Thanks all for your answers! @Mox Betex
> Did you train Tesseract? > @ElGato ElMago > Those images and fonts obviously are not for OCR. Need to improve images > and train fonts. No, I use tesseract vanilla, only binary tuning parameters. I'd like to avoid training my own model at first, but I add it to my "things to explore" list. @ElGato ElMago > Do you only need to read temparatures? Then some pattern recognition > method in OpenCV might be easier to work with. > Yes, only the numbers on the right are needed. Actually, this looks to be a very good idea (in that results may be more predictible), it's worth a try. @Lorenzo Bolzani, thanks for your very detailed answer! This is valuable stuff that will help me iterate, for sure. I'll keep you posted of my progress, Cheers Nicolas Le mer. 19 juin 2019 à 11:49, Lorenzo Bolzani <[email protected]> a écrit : > Hi Nicolas, I think what you did is good, you just need to play with > pre-processing more. > > I usually process the images with Gimp until I can get a good results, > then I try to do the same processing with opencv/PIL. > > You do not strictly need to threshold the image, a very very strong > contrast is enough and may work better. Play with curves, histogram > normalization (cv2.normalize(MINMAX), cv2.equalizeHist, > PIL.rescale_intensity, PIL.autocontrast), multiply the image with itself, > sharpen. Gaussian difference could also give good results. A little > blur/denoise should remove the small dust or close/erode after thresholding. > > You can try CLAHE to normalize the illumination, this looks like a big > problem. The left part is terrible, barely readable, maybe focus is not > flat on the screen? The "EXT" text is very hard to recover. Try to get a > better starting image if possible. The screen contrast in the other shots > is very good, try to understand why it gets lost. Maybe the viewing angle? > Camera settings? LCD is bad when seen from above? Maybe side/bottom may > work better or a few degrees more tilted? Too much light washing out the > black text (from the leds?)? > > See the attached script for some ideas and examples (not fine tuned for > this image, I used it for something else). Try the other one to understand > where the text is coming from (I think you need libtesseract-dev to install > tesserocr). > > I would crop the image into five different lines, process each one > individually, especially for adaptive stuff, OTSU, CLAHE, etc. You could > also separate the text part (left) from the numbers and process them > separately. Do you really need the text on the right? Isn't it fixed? > > You do not need so much resolution, downscale the text so that each line > is about 30/50px, try different the scales that works best. Usually it is > better to downscale after the pre-processing. > I think dpi are used only of the page segmentation part, I never use them, > I downscale the text and use single lines. > > I do not think you need to fine tune the model right now, try as much as > possible not to do it. If you cannot get good results with hand-tuned gimp > pre-processing of individual lines consider fine tuning on this font. The > big advantage of fine tuning is also that you can limit the set of > characters. There is a digits only model around, you may try that on the > numbers part. > > This is what I get from tesseract: > > $ tesseract -l eng --psm 6 step5-threshold.jpeg - > YY ALEIRES MESUREES > EXTER | EUR 21.9% > SHEE ANT 24.2% > EG EA 2a .e%T > HBETTOUE EAD ITNT 22.4% > > Downscale the image to width 400: > > YRLEURS MESUREES : > EETERIEDR 21 .9¢ > SIE AMT 24.2% > CEG EAU 20.0% > SETOUR EAD INT 22.4% > > This is almost perfect, but it is quite fragile, using 500 I get this: > > YALEURS MESUREES : > ENTER EUR 21.9% > SAEIEE AMT 24.2% > EG EA 26.8% > SETOUR EAD INT 22.4% > > Cutting out the celsius unit gives a little better results. Also a darker > threshold, where the characters are more connected seems to work better. > Maybe the font need some fine tuning, the third line with the zeros is the > main problem. Cutting individual lines or numbers does not help. > > I started over with gimp from step0 focusing on numbers and I get the > attached image, with this one the results are more stable with different > image downscales (400, 500, 600). Maybe the third line was just a bad case. > > VAIL FURS NMESUREES > XTE (EI IF 21.9% > Sead T 24.2% > EAU 20.0% > EFAS INT 22.94% > > > Bye > > Lorenzo > > > Il giorno mar 18 giu 2019 alle ore 21:45 Nicolas Colomer < > [email protected]> ha scritto: > >> Hello tesseract community, >> >> I'm looking for help about one OCR use case I try to achieve using a >> combination of python, opencv and tesseract. >> The goal is to recurrently take a picture of the screen of my heat pump >> controller to extract the metrology it exposes. >> It's a (funny) DIY project with mix of electronics, raspberry pi zero and >> a pi camera stuff, 3d-printed support, etc. >> Here is a photo of the project in its current state: >> >> [image: IMG_3314.jpg][image: IMG_3312.jpg] >> >> My problem is that the result is quite deceiving and not usable for now. >> I tried various hardware (camera focus, lighting) and software (image >> processing algorithm and filters) attempts, with help of various internet >> resources (tesseract doc >> <https://github.com/tesseract-ocr/tesseract/wiki/ImproveQuality>, opencv >> doc <https://docs.opencv.org/3.4.4/d7/d4d/tutorial_py_thresholding.html>, >> ocr blog >> <https://www.freecodecamp.org/news/getting-started-with-tesseract-part-ii-f7f9a0899b3f/> >> posts >> <https://www.pyimagesearch.com/2018/09/17/opencv-ocr-and-text-recognition-with-tesseract/>), >> with no convincing success. >> >> From this (sized down, see step0.jpeg attachement for original picture) >> image: >> >> [image: from.jpeg] >> >> >> I end with this: >> >> >> [image: result.jpeg] >> >> >> >> Finally, when I apply tesseract, best result I could obtain is: >> >> . YALEURS MESUREES >> >> EATER PEUF 21.a% >> Se PAM 24.2% >> SG EAL Be Las >> ECT OLIF: EAW INT 22.4% >> >> 7 at >> >> What I don't understand from this point: >> >> - the image looks quite readable to me, especially the number part >> - why is there a "7 at" reliquat at the end? >> - I tried to extract each line independently, no improvement >> - I tried to add white border, it doesn't help >> - I tried both tesseract 3 and tesseract 4 (LSTM), no significant >> difference >> >> You'll find attached the pipeline.py file that contains the image >> preparation pipeline I use. >> It is implemented in python3 with opencv (via opencv-python-headless >> 3.4.4.19) and tesseract (via pytesseract 0.2.6). >> >> In addition, I attached the image output of each steps: >> >> - step0.jpeg: original file >> - step1-blur.jpeg: apply gaussian blur filter (helps later when >> applying adaptive threshold) >> - step2-rotate.jpeg: rotate the image 180° >> - step3-crop.jpeg: select only the interesting part >> - step4-perspective.jpeg: transform the image to "flatten" (ie. >> de-perspective) it >> - step5-threshold.jpeg: apply adaptive threshold filter >> >> I think the problem is elsewhere in my image preparation pipeline and >> related to output quality, but I can't figure out what is causing poor >> results and how to improve it. >> >> Any thoughts or guidances? >> >> Thanks for your help, >> Nicolas >> >> -- >> You received this message because you are subscribed to the Google Groups >> "tesseract-ocr" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at https://groups.google.com/group/tesseract-ocr. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/tesseract-ocr/e5006f70-5c86-4c12-a115-b406edb12432%40googlegroups.com >> <https://groups.google.com/d/msgid/tesseract-ocr/e5006f70-5c86-4c12-a115-b406edb12432%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> For more options, visit https://groups.google.com/d/optout. >> > -- > You received this message because you are subscribed to a topic in the > Google Groups "tesseract-ocr" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/tesseract-ocr/PohqMCLBc0g/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/tesseract-ocr. > To view this discussion on the web visit > https://groups.google.com/d/msgid/tesseract-ocr/CAMgOLLzyJiiwaA_x9sUqaqHpuOGG%3DKCNs4jYpRU59bROxcn_tw%40mail.gmail.com > <https://groups.google.com/d/msgid/tesseract-ocr/CAMgOLLzyJiiwaA_x9sUqaqHpuOGG%3DKCNs4jYpRU59bROxcn_tw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "tesseract-ocr" group. 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