+----------------------------------------------------------------------+ | tiff2png - converts a Tagged Image File Format (TIFF) file into | | a Portable Network Graphics (PNG) file | | | | Copyright 1996,2000 Willem van Schaik, Singapore (willem@schaik.com) | | Copyright 1999-2002 Greg Roelofs (newt@pobox.com) | | | +----------------------------------------------------------------------+ This is the first attempt for a tiff2png program. Reason to develop it was the lack of conversion possibilities for TIFF files containing alpha channels. Especially NeXT users create lots of TIFF files that have the rather exceptional 2-bit gray and 4-bit color formats, where both can have an alpha channel besides the graphics info. Because PBMplus is not supporting alpha, that path "tifftopnm <file> | pnmtopng > <file>" makes that the alpha and transparency gets lost. I have chosen to use PNG formats as similar as possible to the format of the original TIFF file. Thus, paletted TIFF files will be converted into PNG files with color-type 3 (= paletted). Only for some cased the bit-depth had to be altered to accommodate both standards. At this moment the program supports grayscale images, full-color RGB images, and colormapped (palette) images. This is all in 1 to 16 bits per sample (i.e., up to 64-bit RGBA). The compression is as good as or better than libtiff is, which is pretty OK. I also implemented support for both single-image-planes as well as separated-color-planes. Support for so-called tiled images I have left out, for the time being. [partial support for tiled images added as of version 0.9] Major headaches were the PhotometricInterpretation parameters "min-is-white" and "min-is-black". I couldn't yet figure it out for 100%, but I suspect incompatibilities between older (netpbm) version 2.4 of libtiff and the later v3.x. The "-invert" option is available in case there are still problems with some images. The major decoding and coding work is done by the libtiff, libpng, and zlib libraries; newer versions of libtiff can optionally use libjpeg, as well. So you need to get those as well. The latest versions of libtiff can be found here: http://www.libtiff.org/ Older versions may still exist here: ftp://ftp.sgi.com/graphics/tiff/tiff-v3.4-tar.gz ftp://ftp.x.org/R5contrib/netpbm-1mar1994.tar.gz [contains 2.4] libpng and zlib may be found at these sites: http://www.libpng.org/pub/png/libpng.html http://www.zlib.org/ or here: ftp://swrinde.nde.swri.edu/pub/png/src/ (libpng* or lpng*, and zlib*) libjpeg is available here: http://www.ijg.org/ ftp://ftp.uu.net/graphics/jpeg/ To build, first make zlib, libpng, libjpeg, and libtiff according to their build instructions. Then edit the tiff2png makefile so that the locations of the libraries are correct, and type "make". A separate archive, tiff2png-images.zip, contains some test files; the included script Alpha.sh will convert all of the TIFFs, overwriting the PNGs at the same time. :-) If you have a web browser with adequate alpha support (see http://www.libpng.org/pub/png/pngapbr.html for info and links), you can test the results by loading Alpha.html in your browser and see what happens when you change the background color of the page. I also tested this utility against the test pictures at ftp.sgi.com. With the exception of the tiled images (not retested since support for tiled images was added in tiff2png 0.9), the results were good. But there can and will still be many TIFF files that don't convert correctly. Please send Greg a copy if you come across such a beast--as long as it's not multi-megabytes in size! For the time being I concentrated on straightforward support of as many formats as possible. Future plans are to create PNG chunks for all those informational fields that TIFF also contains, like Name, Date, Position, Resolution, etc. A somewhat bolder plan is to convert the ColorResponseCurves field into PNG gamma/chromaticity or iCCP chunks. We'll see. At the moment there is a command-line parameter to add a gamma chunk to your PNG file; if you know what color space the image pixels are in (e.g., sRGB -> gamma 1/2.2 = 0.45455), you can (and should!) add this information to the PNG file(s). The tiff2png web page is here: http://www.libpng.org/pub/png/apps/tiff2png.html Willem's home page is here: http://www.schaik.com/ Please send bug reports to Greg Roelofs (newt@pobox.com) and thanks to Willem (willem@schaik.com). Greg Roelofs newt@pobox.com
