Readme PTConvert


PTConvert converts Image file formats
and is invoked on the commandline using the
command:

PTConvert Inputfile [-o Outputfile] [-g gamma] [-e oecf] [-q quality] [-s scale]

File formats for input and output are derived from 
file extensions. The following extensions are recognized:

tif, png, jpg 
fjpg - floating point JPEG
img,hdr,pic  - Radiance format. Linear luminance range 0...1 is mapped
       to screen luminance 0..1. This may appear too dark or too bright
       in some other programs (e.g. HDRShop) but can be easily adjusted 
       by setting exposure appropriately.
flt  - private Raw floating point format (huge!)

Options are

Outputfile - Name of Outputfile, defaults to PTConvert_out.tif
gamma      - Gamma value for transforming linear floating point
             data (flt,img,fjpg) into integer data (tif, png, jpg)
             or vice versa. This is not to be confused with the
             gamma correction for electronic displays but models the
             opto electronic conversion function of the image capturing
             device (camera, scanner etc). Defaults to 1. 
oecf       - Text file describing the optoelectronic conversion function. 
             This is a lookup table listing linear luminance for all 256
             byte values. See the example file oecf.txt for details
             of the format. Use only if you happen to know the data for
             your camera.
quality    - Quality of JPEG-compression (0..100) for formats "jpg" and "fjpg".
             Samplesize for formats tif/png; quality < 100 : 8bits,
             quality==100 : 16bits. Default: 80.
scale      - Image data are linearly scaled (brightened/darkened) by this factor.


gamma and oecf may not be used both at the same time. 

PTConvert creates large temporary files. When interrupted or
exiting unnormally PTConvert may not remove all temporary
files and you have to clean up yourself. Temp files have names like
s3vvojk7.3 and reside in the c:\ directory.

Changes in version 0.2

JPEG compression for "fjpg" images is set to "RGB" format. The
reason is as follows:
The JPEG default is YCbCr. The Cb and Cr components are downsampled
by a factor 2:1 and later upsampled during decompression. This
upsampling is handled differently by different programs.
Photoshop simply duplicates pixels, which is the most reasonable
method leading to few artefacts. The standard JPEG-library and
the JAVA-API perform "fancy upsampling" by averaging three
pixels using a triangle filter. This causes visible artefacts
which are amplified by the fjpeg-format. The RGB-format uses 
no downsampling and avoids this problem. However, file size
increases somewhat.
PTConvert uses the standard YCbCr-format for JPEG-output.
             


H. Dersch
der@fh-furtwangen.de




Copyright (c) 2004 H. Dersch

This software uses the following resources:
tifflib
Copyright (c) 1988-1997 Sam Leffler
Copyright (c) 1991-1997 Silicon Graphics, Inc.
jpeglib
Copyright (C) 1995, Thomas G. Lane.
pnglib
Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
zlib
Copyright (C) 1995-1996 Jean-loup Gailly and Mark Adler
rgbE-reader/writer derived from sources published by
Bruce Walter  (bjw@graphics.cornell.edu)


THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 
EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  

IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 
LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
OF THIS SOFTWARE.