So I have this png image here
and when I try to read it with tesseract on the command line, I get some random character
❯ tesseract Selection_002.png stdout --psm 7
Warning. Invalid resolution 0 dpi. Using 70 instead.
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I'm running tesseract version 4.0.0-beta.1-370-g8b64 on ubuntu.
I would have guessed that this image would be easy to read for tesseract?
I've gone through trying to resize the image and "cleaning" it up but there's no much noise to clean on that. What Am I doing wrong?
Please try inverting the image color. (Black text on white).
I tried with your image as well as inverting the color. Both gave successful results.
Related
I'm trying to convert simple image with numbers to text using https://github.com/tesseract-ocr/tesseract. I compiled latest version from github with Leptonica and other libs required for image process.
My image looks like this:
I'm trying to convert it like this: /usr/local/bin/tesseract '/home/var/img2text/phone.png' out but instead of numbers something like 3m mam. what could be the problem?
The image is small and the quality of it is a little low, try the following:
1- Change its DPI to 300
2- Resize the image 2x and apply Resample interpolation.
3- Make sure it is a B/W image.
Here are some useful links:
https://code.google.com/p/tesseract-ocr/wiki/ImproveQuality
image processing to improve tesseract OCR accuracy
I am attempting to make a very simple label using Libreoffice Draw v 4.0.2.2. The label has not much more to it than regularly spaced lines of centered text
This image will be printed, and I have a fixed size/ppi requirement to ensure appropriate print quality.
I set the page size to my specs, and layout the text as I desire. The print shop takes several image formats including .tiff and .png. When I export the image, a dialog pops up that asks for the image size/ resolution. The given ppi is very low (~40) and I require a minimum of 180ppi. When I enter this, the image size adjusts itself and results in an image that is far too small.
The only solution that appears to be viable is to explode the page size and the drawing text size so it gets shrunk upon export. This is a very imprecise and illogical feature (bug?) of the program that I really wish is a result of my ignorance.
I found a thread in the mailing list which describes this issue exactly. The only answer that is given is essentially "yes, this is ridiculous and doesn't help anybody".
Can anyone give some advice to this? Or at least shed some light on who might need this "feature"?
There is something off about the Export tool of LibreOffice in general. It has been years since it is broken. Taking a screenshot is an alternative, but obviously you cannot control the resolution.
So, a better work around is exporting to SVG, and then convert the SVG to PNG with Inkscape. Once downloaded, convert the file with the following command:
inkscape -z -e out.png -w 1024 in.svg
If you are in Windows (x64), you will need to indicate the full path:
"C:/Program Files/Inkscape/inkscape.exe" -z -e out.png -w 1024 in.svg
If you install the 32 bit version, this should work:
"C:\Program Files (x86)/Inkscape/inkscape.exe" -z -e out.png -w 1024 in.svg
This can be done from inside Libre Office, there is no need to use any external tool. The Export dialog is very confusing, yes; you have to realize that both size and resolution can be set independently.
Select File -> Export -> choose the desired format. The export dialog should appear.
TAKE NOTE of Width and Height. Set the desired resolution; notice how Width and Height change (?). Don't worry, restore Width and Height to your saved values. And that's it. You get a high resolution image with the desired size and DPI.
Libre Draw (the one I'm using anyway) is a vector drawing app - have you asked the print shop if they can use vector formats like eps, pdf? Most should be able to in my experience. Then resolution becomes irrelevant.
-Terry
I am using tesseract open source engine for OCR to read text from image.
But I didn't get 100% result for a single time. Please give your suggestions about quality improvement for OCR using tesseract.
Thanks
here is how to get best result from tesseract
Please make sure that you have done preprocessing on image. OVR will produce best results for the images which have following properties:
fix DPI (if needed) 300 DPI is minimum
fix text size (e.g. 12 pt should be ok)
try to fix text lines (deskew and dewarp text)
try to fix illumination of image (e.g. no dark part of image
binarize and de-noise image
https://groups.google.com/forum/?fromgroups=#!topic/tesseract-ocr/g5aE_OvgyTU
Am trying to extract data from reciepts and bills using Tessaract , am using tesseract 3.02 version .
am using only english data , Still the output accuracy is about 60%.
Is there any trained data available which i just replace in tessdata folder
This is the image nicky provided as a "typical example file":
Looking at it I'd clearly say: "Forget it, nicky! You cannot train Tesseract to recognize 100% of text from this type of image!"
However, you could train yourself to make better photos with your iPhone 3GS (that's the device which was used for the example pictures) from such type of receipts. Here are a few tips:
Don't use a dark background. Use white instead.
Don't let the receipt paper crumble. Straighten it out.
Don't place the receipt loosely on an uneven underground. Fix it to a flat surface:
Either place it on a white sheet of paper and put a glas platen over it.
Or use some glue and glue it flat on a white sheet of paper without any bend-up edges or corners.
Don't use a low resolution like just 640x480 pixels (as the example picture has). Use a higher one, such as 1280x960 pixels instead.
Don't use standard exposure. Set the camera to use extremely high contrast. You want the letters to be black and the white background to be really white (you don't need the grays in the picture...)
Try to make it so that any character of a 10-12 pt font uses about 24-30 pixels in height (that is, make the image to be about 300 dpi for 100% zoom).
That said, something like the following ImageMagick command will probably increase Tesseract's recognition rate by some degree:
convert \
http://i.stack.imgur.com/q3Ad4.jpg \
-colorspace gray \
-rotate 90 \
-crop 260x540+110+75 +repage \
-scale 166% \
-normalize \
-colors 32 \
out1.png
It produces the following output:
You could even add something like -threshold 30% as the last commandline option to above command to get this:
(You should play a bit with some variations to the 30% value to tweak the result... I don't have the time for this.)
Taking accurate info from a receipt is not impossible with tesseract. You will need to add image filters and some other tools such as OpenCV, NumPy ImageMagick alongside Tesseract. There was a presentation at PyCon 2013 by Franck Chastagnol where he describes how his company did it.
Here is the link:
http://pyvideo.org/video/1702/building-an-image-processing-pipeline-with-python
You can get a much cleaner post-processed image before using Tesseract to OCR the text. Try using the Background Surface Thresholding (BST) technique rather than other simple thresholding methods. You can find a white paper on the subject here.
There is an implementation of BST for OpenCV that works pretty well https://stackoverflow.com/a/22127181/3475075
i needed exactly the same thing and i tried some image optimisations to improve the output
you can find my experiment with tessaract here
https://github.com/aryansbtloe/ExperimentWithTesseract
While trying to run this command:
tesseract bond111.tif bond111 batch.nochop makebox
I get the next error
Error in pixReadFromTiffStream: spp not in set {1,3}
Error in pixReadStreamTiff: pix not read
Error in pixReadTiff: pix not read
Assuming that spp not in set is the main error here, what does it mean?
At first it had trouble because the bpp was higher than 24 so I reduced it using Gimp but that did not resolve the issue.
It probably means your TIFF image has an alpha channel and therefore the underlying Leptonica library used by Tesseract doesn't support it. If you're using Imagemagick then be aware that operations such as -draw can cause alpha channels to be added. If you're using convert in your workflow and want to remove the channel again immediately, flatten the image before writing by adding -background white -flatten +matte before the output filename, e.g.:
convert input.tiff -fill white -draw 'rectangle 10,10 20,20' -background white -flatten +matte output.tiff
Tesseract (well, Leptonica) accepts PNGs these days and is less picky about them, so it might be easier to migrate your workflow to PNG anyway.
Sources: magick-users mailing list posting; tesseract-ocr mailing list posting
Thanks for your post ZakW, you pointed me to the right direction.
Anyhow i also needed to set '-depth 8'. Quality was not good enough for OCR, whatever I tried.
What worked for me is this solution:
ghostscript -o document.tiff -sDEVICE=tiffgray -r720x720 -g6120x7920 -sCompression=lzw document.pdf
tesseract document.tiff document -l deu
vim document.txt
This way I got perfect text with Umlauts in german.
Adjusting the conversion to the following line did help me.
convert -density 300 input.pdf -depth 8 -background white -alpha Off output.tiff
Note that the other answers did not work for me since they use the deprecated +matte flag instead of -alpha Off.
You can try using the command 'tiffinfo' provided by libtiff_tools to verify the TIFF format of your src image. A number of TIFF formats exist, with different values for Bits-per-pixel (bpp) and Samples-per-pixel (spp).
Error in pixReadFromTiffStream: spp not in set {1,3,4}
An 'spp' value of 2 is invalid for TIFF.
I solved the problem by saving directly to TIFF format from Gimp, instead of converting from .png to .tif using ImageMagick's 'convert'.
See also: TIFF format