IDL - Data Input & Output

NCKU Phys. Cheng-Ling KuoJohnny@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 FilesBinary FilesImage FilesWAV 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 IOName Years Salary-------------------------Johnny 2002 2000.5Ted 2003 1000.5Ken 2001 1500.5

CommandIDL>openr, 1, "D:\doc\ 教育訓練及展示 \IDL\io\format.txt“IDL>head=‘’IDL>name=‘’ & yy=0L & ss=0.0IDL>readf, 1, format="(A30)", headIDL>readf, 1, format="(A10, 1X, I4, 4X, F10.5)", name, yy, ssIDL>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 environmentSupported Devices

CGM Computer Graphics MetafileHP Hewlett-Packard Graphics Language (HP-GL)LJ Digital Equipment LJ250 (VMS Only)MAC Macintosh displayMETAFILE Windows Metafile Format (WMF)NULL No graphics outputPCL Hewlett-Packard Printer Control Language (PCL)PRINTER System printerPS PostScriptREGIS Regis graphics protocol (DEC systems only)TEK Tektronix compatible terminalWIN Microsoft Windows X X Window SystemZ 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 depthIDL>device, get_visual_depth=depthIDL>print, depth

The color system

TrueColor (16-, 24-, or 32-bit)-DefaultIDL>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)’xlIDL>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 colorIDL>READ_JPEG, 'E:\RSI\IDL54\examples\data\rose.jpg', img24 Color tableIDL>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 colorIDL>Device, decomped=1IDL>Tv, img24, true=1

Color tableIDL>Device, decomped=0IDL>tvlct, r, g, bIDL>Tv, img8

Read screen

True colorIDL>Img24=tvrd(true=1)

Color tableIDL>tvlct, r, g, b, /getIDL>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 = psIDL> SET_PLOT, “ps”

Setup device parametersIDL> DEVICE, file=“test.ps”, /color, /landscape

PlotIDL>TVLCT, [0,255,0,0], [0,0,255,0], [0,0,0,255]IDL> PLOT, [0,1], color=1

Close deviceIDL> DEVICE, /close

Printer Device

Set device = printerIDL> set_plot, “printer”

Setup printerIDL>p= DIALOG_PRINTERSETUP()IDL>j=DIALOG_PRINTJOB()

PlotIDL>TVLCT, [0,255,0,0], [0,0,255,0], [0,0,0,255]IDL> PLOT, [0,1], color=1

Close deviceIDL> device, /CLOSE_DOCUMENT