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January 1997

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1997.01.10 15:55 "TIFFRead/WriteScanline question", by Sven Devriese

Hello all,

the man page for TIFFWriteScanline mentions that
for Planarconfiguration = 1 (PLANARCONFIG_CONTIG)
"the library does not pack the block-interleaved
samples".  I guess this means that the bit planes
are not separated before the data is written to
file.
Similarily, the man page for TIFFReadScanline says:
"The data are returned decompressed and <marshalled>
but are otherwise packed."  It also says at the bottom
that if you want to unpack the block-interleaved
samples (I think that's contiguous pixel data e.g.
RGBRGBRGB, right ?) you have to use the strip- and
tile-based interfaces to read these formats.

If I understand this correctly, I can read/write
compressed scanlines of a plane-separate image
(i.e. pc = 2) but they are compressed differently
than when I read/write scanlines of the equivalent
block-interleaved (i.e. pc = 1) image.

Or does it mean that I just cannot read/write compressed
TIF files using the scanline interface ?

I need to know because, for incorporating libtiff
into our own software, I may only use the scanline
interface for reading/writing pixel data.

I think maybe the terminology is getting to me.
Can anyone clarify this for me ?

Thank you for your time.

Sven.