1Pamlookup User Manual(0)                              Pamlookup User Manual(0)
2
3
4

NAME

6       pamlookup  -  map an image to a new image by using it as indices into a
7       table
8
9

SYNOPSIS

11       pamlookup -lookupfile=lookupfile [-byplane] -missingcolor=color  [-fit]
12       indexfile
13
14       All  options  can  be abbreviated to their shortest unique prefix.  You
15       may use two hyphens instead of one.  You may separate  an  option  name
16       and its value with white space instead of an equals sign.
17
18

DESCRIPTION

20       This program is part of Netpbm(1).
21
22       pamlookup  takes  a two dimensional array of indices and a lookup table
23       as input.  For each position in the index array, it looks up the  index
24       in  the  lookup table and places the result of the lookup in the output
25       image.
26
27       There are two ways of indexing the lookup table:  whole  tuple  and  by
28       plane.  The -byplane option controls which pamlookup does.
29
30       In  the  simplest form of whole tuple indexing, each index in the index
31       array is a single whole number and the lookup table associates a  whole
32       tuple with each possible whole number index.  So for example, the index
33       array might have at Row 2, Column 9 the value  23.   The  lookup  table
34       might associate the tuple (1,2,3) with the value 23.  In that case, the
35       output image contains the tuple (1,2,3) at Row 2, Column 9.
36
37       In a more complex form of whole tuple indexing, each index in the index
38       array  is  an  ordered pair of whole numbers and the lookup table asso‐
39       ciates a whole tuple with each possible ordered pair index.   Modifying
40       the example above, the index value could be (23, 5) instead of 23.
41
42       With  whole  tuple  indexing,  the  output  thus has the same width and
43       height as the index image, and tuple depth and type and  maxval  deter‐
44       mined by the lookup table.
45
46       With  whole  tuple indexing, if the index image has depth 1, its sample
47       values are single whole number indices.  If the index image  has  depth
48       greater  than  1,  its  tuples are ordered pair indices composed of the
49       first and second sample in the tuple.
50
51       In by plane indexing, the index image contains  whole  number  indices.
52       The  first  sample  of each tuple in the index image is the index.  The
53       lookup table maps each whole number  index  to  another  whole  number.
54       pamlookup looks up each sample from the index image in the lookup table
55       and uses the resulting whole number as the sample value  for  the  same
56       row, column, and plane in the output.
57
58       With  by plane indexing, the output thus has the same dimensions as the
59       index image an the same maxval as the lookup image.
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61
62
63   The Lookup Table Image
64       The lookup table is a PAM or PNM image.  If the  index  image  contains
65       whole number indices, the lookup image is a single row and the index is
66       a column number.  The lookup result is the value of the tuple or  pixel
67       at the indicated column in the one row in the lookup table.  If the in‐
68       dex image contains ordered pair indices, the first element of  the  or‐
69       dered  pair  is a row number and the second element of the ordered pair
70       is a column number.  The lookup result is the value  of  the  tuple  or
71       pixel at the indicated row and column in the lookup table.
72
73       The  width of the lookup image should normally be the maxval of the in‐
74       dex image plus one, so that each possible  index  sample  value  corre‐
75       sponds  to one entry in the lookup table.  There are two ways pamlookup
76       deals with a lookup image that does not have such a width:
77
78
79
80       •      Scale the lookup image to the required width.  pamlookup  always
81              does this with by plane indexing, and with whole tuple indexing,
82              does it when you specify -fit.
83
84
85       •      Use a default value for indices that exceed  the  width  of  the
86              lookup  image  and ignore lookup image columns beyond the maxval
87              of the index image.  pamlookup does this with whole tuple index‐
88              ing when you don't specify -fit.
89
90              You  specify  the  default value with a -missingcolor option; it
91              defaults to the value from the top left corner of the lookup im‐
92              age.
93
94
95       With  ordered  pair  indexes  (which implies whole tuple indexing), the
96       same rule applies to the height of the index image as to the width.
97
98       The mandatory -lookupfile option identifies  the  file  containing  the
99       lookup table image.  - means Standard Input.  It won't work if both the
100       index image file and lookup table file are Standard Input.
101
102       You can use ppmmake and pnmcat to create a lookup table file.
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104
105
106   Example - Whole Tuple Indexing
107       Here is an example of pamlookup's function with  whole  tuple  indexing
108       (-byplane not specified).
109
110       Consider an index image consisting of a 3x2x1 PAM as follows:
111
112
113       0   1   0
114       2   2   2
115
116       and a lookup table consisting of a 3x1 PPM image as follows:
117
118
119       red   yellow   beige
120
121       The lookup table above says Index 0 corresponds to the color red, Index
122       1 corresponds to yellow, and Index 2 corresponds to beige.  The  output
123       of pamlookup is the following PPM image:
124
125
126       red     yellow   red
127       beige   beige    beige
128
129       Now let's look at an example of the more complex case where the indices
130       are ordered pairs of whole numbers instead of whole numbers.  Our index
131       image will be this 3x2x2 PAM image:
132
133
134       (0,0)   (0,1)   (0,0)
135       (1,1)   (1,0)   (0,0)
136
137       Our lookup table for the example will be this two dimensional PPM:
138
139
140       red     yellow   red
141       black   green    red
142
143
144
145   Example - By Plane Indexing
146       Here is an example of pamlookup's function with by plane tuple indexing
147       (-byplane specified).
148
149       Consider an index image consisting of a 3x2x3 PAM as follows:
150
151
152       (0,0,0)   (1,0,0)   (2,0,0)
153       (2,2,0)   (2,0,2)   (2,0,0)
154
155       and a lookup table consisting of a 3x1x1 PAM image  with  maxval  7  as
156       follows:
157
158
159       3   4   7
160
161       The  lookup table above says Index 0 corresponds to the sample value 3,
162       Index 1 corresponds to 4, and Index 2 corresponds to 7.  The output  of
163       pamlookup is the following 3x2x3 PAM image:
164
165
166       (3,3,3)   (4,3,3)   (7,3,3)
167       (7,7,3)   (7,3,7)   (7,3,3)
168
169
170
171   Miscellaneous
172       The  indexfile argument identifies the file containing the index PAM or
173       PNM image.  - means Standard Input.  It won't work if  both  the  index
174       image file and lookup table file are Standard Input.
175
176       The output image goes to Standard Output.
177
178       If you want to use two separate 1-plane images as indices (so that your
179       output reflects the combination of both inputs), use pamstack  to  com‐
180       bine  the  two into one two-plane image (and use a 2-dimensional lookup
181       table image).
182
183
184

OPTIONS

186       In addition to the options common to all programs  based  on  libnetpbm
187       (most notably -quiet, see
188        Common  Options ⟨index.html#commonoptions⟩ ), pamlookup recognizes the
189       following command line options:
190
191
192
193       -lookupfile=lookupfile
194              lookupfile names the file that contains the  PAM  or  PNM  image
195              that is the lookup table.  This option is mandatory.
196
197
198       -byplane
199              This  options  selects  by plane indexing.  The default is whole
200              tuple indexing.
201
202              This option was new in Netpbm 10.72  (September  2015).   Before
203              that, there is no by plane indexing.
204
205
206       -missingcolor=color
207              This  option  is meaningful only if the lookup image (and there‐
208              fore the output) is a PNM image.  color specifies the color that
209              is  to go in the output wherever the index from the input is not
210              present in the lookup table (not present means the index exceeds
211              the  dimensions of the lookup image -- e.g. index is 100 but the
212              lookup image is a 50 x 1 PPM).
213
214              If you don't specify this option or  -fit,  pamlookup  uses  the
215              value  from  the top left corner of the lookup image whenever an
216              index exceeds the dimensions of the lookup image.
217
218              Specify the color (color) as described for the argument  of  the
219              pnm_parsecolor()                 library                 routine
220              ⟨libnetpbm_image.html#colorname⟩ .
221
222              Another way to deal with a too-small lookup image is to use  the
223              -fit option.
224
225              This option has no effect if you also specify -fit or -byplane.
226
227
228       -fit   This  option says to shrink or expand the lookup image as neces‐
229              sary to fit the indices present in the index image, per the  in‐
230              dex image's maxval.  For example, if your index image has a sin‐
231              gle plane and a maxval of 255 and your lookup image is 1 row  of
232              10 columns, pamlookup stretches your lookup image to 255 columns
233              before doing the lookups.  pamlookup  does  the  stretching  (or
234              shrinking) with the pamscale(1) program.
235
236              When you use -fit, pamlookup never fails or warns you because of
237              invalid lookup image dimensions, and  the  -missingcolor  option
238              has no effect.
239
240              -fit  has no effect when you specify -byplane.  pamlookup always
241              has the behavior requested by -fit when it does by plane  index‐
242              ing.
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246

EXAMPLES

248   Example: rainfall map
249       Say  you  have a set of rainfall data in a single plane PAM image.  The
250       rows and columns of the PAM indicate latitude and longitude.  The  sam‐
251       ple values are the annual rainfall in (whole) centimeters.  The highest
252       rainfall value in the image is 199 centimeters.  The image  is  in  the
253       file rainfall.pam.
254
255       You  want  to  produce  a  PPM  rainfall map with green for the wettest
256       places, red for the driest, and other colors in between.
257
258       First, compose a lookup table image, probably with a  graphical  editor
259       and the image blown way up so you can work with individual pixels.  The
260       image must have a single row and 200 columns.  Make the leftmost  pixel
261       red  and the rightmost pixel green and choose appropriate colors in be‐
262       tween.  Call it colorkey.ppm.
263
264           pamlookup rainfall.pam -lookupfile=colorkey.ppm >rainfallmap.ppm
265
266
267       Now lets say you're too lazy to type in 200 color values and nobody re‐
268       ally  cares  about the places that have more than 99 centimeters of an‐
269       nual rainfall.  In that case, just make colorkey.ppm 100  columns  wide
270       and do this:
271
272           pamlookup rainfall.ppm -lookupfile=colorkey.ppm -missingcolor=black \
273              >rainfallmap.ppm
274
275
276       Now  if there are areas that get more than 100 centimeters of rainfall,
277       they will just show up black in the output.
278
279
280   Example: graphical diff
281       Say you want to compare two PBM  (black  and  white)  images  visually.
282       Each  consists  of  black foreground pixels on a white background.  You
283       want to create an image that contains background where both images con‐
284       tain  background  and  foreground where both images contain foreground.
285       But where Image 1 has a foreground pixel and Image 2 does not, you want
286       red  in  the  output;  where Image 2 has a foreground pixel and Image 1
287       does not, you want green.
288
289       First, we create a single image that contains the information from both
290       input PBMs:
291
292           pamstack image1.pbm image2.pbm >bothimages.pam
293
294
295       Note that this image has 1 of 4 possible tuple values at each location:
296       (0,0), (0,1), (1,0), or (1,1).
297
298       Now, we create a lookup table that we can index with those 4 values:
299
300           ppmmake white 1 1 >white.ppm
301           ppmmake black 1 1 >black.ppm
302           ppmmake red   1 1 >red.ppm
303           ppmmake green 1 1 >green.ppm
304           pnmcat -leftright black.ppm red.ppm   >blackred.ppm
305           pnmcat -leftright green.ppm white.ppm >greenwhite.ppm
306           pnmcat -topbottom blackred.ppm greenwhite.ppm >lookup.ppm
307
308
309       Finally, we look up the indices from our index in our lookup table  and
310       produce the output:
311
312           pamlookup bothimages.ppm -lookupfile=lookup.ppm >imagediff.ppm
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316

SEE ALSO

318       pamunlookup(1),   pnmremap(1),   ppmmake(1),   pnmcat(1),  pamstack(1),
319       pnm(1), pam(1)
320
321
322

HISTORY

324       pamlookup was new in Netpbm 10.13 (December 2002).
325

DOCUMENT SOURCE

327       This manual page was generated by the Netpbm tool 'makeman'  from  HTML
328       source.  The master documentation is at
329
330              http://netpbm.sourceforge.net/doc/pamlookup.html
331
332netpbm documentation             25 July 2015         Pamlookup User Manual(0)
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