Dear Merlijn, Kindly reply to my previous mail.
Thanks and Regards, Subramanyam On Saturday, April 17, 2021 at 11:32:31 PM UTC+5:30 Sharp Subbu wrote: > Dear Merlijn, > > Thank you for your efforts in providing the files "Samle-out.pdf" and > "Samle-out.pdf2". > I have checked these files. The file Samle-out2.pdf highly compressed with > good quality. > Kindly share the soiurce code or the tools that you have used to generate > the file "Samle-out2.pdf". > Kindly let us know that whether i can use your source code or tools on > Windows 10 PC. > > Thanks and Regards, > Subramanyam > On Wednesday, April 14, 2021 at 10:21:14 PM UTC+5:30 Merlijn Wajer wrote: > >> Hi, >> >> On 14/04/2021 15:26, Sharp Subbu wrote: >> > Dear Merlijn, >> > >> > Thank you very much for your reply. >> > We are doing feasibility study on using Tesseract OCR featurs in our >> > project on Windows 10 English 32/64-bit OS. >> > As part of this study, i am trying to find that is it possible to >> compress >> > / reduce the size of the pdf file created by Tesseract OCR >> (CommandLine: > >> > Tesseract input.tif outputFile pdf). >> > To find answer for this question, I have checked tesseract forums, and >> > Tesseract APIs. I did not find any related information. Hence, I have >> > posted the same question in Tesseract Google forums. >> > Regarding this, i received nice reply from you. Thank you very much for >> > that. >> > Firstly, clarify that is Tesseract OCR API supports reducing / >> compressing >> > the OCRed pdf file. Is this support present or not in Tesseract OCR >> sourc >> > code. >> > >> > Kindly fin dthe attached sample pdf file "Sample.pdf" for your >> reference. >> > Kindly compress it and send the compressed pdf file. >> >> Please see attached 'sample-out.pdf' (compression ratio ~3.5), and >> 'sample-out2.pdf' (compression ratio ~7.5). >> >> I also generated one other PDF which illustrates how the compression >> works, rather than being actually compressed, but that file is not >> attached due to file size reasons (~460KB). You can that file (plus the >> other two files) here: https://archive.org/~merlijn/tmp/mrc-pdf/ >> >> Please see the commands I used: >> >> 1. Extract image from PDF (not necessary if you start with an image, >> even better to start with the image and not have Tesseract generate the >> PDF) >> >> > $ pdfimages -all /tmp/Sample.pdf /tmp/sample >> >> 2. OCR: >> >> > $ tesseract /tmp/sample-000.jpg - hocr > /tmp/sample-000.hocr.html >> >> 3. Create PDF (dpi taken from JPEG image): >> >> > $ PATH=$PATH:/home/merlijn/archive/pdf/bin recode_pdf --from-imagestack >> /tmp/sample-000.jpg --hocr-file /tmp/sample-000.hocr.html -o >> /tmp/sample-out.pdf -m 2 -v --dpi 200 >> > [...] >> > Processed 1 pages at 1.80 seconds/page >> > Compression ratio: 3.677732 >> >> 4. Create more compressed PDF (ditto for dpi): >> >> > $ PATH=$PATH:/home/merlijn/archive/pdf/bin recode_pdf --from-imagestack >> /tmp/sample-000.jpg --hocr-file /tmp/sample-000.hocr.html -o >> /tmp/sample-out2.pdf -m 2 --dpi 200 --bg-downsample 3 -v >> > [...] >> > Processed 1 pages at 1.59 seconds/page >> > Compression ratio: 7.581879 >> >> Size comparison: >> >> > $ ls -lsh /tmp/sample-out*.pdf /tmp/Sample.pdf >> > 40K -rw-r--r-- 1 merlijn merlijn 38K Apr 14 18:08 /tmp/sample-out2.pdf >> > 80K -rw-r--r-- 1 merlijn merlijn 79K Apr 14 18:11 /tmp/sample-out.pdf >> > 296K -rw-r--r-- 1 merlijn merlijn 293K Apr 14 17:56 /tmp/Sample.pdf >> >> Note that: >> >> 1. Compression is not lossless, but text should nevertheless be quite >> sharp. >> 2. I run Tesseract on the image in the PDF, so for your purposes you >> might want to instead generate hOCR from the image and let 'recode_pdf' >> make the PDF for you (it's pretty much the same code that Tesseract uses). >> 3. The mask in the PDF is encoded with 'ccitt' and not 'jbig2', which >> would give you slightly better compression still. (This is a bug in >> mupdf which will be fixed in the next mupdf release, I have a patched >> version somewhere, but not at hand) >> 4. I have only tested this on Linux. >> 5. The above run uses Kakadu for JPEG2000 compression, but you could >> also use Grok [0] or OpenJPEG [1] (OpenJPEG already works as per my >> previous email). >> >> Finally, for some reason it looks like the PDFs created with the recode >> tool actually look better than the sample you sent me -- I think that is >> because yours suffers from JPEG artifacts which gets mostly cancelled >> out by the mask technique that MRC employs. >> >> If this looks like something you might want to use, we could talk >> off-list about how to make it works on Windows, to not bother the list >> with details not relevant to Tesseract. >> >> Cheers, >> Merlijn >> >> [0] https://github.com/GrokImageCompression/grok/ >> [1] https://www.openjpeg.org >> >> > Thank you very much for your nice help. >> > Subramanyam >> > >> > >> > On Wednesday, April 14, 2021 at 6:27:43 PM UTC+5:30 Merlijn Wajer wrote: >> > >> >> Hi, >> >> >> >> On 14/04/2021 13:52, Sharp Subbu wrote: >> >>> Dear friends, >> >>> >> >>> Kindly guide/help us to find solution for the below point: >> >>> ============================= >> >>> How to reduce the size of a OCRed pdf file using Tesseract OCR APIs. >> >>> =============================== >> >> >> >> Not sure exactly what use case you have in mind (OS, etc), but I have >> a >> >> suggestion, as I dealt with this in the recent past. >> >> >> >> I developed something similar to the foxit/luratech "PDF compression", >> >> in Python and it is entirely open source. It uses the Tesseract hOCR >> >> result files. The can lead to 3-15x compression ratios (sometimes >> more, >> >> depending on the image formats that you use). >> >> >> >> It converts images to JPEG2000 for best compression (but slower >> loading >> >> times) and also attempts to create a "foreground", "background" and >> >> "mask" image (Mixed Raster Content [0]), which can significantly >> improve >> >> compression. It inserts a text layer just like Tesseract does (the >> code >> >> is a port of Tesseract's C++). >> >> >> >> Here is some info [1], and here is the source code [2]. >> >> >> >> There is a "openjpeg-wip" branch that can use OpenJPEG instead of >> Kakadu >> >> for image compression. >> >> >> >> Example usage to create a PDF from a set of images: >> >> >> >> recode_pdf --from-imagestack 'images/*.jp2' --hocr-file >> >> combined_tesseract_results.html -o out.pdf -v --use-openjpeg -m 2 >> >> >> >> There is also the --from-pdf option instead of --from-imagestack, but >> >> that has only seen light testing. >> >> >> >> You can combine the hOCR result files using hocr-combine-stream [3] >> >> >> >> If this suits your use case, I'd be happy to help/assist here or off >> >> list. There aren't many users of the software yet (the same offer >> >> extends for others reading this list). If you have an example PDF that >> >> you can send me, I'd be happy to try to send you a compressed PDF >> back. >> >> >> >> Cheers, >> >> Merlijn >> >> >> >> >> >> [0] https://en.wikipedia.org/wiki/Mixed_raster_content >> >> [1] https://archive.org/~merlijn/projects/archive-pdf-tools/index.html >> >> [2] https://git.archive.org/merlijn/archive-pdf-tools >> >> [3] >> >> >> >> >> https://git.archive.org/merlijn/archive-hocr-tools/-/blob/master/bin/hocr-combine-stream >> >> >> >> > >> >> -- 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 tesseract-ocr+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/tesseract-ocr/8ddafbd4-437b-40b2-b98c-c88e63d5575an%40googlegroups.com.
