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August 2007

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2007.08.22 06:19 "Get random lines using TIFFReadScanline()", by Oliver Geisen

Hello,

as far as i know the function can only handle subsequent lines (no  
random access).
The API of this function is not very good, because it implies some  
random access to the programmer by using the 'row' property.
Maybe it would be better this way:
   TIFFReadFirstScanline()
   TIFFReadNextScanline()

Here is a way to provide random access for TIFFReadScanline:

     strip = (row / rps);  // points to the absolute strip (do -1 to  
get an offset)
     stripsize = TIFFStripSize(tiff);
     TIFFReadEncodedStrip(tiff, strip, stripdata, stripsize);
     stripline = (row % rps);  // get the line# inside the strip
     linesize = TIFFScanlineSize(tiff);  // get the size of one line
     offset = (stripline-1) * linesize;  // offset from stripdata to  
begin of line
     return (stripdata + offset);  // return pointer to wanted line


Oliver Geisen
Systemadministrator
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