[PATCH] Enhancement request : specify Tiff Deflate compression level

[quickstuff@…]

Creation of Deflate-compressed TIFF datasets lack a creation-option allowing to
specify the desired compression level.
(so-called zlevel 0-9 in zlib / pseudo-tag TIFFTAG_ZIPQUALITY in libtiff)

[Even Rouault]

Patch provided adding this feature. The only point I'm unsure is the name of the creation-option. I've chosen 'ZLEVEL'. I find ZIPQUALITY a bit confusing (it's a lossless compression).

[warmerdam]

Even,

This patch looks great, go ahead and apply it in trunk.

[Even Rouault]

Commited in trunk in r12575

[quickstuff]

Though the enhancement worked under FWTools 1.4.x, the option ZLEVEL appears to do nothing with subsequent versions (FWTools 2.0.x) based on GDAL 1.5 betas.

Tested with FWTools 2.0.3 Win32:

gdal_translate -of GTiff -co COMPRESS=DEFLATE -co ZLEVEL=9 source.tif dest.tif

Whatever the number used (1...9) the destination file always has exactly the same size/compression ratio.

[warmerdam]

Even,

In our discussion in IRC was I was mixed up about tiffcp. The argument for zip compression is predictor. In fact, I think your earlier analysis is correct and that this isn't a libtiff problem. The difference (I think) was the gutting of GTiffCreateCopy() and change to close, reopen and then use GDALDatasetCopyWholeRaster(). So the change in behavior wasn't (I think) in libtiff, but in geotiff.cpp. Setting the zipquality after the reopen would appear to be the right solution.

I've leave it in your hands.

[Even Rouault]

Fix commited in r13326. I've also fixed JPEG_QUALITY that has the same behaviour.