Image Data and Display

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Image Data and Display
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For Class Consistency

• source rvrpci/.simg726.rc

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Quiz 2 Topics

• mkdir
• chmod
• cd
• grep
• ci and co

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PBMPLUS FORMAT and xv

• Digital image format concepts
• PBMPLUS image interchange format.
• Displaying digital image
• xv image display

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PBMPLUS Image Data Types

• Bilevel Image Data Type
• Black and White
• Monochrome Image Data Type
• Greyscale
• RGB Color Image Data Type
• Color

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Two PBMPLUS Representations

• All PBMPLUS data formats have the following
  representations
• ASCII Format
• (for Human Consumption)
• RAW Format
• (for Computer Consumption)

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Displaying Images

• Use xv utility for display and documentation
  purposes.
• Note that xv is an X client
• Should NEVER be used for image processing
• USE ONLY FOR DISPLAY PURPOSES
• To invoke xv
• xv
• xv filename.pgm

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Portable Bit Map (PBM)

• Bilevel Image Data Type
• (Black and White)
• Used to represent printed black and white imagery
  such as documents and faxes.
• Uses 0s (zeroes) to represent white
• (no ink deposited on paper)
• Uses 1s (ones) to represent black
• (ink deposited on paper)

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Let us digress The vi Problem

• vi practice and creation of a bilevel image.
• 7x10 graph paper divided into 10 squares per
  inch.
• Cell not covered by ink
• value of zero (0).
• Cell fully or partially covered by ink
• value of one (1).
• You will have a total of 700 pixels to enter.

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Problem 1 Solution

• vi - Brute Force Solution
• 1. Is the current pixel 0 (zero) or 1 (one)?
• 2. Type the appropriate character
• 3. Repeat steps 1 and 2 until done

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Problem 1 Solution

• vi- Smart Solution
• 1. Type the vi command 70i0
• seventy, i - for insert, 0 (zero)
• 2. Hit the ESCAPE key to get you out of insert
  mode.
• 3. Type the vi command o to open a new line
• 4. Hit the ESCAPE key to get you out of insert
  mode.
• 5. Move back up to the line of zeroes and use the
  yy (yank command) to make a copy of the line of
  70 zeroes.

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Problem 1 Solution

• vi- Smart Solution
• 6. Type the vi command p 10 times
• 7. Move back up to the top line of zeroes and use
  the 10yy (yank command) to make a copy of 10
  lines of 70 zeroes per line.
• 8. Type the vi command p 10 times
• 9.You will now have a page of 700 zeroes.

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Problem 1 Solution

• vi- Smart Solution
• 10. You can navigate to the areas that need to be
  changed to 1 and use the R command to replace
  contiguous set of characters.
• 11. Hit the ESCAPE key to get you out of insert
  mode.
• 12. Navigate to next section and repeat steps 10
  -12 until done.
• 13. Save the file out and exit vi
• wq signature.dat

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Yet another vi Digression

• To show line number in vi, execute the following
  command
• set number
• To disable line numbers in vi, execute the
  following command
• set nonumber

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Viewing current vi settings

• set all
• noautoindent nomodelines
  noshowmode
• autoprint nonumber
  noslowopen
• noautowrite nonovice
  tabstop8
• nobeautify nooptimize
  taglength0
• directory/var/tmp paragraphsIPLPPPQPP
  LIpplpipnpbtagstags /usr/lib/tags
• noedcompatible prompt
  tagstack
• noerrorbells noreadonly
  termvt220
• noexrc redraw
  noterse
• flash remap
  timeout
• hardtabs8 report5
  ttytypevt220
• noignorecase scroll11
  warn
• nolisp sectionsNHSHH HUuhshc
  window23
• nolist shell/bin/csh
  wrapscan
• magic shiftwidth8
  wrapmargin0
• mesg noshowmatch
  nowriteany

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Saving vi Preferences

• Preferences such as set number can be saved in
  the file .exrc in your home directory ()

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A vi Command to Always Remember

• To replace all occurrences or a string in a file
  with new string.
• s/string1/string2/g
• OR
• s/string1/string2/gc
• (Will ask you for confirmation)

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The Super-smart Solution

• In UNIX
• repeat 70 echo -n 0 gtgt one_line echo gtgt
  one_line repeat 100 cat one_line gtgt
  signature.dat

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Lets Create another image

• Put the signature.dat away for the time being and
  create a simpler image
• Call it bilevel.pbm

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Portable Bit Map (PBM)

• Bilevel Image Data Type
• For the ASCII file format, the file header is
  given by P1
• width and height of the image.
• Comments are indicated by the character
• P1
• This is a 16 column x 3 row
• PBM ASCII image
• Created by using vi
• 16 3
• 001010100011010000111110
• 010010000101001001011100

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Portable Bit Map (PBM)

• Make a copy of bilevel.pbm and edit the copy to
  look like the following,
• P1
• This is a 16 column x 3 row PBM ASCII
• image
• 16 3
• 0010101000110100
• 0011111001001000
• 0101001001011100

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Portable Bit Map (PBM)

• When displayed looks like
• P1
• This is a 16 column x 3 row PBM ASCII
• image
• 16 3
• 0010101000110100
• 0011111001001000
• 0101001001011100

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How to Add a PBMPLUS Header to an Image File

• If its an ASCII file you can use vi
• Use the cat command to concatenate a header from
  a file or the keyboard (standard input - stdio)

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Put a header on signature.dat and display in xv

• Method 1
• Using a text editor, input the appropriate header
  values.

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Put a header on signature.dat and display in xv

• Method 2
• Edit a file called header.dat containing the
  header information
• Concatenate the header file at the beginning of
  signature.dat using the cat command
• cat header.dat signature.dat gt signature.pbm

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Put a header on signature.dat and display in xv

• Method 3
• Concatenate the header data from the keyboard
  directly to the beginning of signature.dat using
  the cat command
• cat - signature.dat gt signature.pbm
• P1
• 70 100
• D

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Portable Bit Map (PBM)

• There is also a binary version of the PBM image
  type which uses a P4 header such as the one below
• P4
• This is a 16 column x 3 row PBM RAW
• image
• 16 3
• 4gtHR\

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Portable Grey Map (PGM)

• Monochrome Image Data Type (Greyscale)
• Displayed greyscale imagery
• Grey values µ brightness.
• Convention opposite that of the PBM format

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Portable Grey Map (PGM)

• Monochrome Image Data Type (Greyscale)
• EXAMPLE,
• P2
• This is a 3 column x 2 row PGM ASCII image
• With a possible maximum grey value of 255
• 3 2
• 255
• 42 52 62
• 72 82 92

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Portable Grey Map (PGM)

• When displayed, the image is shown below
• P2
• This is a 3 column x 2 row PGM ASCII image
• With a possible maximum grey value of 255
• 3 2
• 255
• 42 52 62
• 72 82 92

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Portable Grey Map (PGM)

• There is also a binary version of the PGM image
  type which uses a P5 header such as the one below
• P5
• This is a 3 column x 2 row PGM Raw
• image
• 3 2
• 255
• 4gtHR\

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Portable Pixel Map (PPM)

• RGB Color Image Data Type (Color)
• Red, Green, and Blue bands
• Arranged in pixel-interleaved format or band
  interleaved by pixel (BIP)

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Portable Pixel Map (PPM)

• RGB Color Image Data Type (Color)
• For the ASCII file format,
• P3
• width, height
• maximum grey level possible of the image
• The pixel values are given as a triple
  representing the red, green, and blue components .

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Portable Pixel Map (PPM)

• RGB Color Image Data Type (Color)
• EXAMPLE,
• P3
• 3 3
• 255
• 255 0 0 0 255 0 0 0 255
• 128 0 0 0 128 0 0 0 128
• 0 0 0 128 128 128 255 255 255

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PPM QUESTION

• So what does the data4gtHR\ look like as a Raw
  PPM Image?

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Conversion of Raw Files to PBMPLUS Format

• Alternative to manually prepending a header file
  using cat command
• rawtopbm, rawtopgm, or rawtoppm
• rawtopgm 256 256 rvrpci/pub/MyCat_P5.raw gt
  MyCat.pgm

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Usage Note About PBMPLUS Commands

• PBMPLUS commands heavily use the UNIX redirection
  and piping
• To get help use -h option.
• rawtopgm -h
• usage rawtopgm -headerskip N -rowskip N
  -tb-topbottom ltwidthgt ltheightgtrawfile

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Converting PNM Image File to Another Format

• PNM is a generic designator for all PBM, PGM, and
  PPM
• Convert a PBMPLUS format file into a TIFF
• e.g., signature.pbm to signature.tiff.
• Use the following command
• pnmtotiff -none signature.pbm gt signature.tiff
• -none option means not invoke LZW image
  compression.

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Rudimentary Image Processing Using the PBMPLUS
Utilities

• Requires that all input be in some form of PBM,
  PGM, PPM image
• Supposed we wanted to enlarge a tiff file ( e.g.,
  signature.tiff) by a scale factor of 2x and then
  convert it to a SUN raster file.

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Rudimentary Image Processing Using the PBMPLUS
Utilities

• The previous process can actually be executed in
  one UNIX command
• tifftopnm signature.tiff pnmscale 2.0
  pnmtorast gt signature.rast
• In fact you can pipe the information directly to
  xv before writing it out to another format
• tifftopnm signature.tiff pnmscale 2.0
  pnmtorast xv -

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PBMPLUS File Information

• Supposed you wanted to know what the
  characteristics are of a particular PBMPLUS file
  you can give the following command
• pnmfile MyCat.pgm
• MyCat.pgm PGM raw, 256 by 256 maxval 255

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PBMPLUS Histogram Utilities

• Greyscale histogram
• pgmhist
• Color histogram
• ppmhist

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Cutting out regions of interest

• pnmcut
• usage pnmcut x y width height pnmfile
• pnmcrop
• usage pnmcrop -white-black -left -right
  -top -bottom pnmfile

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Pasting or Arranging Images

• pnmcat
• pnmcat -white-black -leftright-lr
  -jtop-jbottom pnmfile pnmfile ...
• pnmpaste
• pnmpaste -replace-or-and xor frompnmfile x y
  intopnmfile

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You have a bunch of images...

• pnmindex
• pnmindex -size N -across N
• -colors N -black pnmfile ...

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Color Bands Combination and Extraction

• rgb3ppm
• rgb3toppm redpgmfile greenpgmfile bluepgmfile
• ppmtorgb3
• ppmtorgb3 ppmfile
• results in .red .grn .blu

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Spatial Operations

• pnmconvol
• pnmscale
• pnmrotate
• pnmflip
• pnmshear

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Greyscale/Color Operations

• ppmquant
• pnmdepth
• ppmdither

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Really Useful Stuff

• Doing Screen Captures under X
• xwd xwdtopnm pnmdepth 255 pnmtotiff gt
  screen.tif
• Your cursor will turn into crosshairs
• Click on the window you want to capture

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Screen Capture through xv

• Click on grab button
• Specify a time delay
• Left button grabs window
• Middle button grabs a rectangle
• Right button cancels

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Getting Hardcopy Output

• Determining what type of display device you have
• IDLgt help,/device
• Available graphics_devices CGM HP MAC NULL PCL
  PS Z
• Current graphics device MAC
• Macintosh Quickdraw Driver
• Screen Resolution 640x442
• Physical Color Map Entries (Used / Total)
  220 / 256
• Current Window Number 0, size (320,240)
  type Window.
• Graphics Function 3 (copy)
• Current Font Chicago
• Default Backing Store Pixmap.
• Window Status
• 0 Window 320x240 (Retained)

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Getting Hardcopy Output

• To get a postscript output of your plot
• IDLgt set_plot,ps
• IDLgt device, Filenamenew_plot.ps
• IDLgt plot, my_data,TitleImaging Lab 1
• IDLgt device, /close
• IDLgt lpr -Pdip new_plot.ps
• You then want to return your output device to
  whatever display device you had originally
• IDLgt set_plot,MAC

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Check Your Postscript File Before Sending to the
Printer

• You can use the ghostview utility to view a
  postscript file

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Note Well

• Always make sure that the printer to which you
  will be sending your job is capable of talking
  Postscript. If it does not, you will be killing
  many trees.
• To find out the status of your job
• lpq -P(printer name)
• To kill a print job
• lprm -P(printer name) job_number

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Getting Encapsulated Postscript File (EPS)

• To get a postscript file of your plot that you
  can include into another document
• IDLgt set_plot,ps
• IDLgt device, /encapsulated, /preview
• IDLgt device, Filenamenew_plot.eps
• IDLgt plot, my_data,TitleImaging Lab 1
• IDLgt device, /close
• The above process creates what is known as an
  Encapsulated Postscript File (EPS)

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