Add barcode detection to OCR #651
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- The barcode detection routine tries multiple times (seven to be
precise) to find a code by applying preprocessing the image with the
following filters:
1. Preserve luminance channel
2. Gaussian blur (pre)
3. Parametrizable Binary filter (this is the filter adjusted on every
iteration)
4. [Dilatation & Erosion](https://docs.opencv.org/4.x/db/df6/tutorial_erosion_dilatation.html)
5. 2x Resize
6. 1/2 downsize with linear interpolation
7. Gaussian blur (post)
And appends the detected Code at the end of the OCR scan for the
image.
Rewritten opencv & numpy based image processing filters with Pillow instead. It's a bit slower but it reduces the dependencies to only `libzbar0`.
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Hi @josegomezr and thanks for your PR. First of all I want to apologize for the late reply and thank you for a very interesting addition. I'm fine with the changes overall, I think the main problem has to do with Would you be up to add a setting along the lines of
and then only doing the detection if that setting is enabled? I will leave other comments inline. |
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| def extract_barcodes(self, image): |
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- I'd appreciate adding type hints here. Assuming
imageis aPIL.Imageand the return type is astr? - (minor) This being public it would be great to add a docstring saying what it does, since at first glance I wouldn't necessarily expect this to return text. (Perhaps
extract_text_from_barcodesis more appropiate?
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| return stringify(text) | |||
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| class ZBarDetectorService(object): | |||
| THRESHOLDS = list(range(32, 230, 32)) | |||
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Would you be able to document where these values come from and what they represent?
| results = pyzbar.decode(image) | ||
| # Found it at first try | ||
| if len(results) > 0: | ||
| log.info("OCR: zbar found (%d) results at first shot", len(results)) |
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(minor thing but) I'd lower all of the logging calls to log.debug.
| @@ -45,6 +48,81 @@ def extract_ocr_text(self, data, languages=None): | |||
| return stringify(text) | |||
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| class ZBarDetectorService(object): | |||
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- It would be great to have a few testcases for this
LocalOCRServicecan now detect 1D barcodes and QR Codes via pyzbar.In our investigations we've realized that QR detection can be impaired if the QR Code contain artifacts/noise within the code. We've included a parametrizable processing pipeline to minimize artifacts and improve the scanner performance.
Before (not detected by zbar):
After (detected):
The results of
pyzbarare appended at the end of the OCR output in the form of:Note: result extracted from the sample images above
We have some preliminary timings as well as part of this change. In a best-case scenario (pyzbar finds codes at first try) it'll take ~450ms more than current master, and if it needs to go over the processing pipeline every attempt takes ~1.5s.
Using
python-opencvand numpy improve the speed of the image filters, but we wanted to keep the changes at minimum first.Open Questions: