Tifftopnm User Manual(0) Tifftopnm User Manual(0) NNAAMMEE tifftopnm - convert a TIFF file into a PNM image SSYYNNOOPPSSIISS ttiiffffttooppnnmm [--aallpphhaaoouutt=={_a_l_p_h_a_-_f_i_l_e_n_a_m_e,--}] [--hheeaaddeerrdduummpp] [--vveerrbboossee] [--rreessppeeccttffiilllloorrddeerr] [--bbyyrrooww] [--oorriieennttrraaww] [_t_i_f_f_-_f_i_l_e_n_a_m_e] DDEESSCCRRIIPPTTIIOONN This program is part of NNeettppbbmm(1). ttiiffffttooppnnmm reads a TIFF file as input and produces a PNM image as output. The type of the output file depends on the input file - if it's black and white, ttiiffffttooppnnmm generates a PBM image; if it's grayscale, it generates a PGM image; otherwise, the output is PPM. The program tells you which type it is writing. If the TIFF file contains multiple images (multiple "directories"), ttiiffffttooppnnmm generates a multi-image PNM output stream. Before Netpbm 10.27 (March 2005), however, it would just ignore all but the first input image. The _t_i_f_f_-_f_i_l_e_n_a_m_e argument names the file that contains the Tiff image. If you specify "-" or don't specify this argument, ttiiffffttooppnnmm uses Standard Input. In either case, before Netpbm 10.70 (March 2015), the file must be seekable. That means no pipe, but any regular file is fine. In current Netpbm, the file need not be seekable, but if it isn't, ttiiffffttooppnnmm creates a temporary regular file containing the entire image, so you must have resources for that (and it may defeat your reason for using a pipe). TTIIFFFF CCaappaabbiilliittyy ppaammttoottiiffff uses the Libtiff.org TIFF library (or whatever equivalent you provide) to interpret the TIFF input. So the set of files it is able to interpret is determined mostly by that library. This program cannot read every possible TIFF file -- there are myriad variations of the TIFF format. However, it does understand monochrome and gray scale, RGB, RGBA (red/green/blue with transparency channel), CMYK (Cyan-Magenta-Yellow-Black ink color separation), and color palette TIFF files. An RGB file can have either single plane (interleaved) color or multiple plane format. The program reads 1-8 and 16 bit-per-sample input, the latter in either bigendian or littlendian encoding. Tiff directory information may also be either bigendian or littlendian. There are many TIFF formats that ttiiffffttooppnnmm can read only if the image is small enough to fit in memory. ttiiffffttooppnnmm uses the TIFF library's TIFFRGBAImageGet() function to process the TIFF image if it can get enough memory for TIFFRGBAImageGet() to store the whole image in memory at once (that's what TIFFRGBAImageGet() does). If not, ttiiffffttooppnnmm uses a more primitive row-by-row conversion strategy using the raw data returned by TIFFReadScanLine() and native intelligence. That native intelligence does not know as many formats as TIFFRGBAImageGet() does. And certain compressed formats simply cannot be read with TIFFReadScanLine(). Before Netpbm 10.11 (October 2002), ttiiffffttooppnnmm never used TIFFRGBAImageGet(), so it could not interpret many of the formats it can interpret today. There is no fundamental reason that this program could not read other kinds of TIFF files even when they don't fit in memory all at once. The existing limitations are mainly because no one has asked for more. OOuuttppuutt IImmaaggee The PNM output has the same maxval as the Tiff input, except that if the Tiff input is colormapped (which implies a maxval of 65535) the PNM output has a maxval of 255. Though this may result in lost information, such input images hardly ever actually have more color resolution than a maxval of 255 provides and people often cannot deal with PNM files that have maxval > 255. By contrast, a non-colormapped Tiff image that doesn't need a maxval > 255 doesn't _h_a_v_e a maxval > 255, so when ttiiffffttooppnnmm sees a non-colormapped maxval > 255, it takes it seriously and produces a matching output maxval. Another exception is where the TIFF maxval is greater than 65535, which is the maximum allowed by the Netpbm formats. In that case, ttiiffffttooppnnmm uses a maxval of 65535, and you lose some information in the conversion. OOPPTTIIOONNSS You may abbreviate any option to its shortest unique prefix. You may use two hyphens instead of one in options. You may separate an option and its value either by an equals sign or white space. --aallpphhaaoouutt==_a_l_p_h_a_-_f_i_l_e_n_a_m_e ttiiffffttooppnnmm creates a PGM file containing the alpha channel values in the input image. If the input image doesn't contain a transparency channel, the _a_l_p_h_a_-_f_i_l_e_n_a_m_e file contains all zero (transparent) transparency values. If you don't specify --aallpphhaaoouutt, ttiiffffttooppnnmm does not generate a transparency file, and if the input image has an transparency channel, ttiiffffttooppnnmm simply discards it. If you specify -- as the filename, ttiiffffttooppnnmm writes the transparency output to Standard Output and discards the image. See ppaammccoommpp(1) for one way to use the transparency output file. --rreessppeeccttffiilllloorrddeerr By default, ttiiffffttooppnnmm ignores the "fillorder" tag in the TIFF input, which means it may incorrectly interpret the image. To make it follow the spec, use this option. For a lengthy but engaging discussion of why ttiiffffttooppnnmm works this way and how to use the --rreessppeeccttffiilllloorrddeerr option, see the note on fillorder below. --bbyyrrooww This option can make ttiiffffttooppnnmm run faster. ttiiffffttooppnnmm has two ways to do the conversion from Tiff to PNM, using respectively two facilities of the TIFF library: Whole Image Decode the entire image into memory at once, using TTIIFFFFRRGGBBAAIImmaaggeeGGeett(()), then convert to PNM and output row by row. Row By Row Read, convert, and output one row at a time using TTIIFFFFRReeaaddSSccaannlliinnee(()) Whole Image is preferable because the Tiff library does more of the work, which means it understands more of the Tiff format possibilities now and in the future. Also, some compressed TIFF formats don't allow you to extract an individual row. Row By Row uses far less memory, which means with large images, it can run in environments where Whole Image cannot and may also run faster. And because Netpbm code does more of the work, it's possible that it can be more flexible or at least give better diagnostic information if there's something wrong with the TIFF. The Netpbm native code may do something correctly that the TIFF library does incorrectly, or vice versa. In Netpbm, we stress function over performance, so by default we try Whole Image first, and if we can't get enough memory for the decoded image or TTIIFFFFRRGGBBAAIImmaaggeeGGeett(()) fails, we fall back to Row By Row. But if you specify the --bbyyrrooww option, ttiiffffttooppnnmm will not attempt Whole Image. If Row By Row does not work, it simply fails. See Color Separation (CMYK) TIFFs <#cmyk> for a description of one way Row By Row makes a significant difference in your results. Whole Image costs you precision when your TIFF image uses more than 8 bits per sample. TTIIFFFFRRGGBBAAIImmaaggeeGGeett(()) converts the samples to 8 bits. ttiiffffttooppnnmm then scales them back to maxval 65535, but the lower 8 bits of information is gone. In many versions of the TIFF library, TTIIFFFFRRGGBBAAIImmaaggeeGGeett(()) does not correctly interpret TIFF files in which the raster orientation is column-major (i.e. a row of the raster is a column of the image). With such a TIFF library and file, you must use --bbyyrrooww to get correct output. Before Netpbm 10.11 (October 2002), ttiiffffttooppnnmm always did Row By Row. Netpbm 10.12 always tried Whole Image first. --bbyyrrooww came in with Netpbm 10.13 (January 2003). --oorriieennttrraaww A TIFF stream contains raster data which can be arranged in the stream various ways. Most commonly, it is arranged by rows, with the top row first, and the pixels left to right within each row, but many other orientations are possible. The common orientation is the same one the Netpbm formats use, so ttiiffffttooppnnmm can do its jobs quite efficiently when the TIFF raster is oriented that way. But if the TIFF raster is oriented any other way, it can take a considerable amount of processing for ttiiffffttooppnnmm to convert it to Netpbm format. --oorriieennttrraaww says to produce an output image that represents the raw raster in the TIFF stream rather than the image the TIFF stream is supposed to represent. In the output, the top left corner corresponds to the start of the TIFF raster, the next pixel to the right is the next pixel in the TIFF raster, etc. ttiiffffttooppnnmm can do this easily, but you don't get the right image out. You can use ppaammfflliipp to turn the output into the image the TIFF stream represents (but if you do that, you pretty much lose the benefit of --oorriieennttrraaww). With this option, ttiiffffttooppnnmm always uses the Row By Row method (see --bbyyrrooww). This option was new in Netpbm 10.42 (March 2008). Before that, ttiiffffttooppnnmm generally produces arbitrary results with TIFF images that have an orientation other than the common one. --vveerrbboossee Print extra messages to Standard Error about the conversion. --hheeaaddeerrdduummpp Dump TIFF file information to stderr. This information may be useful in debugging TIFF file conversion problems. NNOOTTEESS FFiilllloorrddeerr There is a piece of information in the header of a TIFF image called "fillorder." The TIFF specification quite clearly states that this value tells the order in which bits are arranged in a byte in the description of the image's pixels. There are two options, assuming that the image has a format where more than one pixel can be represented by a single byte: 1) the byte is filled from most significant bit to least significant bit going left to right in the image; and 2) the opposite. However, there is confusion in the world as to the meaning of fillorder. Evidence shows that some people believe it has to do with byte order when a single value is represented by two bytes. These people cause TIFF images to be created that, while they use a MSB-to-LSB fillorder, have a fillorder tag that says they used LSB-to- MSB. A program that properly interprets a TIFF image will not end up with the image that the author intended in this case. For a long time, ttiiffffttooppnnmm did not understand fillorder itself and assumed the fillorder was MSB-to-LSB regardless of the fillorder tag in the TIFF header. And as far as I know, there is no legitimate reason to use a fillorder other than MSB-to-LSB. So users of ttiiffffttooppnnmm were happily using those TIFF images that had incorrect fillorder tags. So that those users can continue to be happy, ttiiffffttooppnnmm today continues to ignore the fillorder tag unless you tell it not to. (It does, however, warn you when the fillorder tag does not say MSB-to-LSB that the tag is being ignored). If for some reason you have a TIFF image that actually has LSB-to-MSB fillorder, and its fillorder tag correctly indicates that, you must use the --rreessppeeccttffiilllloorrddeerr option on ttiiffffttooppnnmm to get proper results. Examples of incorrect TIFF images are at ftp://weather.noaa.gov. They are apparently created by a program called ffaaxxttoottiiffff. This note was written on January 1, 2002. CCoolloorr SSeeppaarraattiioonn ((CCMMYYKK)) TTIIFFFFss Some TIFF images contain color information in CMYK form, whereas PNM images use RGB. There are various formulas for converting between these two forms, and ttiiffffttooppnnmm can use either of two. The TIFF library (Version 3.5.4 from libtiff.org) uses Y=(1-K)*(1-B) (similar for R and G) in its TIFFRGBAImageGet() service. When ttiiffffttooppnnmm works in Whole Image mode, it uses that service, so that's the conversion you get. But when ttiiffffttooppnnmm runs in Row By Row mode, it does not use TIFFRGBAImageGet(), and you get what appears to be more useful: Y=1-(B+K). This is the inverse of what ppnnmmttoottiiffffccmmyykk does. See the --bbyyrrooww option for more information on Whole Image versus Row By Row mode. Before Netpbm 10.21 (March 2004), ttiiffffttooppnnmm used the Y=(1-K)*(1-B) formula always. SSEEEE AALLSSOO ppnnmmttoottiiffff(1), ppnnmmttoottiiffffccmmyykk(1), ppaammccoommpp(1), ppnnmm(5) AAUUTTHHOORR Derived by Jef Poskanzer from tif2ras.c, which is Copyright (c) 1990 by Sun Microsystems, Inc. Author: Patrick J. Naughton (_n_a_u_g_h_t_o_n_@_w_i_n_d_._s_u_n_._c_o_m). DDOOCCUUMMEENNTT SSOOUURRCCEE This manual page was generated by the Netpbm tool 'makeman' from HTML source. The master documentation is at hhttttpp::////nneettppbbmm..ssoouurrcceeffoorrggee..nneett//ddoocc//ttiiffffttooppnnmm..hhttmmll netpbm documentation 02 January 2015 Tifftopnm User Manual(0)