From 9491825ddff7a294d1f49061bae7044e426aeb2e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Frings-F=C3=BCrst?= Date: Fri, 6 Nov 2015 05:38:49 +0100 Subject: Imported Upstream version 1.8.3 --- tiff/contrib/pds/README | 90 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100755 tiff/contrib/pds/README (limited to 'tiff/contrib/pds/README') diff --git a/tiff/contrib/pds/README b/tiff/contrib/pds/README new file mode 100755 index 0000000..b9abc6b --- /dev/null +++ b/tiff/contrib/pds/README @@ -0,0 +1,90 @@ +Date: Fri, 01 Aug 1997 20:14:52 MDT +To: Sam Leffler + +From: "Conrad J. Poelman (WSAT)" +Subject: Potential TIFF library additions + +Delivery-Date: Fri, 01 Aug 1997 19:21:06 -0700 + +Sam, + +You probably don't remember me, but I sent in a couple of bug fixes +regarding the TIFF library about a 16 months ago or so... + +I just wanted to send you two other additions that I have made to our +local version of the TIFF library in hopes that you will want to +incorporate them into your next major release of the TIFF library. +(These additions are based on TIFF version 3.4beta31, but they sit on +top of the library so they shouldn't be much trouble to incorporate them +into any more recent version.) They are internally documented to a +reasonable extent and we've been successfully using them in our code +here for over a year. If you think they would make good additions to the +TIFF library, I'd be happy to clean them up more, document them more, +and/or integrate them with the latest version of the TIFF library, but I +figured I'd see if you were interested in using them before I went to +all that trouble. + +TIFF Image Iterator +------------------- +Your ReadRGBA() routine works well for reading many different formats +(TILED, STIP, compressed or not, etc.) of the most basic types of data +(RGB, 8-bit greyscale, 8-bit colormapped) into an SGI-style data array, +and serves as a good template for users with other needs. I used it as +an exmaple of how to make an iterator which, rather than fill a data +array, calls an arbitrary user-supplied callback function for each +"chunk" of data - that "chunk" might be a strip or a tile, and might +have one sample-per-pixel or two, and might be 8-bit data or 16-bit or +24-bit. The callback function can do whatever it wants with the data - +store it in a big array, convert it to RGBA, or draw it directly to the +screen. I was able to use this iterator to read 16-bit greyscale and 32- +and 64-bit floating point data, which wasn't possible with ReadRGBA(). + +I have tested this routine with 8- and 16-bit greyscale data as well as +with 32- and 64-bit floating point data. I believe nearly all of our +data is organized in strips, so actually I'd appreciate it if you had +some tiled images that I could test it with. + +It should certainly be possible and would be cleanest to reimplement +ReadRGBA() in terms of the image iterator, but I haven't done that. + + +Private Sub-Directory Read/Write +-------------------------------- +TIFF-PL is a Phillips Laboratory extension to the TIFF tags that allows +us to store satellite imaging-specific information in a TIFF format, +such as the satellite's trajectory, the imaging time, etc. In order to +give us the flexibility to modify the tag definitions without getting +approval from the TIFF committee every time, we were given only three +TIFF tags - a PL signature, a PL version number, and PL directory +offset, which lists the position in the file at which to find a private +sub-directory of tags-value pairs. So I wrote two routines: +TIFFWritePrivateDataSubDirectory(), which takes a list of tags and a +"get" function and writes the tag values into the TIFF file, returning +the offset within the file at which it wrote the directory; and +TIFFReadPrivateDataSubDirectory(), which takes an offset, a list of +tags, and a "set" function and reads all the data from the private +directory. The functions themselves are pretty simple. (The files are +huge because I had to basically copy all of the tif_dirread.c and +tif_dirwrite.c files in order to access the various fetching routines +which were all declared static and therefore inaccessible in the TIFF +library.) + + +I'm including the four source files (tif_imgiter.h, tif_imgiter.c, +tif_pdsdirread.c, tif_pdsdirwrite.c) in case you want to take a look at +them. I can also send you some sample code that uses them if you like. +If you're interested in having them incorporated into the standard TIFF +library, I'd be happy to do that integration and clean up and document +the routines. (For example, I've already realized that instead of +limiting the SEP callback function to three bands (R,G,B) it should take +an array to enable the handling of n-banded multi-spectral data...) If +not, I'll just leave them as they are, since they work fine for us now. + +Holler if you have any questions. + +-- Conrad +__________________________________________________________________ + Capt Conrad J. Poelman PL/WSAT (Phillips Laboratory) + 505-846-4347 3550 Aberdeen Ave SE + (FAX) 505-846-4374 Kirtland AFB, NM 87117-5776 + -- cgit v1.2.3