Q:
I'm working on a screen grab function which clips an image from a
displayed PDF. The idea is that the user can zoom in/out or scroll up/
down on the pdf display and clip an image. The image is then inserted
in an html page.
The attached code (query.cpp) clips the correct region with a
particular zoom factor assuming that the user has not scrolled
horizontally or vertically. (I haven't handled the user scrolling).
The problem is that I can't seem to set the correct horizontal or
vertical scroll position. (At the minute the work around is to simply
add/subtract the horizontal/vertical position of the scroll bars in
pixels. This means that the clip region is not quite correct).
Is there something I'm missing?
1. Should I be able to set the scroll values and then call
pdfview.ConvScreenPtToPagePt? Or do I need to work out the Rect of
the clip region after scrolling by adding/subtracting the scroll
distance to the clip coordinates? If I need to compute/find the clip
region how do I convert the HScrollPos (in canvas pts?) to page pts?
2. Also should I be passing in and setting the page presentation mode
& page view mode in order to clip the correct region. (ie. would these
settings affect the clip region)??
Any advice or suggestions are much appreciated.
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A:
It seems that functionality you would like to implement is very
similar to 'Rectangular Zoom' sample code in #C PDFView sample (part
of PDFNet SDK 3.6; see http://www.pdftron.com/net/samplecode/MyPDFView.cs).
Make sure that you are using the latest version of the SDK because
there were small changes in the way pdfview.SetZoom() works
(previously the zoom point was in the top/right corner, whereas
starting with v.3.6 the zoom point is in the center of the view).
You don't need to scroll the view or to manually adjust H/VScrollPos
because all of this is automatically done in PDFView class. You also
don't need to worry about the page presentation mode & page view mode
because this should work in any mode. So you can obtain H/VScrollPos
values from PDFView class and pass them unchanged to SetScrollsPos();