- A single hyphen instead of an input file name will cause pbmtojbg to read the data from
standard input instead from a file.
-q Encode the image in one single resolution layer (sequential mode). This is usually the most
efficient compression method. By default, the number of resolution layers is chosen
automatically such that the lowest layer image is not larger than 640 × 480 pixels. This is
a shortcut for -d0.
-xnumber Specify the maximal horizontal size of the lowest resolution layer. The default is 640
pixels.
-ynumber Specify the maximal vertical size of the lowest resolution layer. The default is 480
pixels.
-lnumber Select the lowest resolution layer that will be written to the BIE. It is possible to store
the various resolution layers of a JBIG1 image in progressive mode into different BIEs.
Options -l and -h allow to select the resolution-layer interval that will appear in the
created BIE. The lowest resolution layer has number 0 and this is also the default value.
By default all layers will be written.
-hnumber Select the highest resolution layer that will be written to the BIE. By default all layers
will be written. See also option -l.
-b Use binary values instead of Gray code words in order to encode pixel values in multiple
bitplanes. This option has only an effect if the input is a PGM file and if more than one
bitplane is produced. Note that the decoder has to make the same selection but cannot
determine from the BIE, whether Gray or binary code words were used by the encoder.
-dnumber Specify the total number of differential resolution layers into which the input image will
be split in addition to the lowest layer. Each additional layer reduces the size of layer 0
by 50 %. This option overrides options -x and -y which are usually a more comfortable way
of selecting the number of resolution layers.
-snumber The JBIG1 algorithm splits each image into a number of horizontal stripes. This option
specifies that each stripe shall have number lines in layer 0. The default value is
selected so that approximately 35 stripes will be used for the whole image.
-mnumber Select the maximum horizontal offset of the adaptive template pixel. The JBIG1 encoder
uses ten neighbour pixels to estimate the probability of the next pixel being black or
white. It can move one out of these ten pixels. This is especially useful for dithered
images, as long as the distance of this adaptive pixel can be adjusted to the period of the
dither pattern. By default, the adaptive template pixel is allowed to move up to 8 pixels
away horizontally. This encoder supports distances up to 127 pixels. Annex A of the
standard suggests that decoders should support at least a horizontal distance of 16 pixels,
so using values not higher than 16 for number might increase the chances of
interoperability with other JBIG1 implementations. On the other hand, the T.85 fax
application profile requires decoders to support horizontal offsets up to 127 pixels, which
the maximum value permitted by the standard. (The maximal vertical offset of the adaptive
template pixel is always zero for this encoder.)
-tnumber Encode only the specified number of most significant bit planes. This option allows one to
reduce the depth of an input PGM file if not all bits per pixel are needed in the output.
-onumberJBIG1 separates an image into several horizontal stripes, resolution layers and planes,
were each plane contains one bit per pixel. One single stripe in one plane and layer is
encoded as a data unit called stripe data entity (SDE) inside the BIE. There are 12
different possible orders in which the SDEs can be stored inside the BIE and number selects
which one shall be used. The order of the SDEs is only relevant for applications that want
to decode a JBIG1 file which has not yet completely arrived from e.g. a slow network
connection. For instance some applications prefer that the outermost of the three loops
(stripes, layers, planes) is over all layers so that all data of the lowest resolution
layer is transmitted first.
The following values for number select these loop arrangements for writing the SDEs
(outermost loop first):
0 planes, layers, stripes
2 layers, planes, stripes
3 layers, stripes, planes
4 stripes, planes, layers
5 planes, stripes, layers
6 stripes, layers, planes
All loops count starting with zero, however by adding 8 to the above order code, the layer
loop can be reversed so that it counts down to zero and then higher resolution layers will
be stored before lower layers. Default order is 3 which writes at first all planes of the
first stripe and then completes layer 0 before continuing with the next layer and so on.
-pnumber This option allows one to activate or deactivate various optional algorithms defined in the
JBIG1 standard. Just add the numbers of the following options which you want to activate in
order to get the number value:
4 deterministic prediction (DPON)
8 layer 0 typical prediction (TPBON)
16 diff. layer typ. pred. (TPDON)
64 layer 0 two-line template (LRLTWO)
Except for special applications (like communication with JBIG1 subset implementations) and
for debugging purposes you will normally not want to change anything here. The default is
28, which provides the best compression result.
-Cstring Add the string in a comment marker segment to the produced data stream. (There is no
support at present for adding comments that contain the zero byte.)
-c Determine the adaptive template pixel movement as suggested in annex C of the standard. By
default the template change takes place directly in the next line, which is most effective.
However, a few conformance test examples in the standard require the adaptive template
change to be delayed until the first line of the next stripe. This option selects this
special behavior, which is normally not required except in order to pass some conformance
tests.
-r Use the SDRST marker instead of the normal SDNORM marker. The probably only useful
application of this option is to generate test data for checking whether a JBIG1 decoder
has implemented SDRST correctly. In a normal JBIG1 data stream, each stripe data entity
(SDE) is terminated by an SDNORM marker, which preserves the state of the arithmetic
encoder (and more) for the next stripe in the same layer. The alternative SDRST marker
resets this state at the end of the stripe.
-Ynumber A long time ago, there were fax machines that couldn't even hold a single page in memory.
They had to start transmitting data before the page was scanned in completely and the
length of the image was known. The authors of the standard added a rather ugly hack to the
otherwise beautiful JBIG1 format to support this. The NEWLEN marker segment can override
the image height stated in the BIE header anywhere later in the data stream. Normally
pbmtojbg never generates NEWLEN marker segments, as it knows the correct image height when
it outputs the header. This option is solely intended for the purpose of generating test
files with NEWLEN marker segments. It can be used to specify a higher initial image height
for use in the BIE header, and pbmtojbg will then add a NEWLEN marker segment at the latest
possible opportunity to the data stream to signal the correct final height.
-f This option makes the output file comply to the "facsimile application profile" defined in
ITU-T Recommendation T.85. It is a shortcut for -q-o0-p8-s128-t1-m127.
-v After the BIE has been created, a few technical details of the created file will be listed
(verbose mode).
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