[gdal-dev] geospatialPDF DPI and EXTRA_IMAGES

[Even Rouault]

Le mercredi 25 mai 2016 16:46:10, Luca Delucchi a écrit :
> On 19 May 2015 at 10:37, Even Rouault <even.rouault at spatialys.com> wrote:
> > Luca,
> 
> Hi Even,
> 
> > According to the doc, "x and y are in user units from the lower left
> > corner of the page"
> 
> I have other two questions:
> - is it possible to calculate the maximum x and y in user units? I
> tried using the difference between maximum x and y coordinates but
> this doesn't work...
> - what are the DPI useful for? We tried to change the value but we
> cannot see big changes, sometimes the DPI changed the extend of the
> resulting PDF

The following extract from the driver should hopefully answer your questions :

    double dfUserUnit = dfDPI * USER_UNIT_IN_INCH;
    double dfWidthInUserUnit = nWidth / dfUserUnit + sMargins.nLeft + sMargins.nRight;
    double dfHeightInUserUnit = nHeight / dfUserUnit + sMargins.nBottom + sMargins.nTop;

--> nWidth and nHeight are the dimensions of the source raster in pixel.

    if( dfWidthInUserUnit > MAXIMUM_SIZE_IN_UNITS ||
        dfHeightInUserUnit > MAXIMUM_SIZE_IN_UNITS )
    {
        if( pszDPI == NULL )
        {
            if( sMargins.nLeft + sMargins.nRight >= MAXIMUM_SIZE_IN_UNITS ||
                sMargins.nBottom + sMargins.nTop >= MAXIMUM_SIZE_IN_UNITS )
            {
                CPLError(CE_Warning, CPLE_AppDefined,
                         "Margins too big compared to maximum page dimension (%d) "
                         "in user units allowed by Acrobat",
                         MAXIMUM_SIZE_IN_UNITS);
            }
            else
            {
                if( dfWidthInUserUnit >= dfHeightInUserUnit )
                {
                    dfDPI = (int)(0.5 + (double)nWidth / (MAXIMUM_SIZE_IN_UNITS -
                            (sMargins.nLeft + sMargins.nRight)) / USER_UNIT_IN_INCH);
                }
                else
                {
                    dfDPI = (int)(0.5 + (double)nHeight / (MAXIMUM_SIZE_IN_UNITS -
                            (sMargins.nBottom + sMargins.nTop)) / USER_UNIT_IN_INCH);
                }
                CPLDebug("PDF", "Adjusting DPI to %d so that page dimension in "
                        "user units remain in what is accepted by Acrobat", (int)dfDPI);
            }
        }
        else
        {
            CPLError(CE_Warning, CPLE_AppDefined,
                     "The page dimension in user units is %d x %d whereas the "
                     "maximum allowed by Acrobat is %d x %d",
                     (int)(dfWidthInUserUnit + 0.5),
                     (int)(dfHeightInUserUnit + 0.5),
                     MAXIMUM_SIZE_IN_UNITS, MAXIMUM_SIZE_IN_UNITS);
        }
    }


> 
> > Even

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