the question with get_textpage_ocr DPI

[xiaolibuzai-ovo]

I used different DPIs, but it seems that I got the same coordinates. Is this reasonable? Doesn't DPI affect the coordinate positions? Or is there some kind of conversion applied to the results?

code:

docs=pymupdf.open("1.pdf")
page=docs[1]
gt = page.get_textpage_ocr(flags=0,full=True,dpi=150,language='eng')
blocks=page.get_text("dict",textpage=gt)["blocks"]
with open('blocks-test.json', 'w') as f:
    json.dump(blocks, f, indent=4)  

gt = page.get_textpage_ocr(flags=0,full=True,dpi=300,language='eng')
blocks=page.get_text("dict",textpage=gt)["blocks"]
with open('blocks1-test.json', 'w') as f:
    json.dump(blocks, f, indent=4) 

result:

thanks for u help!

[JorjMcKie]

Or is there some kind of conversion applied to the results?

Of course - this is a must! The positions of text on the page cannot depend on the precision by which it is detected. Detection precision is the only sense in life of DPI.

[xiaolibuzai-ovo]

May I ask what this conversion rule is? In other words, how can I obtain the original OCR coordinates? Or how do the coordinates obtained from pdmupdf get_text('dict') correspond to the OCR coordinates?

[JorjMcKie]

When making the pixmap from the original page, it will have a Pixmap.irect. Coordinate transformation from that IRect to the page rectangle is done by the matrix created by method torect.

[xiaolibuzai-ovo]

So, is there a good way to convert the coordinates from PyMuPDF to the original OCR coordinates, assuming the DPI used is 1600?