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unpaper 0.3-1
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------------------------------------------------------------------------------
unpaper 0.3 - written by Jens Gulden 2005-2007
Licensed under the GNU General Public License (GPL), see file LICENSE. 
This software comes with no warranty.
------------------------------------------------------------------------------

Overview
------------------------------------------------------------------------------
unpaper is a post-processing tool for scanned sheets of paper, especially for
book pages that have been scanned from previously created photocopies.
The main purpose is to make scanned book pages better readable on screen
after conversion to PDF. Additionally, unpaper might be useful to enhance
the quality of scanned pages before performing optical character recognition
(OCR).

unpaper tries to clean scanned images by removing dark edges that appeared
through scanning or copying on areas outside the actual page content (e.g.
dark areas between the left-hand-side and the right-hand-side of a double-
sided book-page scan).
The program also tries to detect disaligned centering and rotation of pages
and will automatically straighten each page by rotating it to the correct
angle. This process is called "deskewing".
Note that the automatic processing will sometimes fail. It is always a good
idea to manually control the results of unpaper and adjust the parameter
settings according to the requirements of the input. Each processing step can
also be disabled individually for each sheet.

Input and output files can be in either .pbm , .pgm or .ppm format, thus
generally in .pnm format, as also used by the Linux scanning tools scanimage
and scanadf.
Conversion to PDF can e.g. be achieved with the Linux tools pgm2tiff, tiffcp
and tiff2pdf.

Installation
------------------------------------------------------------------------------
On i386-Linux systems, the pre-compiled binary included in the distribution
archive can be used. Execute as root:

cp bin/unpaper /usr/local/bin/

Alternative ways to install are running 

./make.sh
./make.sh install

Or compile manually and copy the resulting executable to a directory in the
search path.

Compilation
------------------------------------------------------------------------------
The easiest way to manually compile unpaper is running:

gcc -lm -o unpaper unpaper.c

You can also perform this step by invoking the script make. In this case,
optional compilation parameters set via the gobal environment variable $CFLAGS
will also take effect.

unpaper has been tested to be compilable on several hardware platforms and
operating systems, including Linux/Intel, Macintosh/G4, Macintosh/68k,
Solaris/Sparc and Windows/Intel. The following list gives hint on how to
optimally compile unpaper on different systems. This may or may not work
in other environments:

Linux/Intel
The binary executable included in the distribution archive has been compiled
using gcc version 4.1:
gcc -D TIMESTAMP="<yyyy-MM-dd HH:mm:ss>" -lm -O3 -funroll-all-loops -fomit-frame-pointer -ftree-vectorize -o unpaper unpaper.c

Compilation hints for other environments have been provided by users. Note
that the following compiler invocations might work only with specific versions
of the compilers or specific environments:

Macintosh
gcc -O4 -fast -mcpu=7450 -pipe -fomit-frame-pointer -ftree-vectorize -o unpaper unpaper.c
(People with G5  should simply omit the -mcpu=7450 option. Thanks to Olaf Marzocchi.)

In case you use cc as compiler, it may be necessary to increase the stack size
by adding -Wl,-stack_size -Wl,1000000 (tested on Macintosh/68k).

Windows
gcc.exe unpaper.c -o unpaper.exe -I "C:\programme\Dev-Cpp\include" -L "C:\programme\Dev-Cpp\lib" 
(Thanks to Uwe Dierolf.)


Usage
------------------------------------------------------------------------------
Usage: unpaper [options] <input-file(s)> <output-file(s)>

Filenames may contain a formatting placeholder starting with '%' to insert a
page counter for multi-page processing. E.g.: 'scan%03d.pbm' to process files
scan001.pbm, scan002.pbm, scan003.pbm etc.

-l --layout single                   Set default layout options for a sheet:
           |double                   'single': One page per sheet.
           |none                     'double': Two pages per sheet, landscape
                                         orientation (one page on the left
                                         half, one page on the right half).
                                     'none': No auto-layout, mask-scan-points
                                         may individually be specified.
                                     Using 'single' or 'double' automatically
                                     sets corresponding --mask-scan-points.
                                     The default is 'single'.

-start --start-sheet <sheet>         Number of first sheet to process in multi-
                                     sheet mode. (default: 1)

-end --end-sheet <sheet>             Number of last sheet to process in multi-
                                     sheet mode. -1 indicates processing until
                                     no more input file with the corresponding
                                     page number is available (default: -1)

-# --sheet                           Optionally specifies which sheets to
     <sheet>{,<sheet>[-<sheet>]}     process in the range between start-sheet
                                     and end sheet.

-x --exclude                         Excludes sheets from processing in the
     <sheet>{,<sheet>[-<sheet>]}     range between start-sheet and end-sheet.

--pre-rotate -90|90                  Rotates the whole image clockwise (90) or
                                     or anti-clockwise (-90) before any other
                                     processing.

--post-rotate -90|90                 Rotates the whole image clockwise (90) or
                                     or anti-clockwise (-90) after any other
                                     processing.

-M --pre-mirror                      Mirror the image, after possible pre-
     [v[ertical]][,][h[orizontal]]   rotation. Either 'v' (for vertical
                                     mirroring), 'h' (for horizontal mirroring)
                                     or 'v,h' (for both) can be specified.

--post-mirror                        Mirror the image, after any other
  [v[ertical]][,][h[orizontal]]      processing except possible post-
                                     rotation.

--pre-shift <h>,<v>                  Shift the image before further processing.
                                     Values for 'h' (horizontal shift) and 'v'
                                     (vertical shift) can either be positive
                                     or negative.

--post-shift <h>,<v>                 Shift the image after other processing.
                                     Values for 'h' (horizontal shift) and 'v'
                                     (vertical shift) can either be positive
                                     or negative.

--pre-wipe                           Manually wipe out an area before further
  <left>,<top>,<right>,<bottom>      processing. Any pixel in a wiped area
                                     will be set to white. Multiple areas to
                                     be wiped may be specified by multiple
                                     occurrences of this options.

--post-wipe                          Manually wipe out an area after
  <left>,<top>,<right>,<bottom>      processing. Any pixel in a wiped area
                                     will be set to white. Multiple areas to
                                     be wiped may be specified by multiple
                                     occurrences of this options.

--pre-border                         Clear the border-area of the sheet before
  <left>,<top>,<right>,<bottom>      further processing. Any pixel in the
                                     border area will be set to white.

--post-border                        Clear the border-area after processing.
  <left>,<top>,<right>,<bottom>      Any pixel in the border area will be set
                                     to white.

--pre-mask <x1>,<y1>,<x2>,<y2>       Specify masks to apply before any other
                                     processing. Any pixel outside a mask
                                     will be set to white, unless another mask
                                     includes this pixel.
                                     Only pixels inside a mask will remain.
                                     Multiple masks may be specified. No
                                     deskewing will be applied to the masks
                                     specified by --pre-mask.

-s --size <width>,<height>           Change the sheet size before other pro-
          | <size-name>              cessing is applied. Content on the sheet
                                     gets zoomed to fit to the appropriate
                                     size, but the aspect ratio is preserved.
                                     Instead, if the sheet's aspect ratio
                                     changes, the zoomed content gets centered
                                     on the sheet. Size-name can also be a
                                     standard name as 'a4', 'letter', etc.
                                     Possible size names are:
                                     a5
                                     a4
                                     a3
                                     letter
                                     legal.
                                     All size names can also be applied in
                                     rotated landscape orientation, use
                                     'a4-landscape', 'letter-landscape' etc.

--post-size <width>,<height>|<name>  Change the sheet size preserving the
                                     content's aspect ratio after other
                                     processing steps are applied.

--stretch <width>,<height>|<name>    Change the sheet size before other
                                     processing is applied. Content on the
                                     sheet gets stretched to the specified
                                     size, possibly changing the aspect ratio.

--post-stretch <width>,<height>      Change the sheet size after other
               |<name>               processing is applied. Content on the
                                     sheet gets stretched to the specified
                                     size, possibly changing the aspect ratio.

-z --zoom <factor>                   Change the sheet size according to the
                                     given factor before other processing is
                                     done.

--post-zoom <factor>                 Change the sheet size according to the
                                     given factor after processing is done.

-bn --blackfilter-scan-direction     Directions in which to search for solidly
     [v[ertical]][,][h[orizontal]]   black areas. Either 'v' (for vertical
                                     scanning), 'h' (for horizontal scanning)
                                     of 'v,h' (for both) can be specified.
                                     (default: 'v,h')

-bs --blackfilter-scan-size          Width of virtual bar used for mask
      <size>|<h-size>,<v-size>       detection. Two values may be specified
                                     to individually set horizontal and
                                     vertical size. (default: 20,20)

-bd --blackfilter-scan-depth         Size of virtual bar used for black area
      <depth>|<h-depth,v-depth>      detection. (default: 500,500)

-bp --blackfilter-scan-step          Steps to move virtual bar for black area
      <step>|<h-step,v-step>         detection. (default: 5,5)

-bt --blackfilter-scan-threshold <t> Ratio of dark pixels above which a black
                                     area gets detected. (default: 0.95).

-bx --blackfilter-scan-exclude       Area on which the blackfilter should not
      <left>,<top>,<right>,<bottom>  operate. This can be useful to prevent
                                     the blackfilter from working on inner
                                     page content. May be specified multiple
                                     times to set more than one area.

-bi --blackfilter-intensity <i>      Intensity with which to delete black
                                     areas. Larger values will leave less
                                     noise-pixels around former black areas,
                                     but may delete page content. (default:
                                     20)

-ni --noisefilter-intensity <n>      Intensity with which to delete individual
                                     pixels or tiny clusters of pixels. Any
                                     cluster which only contains n dark pixels
                                     together will be deleted. (default: 4)

-ls --blurfilter-size                Size of blurfilter area to search for
      <size>|<h-size>,<v-size>       'lonely' clusters of pixels.
                                     (default: 100,100)

-lp --blurfilter-step                Size of 'blurring' steps in each
      <step>|<h-step>,<v-step>       direction. (default: 50,50)

-li --blurfilter-intensity <ratio>   Relative intensity with which to delete
                                     tiny clusters of pixels. Any blurred area
                                     which contains at most the ratio of dark
                                     pixels will be cleared. (default: 0.01)

-gs --grayfilter-size                Size of grayfilter mask to search for
      <size>|<h-size>,<v-size>       'gray-only' areas of pixels.
                                     (default: 50,50)

-gp --grayfilter-step                Size of steps moving the grayfilter mask
      <step>|<h-step>,<v-step>       in each direction. (default: 20,20)

-gt --grayfilter-threshold <ratio>   Relative intensity of grayness which is
                                     accepted before clearing the grayfilter
                                     mask in cases where no black pixel is
                                     found in the mask. (default: 0.5)

-p --mask-scan-point <x>,<y>         Manually set starting point for mask-
                                     detection. Multiple --mask-scan-point
                                     options may be specified to detect
                                     multiple masks.

-m --mask <x1>,<y1>,<x2>,<y2>        Manually add a mask, in addition to masks
                                     automatically detected around the --mask-
                                     scan-point coordinates (unless --no-mask-
                                     scan is specified).
                                     Any pixel outside a mask will be
                                     set to white, unless another mask
                                     covers this pixel.

-mn --mask-scan-direction            Directions in which to search for mask
     [v[ertical]][,][h[orizontal]]   borders, starting from --mask-scan-point
                                     coordinates. Either 'v' (for vertical
                                     scanning), 'h' (for horizontal scanning)
                                     of 'v,h' (for both) can be specified.
                                     (default: 'h' ('v' may cut text-
                                     paragraphs on single-page sheets))

-ms --mask-scan-size <size>|<h,v>    Width of the virtual bar used for mask
                                     detection. Two values may be specified
                                     to individually set horizontal and
                                     vertical size. (default: 50,50)

-md --mask-scan-depth <dep>|<h,v>    Height of the virtual bar used for mask
                                     detection. (default: -1,-1, using the
                                     total width or height of the sheet)

-mp --mask-scan-step <step>|<h,v>    Steps to move the virtual bar for mask
                                     detection. (default: 5,5)

-mt --mask-scan-threshold <t>|<h,v>  Ratio of dark pixels below which an edge
                                     gets detected, relative to max. blackness
                                     when counting from the start coordinate
                                     heading towards one edge. (default: 0.1)

-mm --mask-scan-minimum <w>,<h>       Minimum allowed size of an auto-detected
                                     mask. Masks detected below this size will
                                     be ignored and set to the size specified
                                     by mask-scan-maximum. (default: 100,100)

-mM --mask-scan-maximum <w>,<h>       Maximum allowed size of an auto-detected
                                     mask. Masks detected above this size will
                                     be shrunk to the maximum value, each
                                     direction individually. (default:
                                     sheet size, or page size derived from
                                     --layout option.

-mc --mask-color <color>             Color value with which to wipe out pixels
                                     not covered by any mask. Maybe useful for
                                     testing in order to visualize the effect
                                     of masking. (Note that an RGB-value is
                                     expected: R*65536 + G*256 + B.)

-dn --deskew-scan-direction          Edges from which to scan for rotation.
     [left],[top],[right],[bottom]   Each edge of a mask can be used to detect
                                     the mask's rotation. If multiple edges
                                     are specified, the average value will be
                                     used, unless the statistical deviation
                                     exceeds --deskew-scan-deviation. Use
                                     'left' for scanning from the left edge,
                                     'top' for scanning from the top edge,
                                     'right' for scanning from the right edge,
                                     'bottom' for scanning from the bottom.
                                     Multiple directions can be separated by
                                     commas. (default: 'left,right')

-ds --deskew-scan-size <pixels>      Size of virtual line for rotation
                                     detection. (default: 1500)

-dd --deskew-scan-depth <ratio>      Amount of dark pixels to accumulate until
                                     scanning is stopped, relative to scan-bar
                                     size. (default: 0.5)

-dr --deskew-scan-range <degrees>    Range in which to search for rotation,
                                     from -degrees to +degrees rotation.
                                     (default: 5.0)

-dp --deskew-scan-step <degrees>     Steps between single rotation-angle
                                     detections.
                                     Lower numbers lead to better results but
                                     slow down processing. (default: 0.1)

-dv --deskew-scan-deviation <dev>    Maximum statistical deviation allowed
                                     among the results from detected edges.
                                     No rotation if exceeded. (default: 1.0)

-W --wipe                            Manually wipe out an area. Any pixel in
     <left>,<top>,<right>,<bottom>   a wiped area will be set to white.
                                     Multiple --wipe areas may be specified.
                                     This is applied after deskewing and
                                     before automatic border-scan.

-mw --middle-wipe                    If --layout is set to 'double', this
      <size>|<left>,<right>          may specify the size of a middle area to
                                     wipe out between the two pages on the
                                     sheet. This may be useful if the
                                     blackfilter fails to remove some black
                                     areas (e.g. resulting from photo-copying
                                     in the middle between two pages).

-B --border                          Manually add a border. Any pixel in the
     <left>,<top>,<right>,<bottom>   border area will be set to white. This is
                                     applied after deskewing and before
                                     automatic border-scan.

-Bn --border-scan-direction          Directions in which to search for outer
     [v[ertical]][,][h[orizontal]]   border. Either 'v' (for vertical
                                     scanning), 'h' (for horizontal scanning)
                                     of 'v,h' (for both) can be specified.
                                     (default: 'v')

-Bs --border-scan-size <size>|<h,v>  Width of virtual bar used for border
                                     detection. Two values may be specified
                                     to individually set horizontal and
                                     vertical size. (default: 5,5)

-Bp --border-scan-step <step>|<h,v>  Steps to move virtual bar for border
                                     detection. (default: 5,5)

-Bt --border-scan-threshold <t>      Absolute number of dark pixels covered by
                                     the border-scan mask above which a border
                                     is detected. (default: 5)

-Ba --border-align                   Direction where to shift the detected
      [left],[top],[right],[bottom]  border-area. Use --border-margin to
                                     specify horizontal and vertical distances
                                     to be kept from the sheet-edge.
                                     (default: none)

-Bm --border-margin                  Distance to keep from the sheet edge when
      <vertical>,<horizontal>        aligning a border area. May use
                                     measurement suffices such as cm, in.

-w --white-threshold <threshold>     Brightness ratio above which a pixel is
                                     considered white.
                                     (default: 0.9)

-b --black-threshold <threshold>     Brightness ratio below which a pixel is
                                     considered black (non-gray). This is used
                                     by the gray-filter. This value is also
                                     used when converting a grayscale image to
                                     black-and-white mode (default: 0.33)

-ip --input-pages 1|2                If '2' is specified, read two input
                                     images instead of one and internally
                                     combine them to a doubled-layout sheet
                                     before further processing.
                                     Before internally combining, --pre-
                                     rotation is optionally applied
                                     individually to both input images as the
                                     very first processing steps.

-op --output-pages 1|2               If '2' is specified, write two output
                                     images instead of one, as a result of
                                     splitting a doubled-layout sheet after
                                     processing. After splitting the sheet,
                                     --post-rotation is optionally applied
                                     individually to both output images as the
                                     very last processing step.

-S --sheet-size <width>,<height>     Force a fix sheet size. Usually, the
                | <size-name>        sheet size is determined by the input
                                     image size (if input-pages=1), or by the
                                     double size of the first page in a
                                     two-page input set (if input-pages=2).
                                     If the input image is smaller than the
                                     size specified here, it will appear
                                     centered and surrounded with a white
                                     border on the sheet. If the input image is
                                     bigger, it will be centered and the edges
                                     will be cropped. This option may also be
                                     helpful to get regular sized output
                                     images if the input image sizes differ.
                                     Standard size-names like 'a4-landscape',
                                     'letter', etc. may be used (see --size).
                                     (default: as in input file)

--sheet-background black|white       Sets a color with which the sheet is
                                     filled before any image is loaded and
                                     placed onto it. This can be useful when
                                     the sheet size and the image size differ.

--no-blackfilter                     Disables black area scan. Individual sheet
  <sheet>{,<sheet>[-<sheet>]}        indices can be specified.

--no-noisefilter                     Disables the noisefilter. Individual sheet
  <sheet>{,<sheet>[-<sheet>]}        indices can be specified.

--no-blurfilter                      Disables the blurfilter. Individual sheet
  <sheet>{,<sheet>[-<sheet>]}        indices can be specified.

--no-grayfilter                      Disables the grayfilter. Individual sheet
  <sheet>{,<sheet>[-<sheet>]}        indices can be specified.

--no-mask-scan                       Disables mask-detection. Masks explicitly
  <sheet>{,<sheet>[-<sheet>]}        set by --mask will still have effect. In-
                                     dividual sheet indices can be specified.

--no-mask-center                     Disables auto-centering of each mask.
  <sheet>{,<sheet>[-<sheet>]}        Auto-centering is performed by default
                                     if the --layout option has been set. In-
                                     dividual sheet indices can be specified.

--no-deskew                          Disables deskewing. Individual sheet
  <sheet>{,<sheet>[-<sheet>]}        indices can be specified.

--no-wipe                            Disables explicit wipe-areas.
  <sheet>{,<sheet>[-<sheet>]}        This means the effect of parameter
                                     --wipe can be disabled individually per
                                     sheet.

--no-border                          Disables explicitly set borders.
  <sheet>{,<sheet>[-<sheet>]}        This means the effect of parameter
                                     --border can be disabled individually per
                                     sheet.

--no-border-scan                     Disables border-scanning from the
  <sheet>{,<sheet>[-<sheet>]}        edges of the sheet. Individual sheet
                                     indices can be specified.

--no-border-align                    Disables aligning of the area detected by
  <sheet>{,<sheet>[-<sheet>]}        border-scanning (see --border-align). In-
                                     dividual sheet indices can be specified.

-n --no-processing                   Do not perform any processing on a sheet
     <sheet>{,<sheet>[-<sheet>]}     except pre/post rotating and mirroring,
                                     and file-depth conversions on saving.
                                     This option has the same effect as setting
                                     all --no-xxx options together. Individual
                                     sheet indices can be specified.

--no-qpixels                         Disable qpixel-mode for deskewing (do not
                                     internally use a 4x bigger image when
                                     rotating).

--no-multi-pages                     Disable multi-page processing even if the
                                     input filename contains a '%' (usually
                                     indicating the start of a placeholder for
                                     the page counter).

--dpi <dpi>                          Dots per inch used for conversion of
                                     measured size values, like e.g.'21cm,
                                     27.9cm'. Mind that this parameter should
                                     occur before specifying any size value
                                     with measurement suffix. (default: 300)

-t --type pbm|pgm                    Output file type. (default: as input)

-d --depth <bits>                    Output pixel depth. (default: as input)

-T --test-only                       Do not write any output. May be useful in
                                     combination with --verbose to get informa-
                                     tion about the input.

-in --input-file-sequence            Sequence of input filename patterns which
      <file-patterns>                is repeatedly traversed while resolving
                                     input filenames. Specifying a single
                                     entry is equivalent to the first filename
                                     argument after the options-list.

-out --output-file-sequence          Sequence of output filename patterns
       <file-patterns>               which is repeatedly traversed while
                                     resolving output filenames. Specifying a
                                     single entry is equivalent to the second
                                     filename argument after the options-list.

-si --start-input <nr>               Set the first page number to substitute
                                     for '%d' in input filenames. Every time
                                     the input file sequence is repeated, this
                                     number gets increased by 1. (default:
                                     (startsheet-1)*inputpages+1)

-so --start-output <nr>              Set the first page number to substitute
                                     for '%d' in output filenames. Every time
                                     the output file sequence is repeated,
                                     this number gets increased by 1.
                                     (default: (startsheet-1)*outputpages+1)

--insert-blank <nr>{,<nr>[-<nr>]}    Use blank input instead of an input file
                                     from the input file sequence at the
                                     specified index-positions. The input file
                                     sequence will be interrupted temporarily
                                     and will continue with the next input
                                     file afterwards. This can be useful to
                                     insert blank content into a sequence of
                                     input images.

--replace-blank <nr>{,<nr>[-<nr>]}   Like --insert-blank, but the input images
                                     at the specified index positions get
                                     replaced with blank content and thus will
                                     be ignored.

--overwrite                          Allow overwriting existing files.
                                     Otherwise the program terminates with an
                                     error if an output-file to be written
                                     already exists.

-q --quiet                           Quiet mode, no output at all.

-v --verbose                         Verbose output, more info messages.

-vv                                  Even more verbose output, show parameter
                                     settings before processing.

--time                               Output processing time consumed.

-V --version                         Output version and build information.