPdf) preprocess(ocrRequest *OcrRequest) error {
+
+	tmpFileNameInput, err := createTempFileName()
+	tmpFileNameInput = fmt.Sprintf("%s.pdf", tmpFileNameInput)
+	if err != nil {
+		return err
+	}
+	defer os.Remove(tmpFileNameInput)
+
+	tmpFileNameOutput, err := createTempFileName()
+	tmpFileNameOutput = fmt.Sprintf("%s.tif", tmpFileNameOutput)
+	if err != nil {
+		return err
+	}
+	defer os.Remove(tmpFileNameOutput)
+
+	err = saveBytesToFileName(ocrRequest.ImgBytes, tmpFileNameInput)
+	if err != nil {
+		return err
+	}
+
+	logg.LogTo(
+		"PREPROCESSOR_WORKER",
+		"Convert PDF %s -> %s",
+		tmpFileNameInput,
+		tmpFileNameOutput,
+	)
+
+	var gsArgs []string
+	gsArgs = append(gsArgs,
+		"-dQUIET",
+		"-dNOPAUSE",
+		"-dBATCH",
+		"-sOutputFile="+tmpFileNameOutput,
+		"-sDEVICE=tiffg4",
+		tmpFileNameInput,
+	)
+	logg.LogTo("PREPROCESSOR_WORKER", "output: %s", gsArgs)
+
+	out, err := exec.Command("gs", gsArgs...).CombinedOutput()
+	if err != nil {
+		logg.LogFatal("Error running command: %s. out: %s", err, out)
+	}
+	logg.LogTo("PREPROCESSOR_WORKER", "output: %v", string(out))
+
+	// read bytes from output file
+	resultBytes, err := ioutil.ReadFile(tmpFileNameOutput)
+
+	if err != nil {
+		return err
+	}
+	ocrRequest.ImgBytes = resultBytes
+
+	return nil
+}
diff --git a/preprocessor.go b/preprocessor.go
@@ -1,7 +1,8 @@
 package ocrworker
 
-const PREPROCESSOR_IDENTITY = "identity"
-const PREPROCESSOR_STROKE_WIDTH_TRANSFORM = "stroke-width-transform"
+const PreprocessorIdentity = "identity"
+const PreprocessorStrokeWidthTransform = "stroke-width-transform"
+const PreprocessorConvertPdf = "convert-pdf"
 
 type Preprocessor interface {
 	preprocess(ocrRequest *OcrRequest) error

diff --git a/preprocessor_rpc_worker.go b/preprocessor_rpc_worker.go
@@ -26,12 +26,13 @@ const preprocessor_tag = "preprocessor" // TODO: should be unique for each worke
 func NewPreprocessorRpcWorker(rc RabbitConfig, preprocessor string) (*PreprocessorRpcWorker, error) {
 
 	preprocessorMap := make(map[string]Preprocessor)
-	preprocessorMap[PREPROCESSOR_STROKE_WIDTH_TRANSFORM] = StrokeWidthTransformer{}
-	preprocessorMap[PREPROCESSOR_IDENTITY] = IdentityPreprocessor{}
+	preprocessorMap[PreprocessorStrokeWidthTransform] = StrokeWidthTransformer{}
+	preprocessorMap[PreprocessorIdentity] = IdentityPreprocessor{}
+	preprocessorMap[PreprocessorConvertPdf] = ConvertPdf{}
 
 	_, ok := preprocessorMap[preprocessor]
 	if !ok {
-		return nil, fmt.Errorf("No preprocessor found for: %q", preprocessor)
+		return nil, fmt.Errorf("no preprocessor found for: %q", preprocessor)
 	}
 
 	preprocessorRpcWorker := &PreprocessorRpcWorker{
@@ -71,11 +72,11 @@ func (w PreprocessorRpcWorker) Run() error {
 	if err = w.channel.ExchangeDeclare(
 		w.rabbitConfig.Exchange,     // name of the exchange
 		w.rabbitConfig.ExchangeType, // type
-		true,  // durable
-		false, // delete when complete
-		false, // internal
-		false, // noWait
-		nil,   // arguments
+		true,                        // durable
+		false,                       // delete when complete
+		false,                       // internal
+		false,                       // noWait
+		nil,                         // arguments
 	); err != nil {
 		return err
 	}
@@ -100,8 +101,8 @@ func (w PreprocessorRpcWorker) Run() error {
 		queue.Name,              // name of the queue
 		w.bindingKey,            // bindingKey
 		w.rabbitConfig.Exchange, // sourceExchange
-		false, // noWait
-		nil,   // arguments
+		false,                   // noWait
+		nil,                     // arguments
 	); err != nil {
 		return err
 	}
@@ -128,7 +129,7 @@ func (w PreprocessorRpcWorker) Run() error {
 func (w *PreprocessorRpcWorker) Shutdown() error {
 	// will close() the deliveries channel
 	if err := w.channel.Cancel(w.tag, true); err != nil {
-		return fmt.Errorf("Worker cancel failed: %s", err)
+		return fmt.Errorf("worker cancel failed: %s", err)
 	}
 
 	if err := w.conn.Close(); err != nil {
@@ -231,7 +232,7 @@ func (w *PreprocessorRpcWorker) handleDelivery(d amqp.Delivery) error {
 	ocrRequest := OcrRequest{}
 	err := json.Unmarshal(d.Body, &ocrRequest)
 	if err != nil {
-		msg := "Error unmarshaling json: %v.  Error: %v"
+		msg := "Error unmarshalling json: %v.  Error: %v"
 		errMsg := fmt.Sprintf(msg, string(d.Body), err)
 		logg.LogError(fmt.Errorf(errMsg))
 		return err

diff --git a/stroke_width_transform.go b/stroke_width_transform.go
@@ -74,7 +74,7 @@ func (s StrokeWidthTransformer) extractDarkOnLightParam(ocrRequest OcrRequest) s
 	val := "1"
 
 	preprocessorArgs := ocrRequest.PreprocessorArgs
-	swtArgs := preprocessorArgs[PREPROCESSOR_STROKE_WIDTH_TRANSFORM]
+	swtArgs := preprocessorArgs[PreprocessorStrokeWidthTransform]
 	if swtArgs != nil {
 		swtArg, ok := swtArgs.(string)
 		if ok && (swtArg == "0" || swtArg == "1") {