HTTP request's "config_vars" without effect when using open-ocr-2 / Tesseract 4.00

[danielpater]

The HTTP request's config_vars property has no effect when using the Docker setup with Docker image tleyden5iwx/open-ocr-2 (Version 2 / Tesseract 4.00).

When using Version 1 based on the original Docker image tleyden5iwx/open-ocr, config_vars property allows to pass command line config arguments like tessedit_char_whitelist to Tesseract. This does not work with tleyden5iwx/open-ocr-2.

Example request allowing only digits as result character set:
$ curl -X POST -H "Content-Type: application/json" -d '{"img_url":"http://bit.ly/ocrimage","engine":"tesseract", "engine_args":{"config_vars":{"tessedit_char_whitelist":"0123456789"}, "psm":"3"}}' http://$DOCKER_HOST:$HTTP_PORT/ocr

Response body with tleyden5iwx/open-ocr:
011 2111 01133126 10031 31 111165 1 01 116 1 1 61 11635 1211 11 116 811111 13126 13 1 1 3 3161 116 31 211113 1131116 1211 1 1 5 5 3711 211 1311 16 112111135 1121 16 0 1 3 001111 053 1 0 311 1121111111161 6113111012813 5111 21 116 11111 161 8001 6 111 116 63211111 16 1 610 1 1121 16 118611 1 1155 31 1 0115 1131 01 1 1 01 31 211113 112111133

Response body with tleyden5iwx/open-ocr-2:
You can create local variables for the pipelines within the template by prefixing the variable name with a "$" sign. Variable names have to be composed of alphanumeric characters and the underscore. In the example below I have used a few variations that work for variable names.

[tleyden]

I think open-ocr must be calling tesseract incorrectly when it comes to newer versions of tesseract

Thinking out loud ... this is the call to tesseract:

open-ocr/tesseract_engine.go

Lines 171 to 175 in d87b7f7

	// build args array
	cflags := engineArgs.Export()
	cmdArgs := []string{inputFilename, tmpOutFileBaseName}
	cmdArgs = append(cmdArgs, cflags...)
	logg.LogTo("OCR_TESSERACT", "cmdArgs: %v", cmdArgs)

and this is how it builds the args:

open-ocr/tesseract_engine.go

Lines 76 to 95 in d87b7f7

	// return a slice that can be passed to tesseract binary as command line
	// args, eg, ["-c", "tessedit_char_whitelist=0123456789", "-c", "foo=bar"]
	func (t TesseractEngineArgs) Export() []string {
	result := []string{}
	for k, v := range t.configVars {
	result = append(result, "-c")
	keyValArg := fmt.Sprintf("%s=%s", k, v)
	result = append(result, keyValArg)
	}
	if t.pageSegMode != "" {
	result = append(result, "-psm")
	result = append(result, t.pageSegMode)
	}
	if t.lang != "" {
	result = append(result, "-l")
	result = append(result, t.lang)
	}
	return result
	}

I wonder if this works for tesseract 4?

-c tessedit_char_whitelist=0123456789