pdf bad ocr

[mirkop]

Hello,

I'm creating a PDF OCR using tesseract from a tif, but with some files (like fax) the OCR result i complety wrong.
I attach a tif file as sample ..
Can you help me?

Mirko

[Loïc]

Hi,

This file contains different horizontal (204 dpi) & vertical (98 dpi) resolution.

What I can suggest is to resize the image in order to have similar resolution:

Code: Select all

        Dim ResFactor As Single
        Dim Hres, Vres As Single

        Vres = oGdPictureImaging.GetVerticalResolution(m_ImageID)
        Hres = oGdPictureImaging.GetVerticalResolution(m_ImageID)

        ResFactor = Hres / Vres

        If ResFactor <> 1 Then
            Call oGdPictureImaging.Resize(m_ImageID, CInt(oGdPictureImaging.GetWidth(m_ImageID) * ResFactor), oGdPictureImaging.GetHeight(m_ImageID), Drawing2D.InterpolationMode.HighQualityBicubic)
        End If

You should have good OCR improvement with this method.

Best regards,

Loïc

[mirkop]

Hi,

It work fine for tif single page, but it doesn't work for multipage tif. It create one page pdf.
This is my code:

Code: Select all

Single ResFactor;
                Single Hres;
                Single Vres;
                Vres = oGdPictureImaging.GetVerticalResolution(ImageID);
                Hres = oGdPictureImaging.GetHorizontalResolution(ImageID);

                ResFactor = Hres / Vres;

                if (ResFactor != 1)
                    oGdPictureImaging.Resize(ImageID,
                        oGdPictureImaging.GetWidth(ImageID),
                        Convert.ToInt32(oGdPictureImaging.GetHeight(ImageID) * ResFactor),
                      System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic);

                if (oGdPictureImaging.TiffIsMultiPage(ImageID))
                {
                    
                    if (makeSearchable == false)
                        oGdPictureImaging.PdfCreateFromMultipageTIFF(ImageID, filePDF, pdfA, "", "", "", "", "");
                    else
                        oGdPictureImaging.PdfOCRCreateFromMultipageTIFF(ImageID,
                            GetTesseractDictionary(dizionario),
                            _dirOCR, "", filePDF, pdfA, "", "", "", "", "");
                }
                else
                {
                    if (makeSearchable == false)
                        oGdPictureImaging.SaveAsPDF(ImageID, filePDF, pdfA, "", "", "", "", "");
                    else
                        oGdPictureImaging.SaveAsPDFOCR(ImageID, filePDF,
                            GetTesseractDictionary(dizionario),
                            _dirOCR, "", pdfA, "", "", "", "", "");
                }
                oGdPictureImaging.ReleaseGdPictureImage(ImageID);

Mirko

[Loïc]

Hi,

You need to open the multipage tiff for read & write.
For that, just call the

Code: Select all

TiffOpenMultiPageForWrite(True)

before opening a file.

Then, you will have to resize all page in a loop:

Code: Select all

For i = 1 to oGdPictureImagingImaging.TiffGetPageCount(imageid)       
        oGdPictureImagingImaging.TiffSelectPage(imageid, i)
        oGdPictureImagingImaging.Resize(imageid...)
Next i

Let me know if you have other problem with this issue.

Kind regards,

Loïc

[mirkop]

Thank you .. it works fine.

Mirko