IDL - Data Input _ Output

							IDL - Data Input & Output
NCKU Phys. Cheng-Ling Kuo
Johnny@phys.ncku.edu.tw
Data IO
  Data Stream
     Input: keyboard, input device
     Output: terminal, printer
  File – data is read from file and write to
  a file
     Types: data, image, and any type of
      signals
IDL - File types
  ASCII Files
  Binary Files
  Image Files
  WAV Audio Files
ASCII & Binary
  ASCII
     Slower
     Portable
     Need more memory size
     Edited directly
  Binary
     Efficient
     Not portable
     Compact
     Not directly human readable
The two level of IDL‟s IO
  High-Level
     Easy using and time efficient
     Inflexible
  Low-Level
     Difficult and time-consuming
     Flexible
High-Level IDL‟s IO
  Function list
     File:
        read_ascii(ascii_template)
        read_binary(binary_template)
     Image
        read_bmp, read_jpeg, read_tiff
     Sound
        read_wave
Low-level IDL‟s IO
  LUN(logic unit number)
     File support limit 2.3 GB
        Adress up to 2^31-1 bytes (32-bit program)
     Range –2 to 128
     0, -1, -2 are stdin, stdout, stderr
     1-99: user specified
     100-128: managed by GET_LUN and
      FREE_LUN
Low-level IDL‟s IO
  Formated / Unformatted
     Formated
       readf(read), printf(write)
     Unformatted
       readu, writeu
Low-level IDL‟s IO
  Manipulate files
     Open files: openr, openw, openu
     Get detail information: fstat
     Position the file pointer(unit byte): point_lun
     Check end-of-file: eof
     Close files: close
     IDL current open files: help, /files
Low-level IDL‟s IO
  Format
     Fortran style
        A(Character), D(double), F(float), I(integer), O(octal),
         Z(Hexadecimal)
        print, !PI, format='("I guess pi value is ", 1X, F24.12)'
     C style
        %C(Character), D(double), F(float), I(integer), O(octal),
         Z(Hexadecimal)
        print, !PI, format='(%"I guess pi value is %12.4f")'
Low-level IDL‟s IO
  Formatted IO
  Name         Years Salary
  -------------------------
  Johnny       2002 2000.5
  Ted        2003 1000.5
  Ken        2001 1500.5
  Command
  IDL>openr, 1, "D:\doc\教育訓練及展示\IDL\io\format.txt“
  IDL>head=„‟
  IDL>name=„‟ & yy=0L & ss=0.0
  IDL>readf, 1, format="(A30)", head
  IDL>readf, 1, format="(A10, 1X, I4, 4X, F10.5)", name, yy, ss
  IDL>Close, 1
Low-level IDL‟s IO
  Unformatted IO
     Not portable because various machines
      have different the representation of binary
      data
     XDR(portable)
        Add extra bookkeeping information to stored in
        the file
Image Input&Output
 IDL‟s Image Representation
     Pixel: byte(0-255)
     Color System
        RGB(Red, Green, Blue)
        HLS(Hue, Lightness, and Saturation)
        HSV(Hue, Saturation, and Value)
Device
  Device means graphics environment
  Supported Devices
  CGM        Computer Graphics Metafile
  HP         Hewlett-Packard Graphics Language (HP-GL)
  LJ         Digital Equipment LJ250 (VMS Only)
  MAC        Macintosh display
  METAFILE   Windows Metafile Format (WMF)
  NULL       No graphics output
  PCL        Hewlett-Packard Printer Control Language (PCL)
  PRINTER    System printer
  PS         PostScript
  REGIS      Regis graphics protocol (DEC systems only)
  TEK        Tektronix compatible terminal
  WIN        Microsoft Windows
  X          X Window System
  Z          Z-buffer pseudo device
Device
  select the graphic device
     Set_plot, “win”
     To check the system variable, !d.name
Device
  Most keywords to the DEVICE
  procedure are sticky ?that is, once you
  set them, they remain in effect until you
  explicitly change them again, or end
  your IDL session.
Device(win)
  It can do?
     VISUAL_DEPTH – color system
     Font
     Graphic function
Device(win)
  Which‟s your system‟s graphics
  environment
     24bits
     16bits
     8bits
  Get your system‟s visual depth
  IDL>device, get_visual_depth=depth
  IDL>print, depth
The color system
  TrueColor (16-, 24-, or 32-bit)-Default
   IDL>device, decomposed=1
    Image
      IDL>READ_jpeg,'C:\Documents and Settings\johnny\My
      Documents\My Pictures\Sample.jpg', img)
      IDL>TV, img, true=1
     color indices to be interpreted as 3, 8-bit color
      indices, „(bbggrr)‟xl
      IDL>PLOT, [0,1], col=„ff0000‟xl
  ColorTable(8bit)
   IDL>device, decomposed=0
      (the least-significant 8 bits of the color index value to be
      interpreted as a PseudoColor index)
Color table
  Set palette
     loadct, xloadct
  Show palette
     xpalette
  Get color values of palette
     tvlct, r, g, b, /get
Image Input
 Functions list:
    read_bmp, read_jpeg, read_gif, read_tiff
 Example
    True color
 IDL>READ_JPEG, 'E:\RSI\IDL54\examples\data\rose.jpg', img24

    Color table
 IDL>img8 = READ_TIFF('E:\RSI\IDL54\examples\data\examples.tif', r, g, b)
 IDL>img8 = READ_PNG("E:\RSI\IDL54\examples\data\avhrr.png", r, g, b)
 IDL>img8 = READ_BMP("c:\winnt\Greenstone.bmp", r,g,b)
Image display
  True color
  IDL>Device, decomped=1
  IDL>Tv, img24, true=1
  Color table
  IDL>Device, decomped=0
  IDL>tvlct, r, g, b
  IDL>Tv, img8
Read screen
  True color
  IDL>Img24=tvrd(true=1)
  Color table
  IDL>tvlct, r, g, b, /get
  IDL>img8=tvrd()
Image Output
 Functions list:
    write_bmp, write_jpeg, write_gif, write_tiff
 Example
    True color
     IDL>WRITE_TIFF, „test.tif', TVRD(true=1)
     IDL>WRITE_JPEG, „test.jpg', TVRD(true=1), true=1
     IDL>WRITE_BMP, "test.bmp",img24, /rgb

    Color table
     IDL>WRITE_TIFF, „test.tif', TVRD(), red=r, green=g, blue=b
     IDL>WRITE_BMP, "test.bmp",img8, r, g,
     IDL>WRITE_PNG, "test.png",img8, r, g, b
Postscript Device
  Set device = ps
  IDL> SET_PLOT, “ps”
  Setup device parameters
  IDL> DEVICE, file=“test.ps”, /color, /landscape
  Plot
  IDL>TVLCT, [0,255,0,0], [0,0,255,0], [0,0,0,255]
  IDL> PLOT, [0,1], color=1
  Close device
  IDL> DEVICE, /close
Printer Device
  Set device = printer
  IDL> set_plot, “printer”
  Setup printer
  IDL>p= DIALOG_PRINTERSETUP()
  IDL>j=DIALOG_PRINTJOB()
  Plot
  IDL>TVLCT, [0,255,0,0], [0,0,255,0], [0,0,0,255]
  IDL> PLOT, [0,1], color=1
  Close device
  IDL> device, /CLOSE_DOCUMENT