Hello,
I'm loosing my hair on coordinates conversion and image extraction.
Here is what I'm trying to do :
I want to perform keyword search on non-searchable pdf or pdfs where
text layer is not well positioned behind images (and then underline the
results using annots) using PDFBOX and an OCR:
I've extended printImageLocation the following way :
On a given page I extract all images and generate png images with JAI
for better quality (tried getting a sole image for the whole page but
results are not good enough with the OCR due to layout issues I think,
with JAI I expect to be able to posterize, reduce noise if necessary,
etc...to make the ocr happy).
I externally run an ocr on them (ocropus/tesseract. it's c++, so I have
some "Process p = Runtime.getRuntime().exec(cmd); " code) which
produces hOCR files giving text and coordinates for each characters.
I'm then able to determine the coordinates of a keyword parsing the
hOCR file.
At this point, I have the coordinates of the keyword in the image, the
position of the image on the page and the size of the image.
I then try to "translate to" coordinates in the pdf page from the ones I
have got from the parsed image.
First I invert the bounding box as the OCR gives me a UpperLeft/
LowerRight couple of points.
then ...I'm stucked : I expected the origin to be lowerleft in a pdf
page but it seems to be upperLeft here.
and to be honest, I hardly figure out which corner of the image is used
to determine its location and what is the metric used.
Inside the image, I retrieve coordinates in dot.
For example, here are the images I've found :
[I0] at 571.26746,71.80139 size=796.0658,93.23215 (small logo)
[I1] at 368.0984,85.12024 size=92.90973,196.4537 (small logo)
[I2] at 583.11694,707.5416 size=12841.42,15587.612 (the scanned article)
[I3] at 176.53192,341.2494 size=402.6675,1046.7035 (image attached to
the article)
visually, [I0] is upperLeft, [I1] is at [I0] right side, [I3] is upper
right but below [I0] and i1 line.
[I2] is the "body" of the page actually a press article, where I find
the keyword's occurences.
here is a set of coordinates retrieved from the ocr processing (upper
left / lower right):
keyword: (2056.0/2484.0) (2193.0/2501.0)
which gives (lower left / upper right):
(2056.0/2501.0) (2193.0/2484.0)
here are the coordinates of the same occurence in the pdf (the result I
would find after a conversion lowerleft / upper right. Provided here
parsing the text layer hopefully well positionned) :
START : String[ xy=511.5022,665.7338 fontsize=33.0 xscale=0.24686399
yscale=0.225744 height=5.579715 space=2.2647307 width=128.40302] = keyword
END : String[ xy=511.5022,665.7338 fontsize=33.0 xscale=0.24686399
yscale=0.225744 height=5.579715 space=2.2647307 width=128.40302] = keyword
--------->keyword : 1790.4882,2322.2808, 1881.345,2348.561 (the
bounding box converted in a suitable metric system to put annotations on it)
I guess I have to set up a transformation matrix but I don't know what
parameters I have to take into accounts (and if they are available in a
way or another !).
Could someone provide some advices ?
Thanks
fb.
