2007.07.27 07:13 "[Tiff] Scanline-Interface", by Oliver Geisen
Thread
2007.07.27 07:13 "[Tiff] Scanline-Interface", by Oliver Geisen
Hello,
as far as i know the function
int TIFFReadScanline(TIFF *tif, tdata_t buf, uint32 row, tsample_t
sample)
can only handle subsequent lines (no random access).
If find this irritating because the the function name and the 'row'
param suggest that there may be an random access.
int TIFFReadNextScanline(TIFF *tif, tdata_t buf, tsample_t sample) would be more intuitive?!
What will happen if:
- the TIFF is compressed and has only 1 strip of large data? Will libtiff read the whole strip into memory to access the lines?
- one give a non-sequential line number as row-param?
Maybe:
- TIFFReadScanline could random access lines, even if data is compressed using this algo:
strip = (row / rps); // leads in 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
_____________________________
Kreisboten Verlag Mühlfellner KG
82362 Weilheim i. Ob.
Tel. 0881/686-904
Fax 0881/686-74
Sitz Weilheim, AG München, HRA 64016, p.h.G.:
Kreisboten-Verlag Verwaltungsgesellschaft mbH,
Weilheim, AG München, HRB 119773,
Geschäftsführer: Dr. Dirk Ippen, Dr. Gerd Waldenmaier