1. FINAL Project Information
One Design Review presentations (10 minutes long)
A Final Document of your Project
Wiki Page Describing your Project
YourNameIdlGuiProject
Teaming is Encouraged
LastNamesIdlGuiProject
Winter Quarter 2003
Rolando V. Raqueño

2. Final Project
Post on the wiki, by this Thursday, a half page abstract of your intended GUI design, and the problem domain that it addresses.
Winter Quarter 2003
Rolando V. Raqueño

3. Working with Data
Winter Quarter 2003
Rolando V. Raqueño

4. Representation of Information in a Computer
All information in a computer is stored as a collection of bits
A bit, also known as a binary digit, is a number represented in base 2. It can only be either a 1 (one) or 0 (zero)
Think of information as data with structure
All the one’s and zero’s represented by the computer is data. How they are interpretted generates information (or garbage)
Winter Quarter 2003
Rolando V. Raqueño

5. Representation of Information in a Computer
Information stored in a computer can represent
Instructions
Executable Programs
Data
Numbers - integers and real values
Characters - ASCII, multinational characters
Others - imagery, sound, etc.
Winter Quarter 2003
Rolando V. Raqueño

6. Representation of Information in a Computer
Bits in a computer are usually grouped into the following units
4 bits == 1 nibble
8 bits == 1 byte or 1 ( char ) - a single character
16 bits == 2 bytes or 1 ( short int, int ) - integer value
32 bits == 4 bytes or 1 ( long int, int ) - integer value
or 1( float) - real value
64 bits == 8 bytes or 1 (double) - real value
Winter Quarter 2003
Rolando V. Raqueño

7. Representation of Information in a Computer
Numbers can be represented as either integers or real values
integers { -5, 0, 125, }
real { , , -1.0e-20, }
Text is typically represented using the ASCII character set where each character is represented as a byte value.
Winter Quarter 2003
Rolando V. Raqueño

8. Representation of Information in a Computer
Winter Quarter 2003
Rolando V. Raqueño

9. Representation of Information in a Computer
Winter Quarter 2003
Rolando V. Raqueño

10. Line Delimiters on Different Systems
In the UNIX System, lines are delimited by linefeed (also designated as nl and has an ASCII value of 012 or 10)
In MACS and PC’s, lines are delimited by carriage returns (also designated as cr and has an ASCII value of 015 or 13)
Still other systems use a combination of carriage return-line feeds to delimit lines
Winter Quarter 2003
Rolando V. Raqueño

11. Common Cross Platform File Problem
Some one gave you a text file created on a PC which you transferred to the UNIX system. You try to edit the file using vi, but vi complains that the line is too long
Solution: (A Stupid Unix Trick)
% cat old_file | tr “\015” “\012” > new_file
This command translates all carriage returns to line feeds.
Winter Quarter 2003
Rolando V. Raqueño

12. Numbering Systems
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Rolando V. Raqueño

13. Converting Number Bases
Winter Quarter 2003
Rolando V. Raqueño

14. Converting Number Bases
Winter Quarter 2003
Rolando V. Raqueño

15. Negative Number Representation
Winter Quarter 2003
Rolando V. Raqueño

16. Converting a Negative Number into Binary using 2’s Complement
Winter Quarter 2003
Rolando V. Raqueño

17. How Does This All Relate to Computers and Programming
Winter Quarter 2003
Rolando V. Raqueño

18. 1-bit Address Line and 1-bit Data Line Computer Architecture
Winter Quarter 2003
Rolando V. Raqueño

19. 2-bit Address Line and 1-bit Data Line Computer Architecture
Winter Quarter 2003
Rolando V. Raqueño

20. 1-bit Address Line and 2-bit Data Line Computer Architecture
Winter Quarter 2003
Rolando V. Raqueño

21. 2-bit Address Line and 2-bit Data Line Computer Architecture
Winter Quarter 2003
Rolando V. Raqueño

22. 8-bit Address Line and 8-bit Data Line Computer Architecture
Winter Quarter 2003
Rolando V. Raqueño

23. In General
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Rolando V. Raqueño

24. Caveat on Multi-Byte Data
When dealing with data that encompasses more than a single byte (e.g. integer value greater than 255), you must know the “endian” of the data
Endian represents how a machine interprets the significance of a set of bytes.
There are big-endian machines and little endian machines
Winter Quarter 2003
Rolando V. Raqueño

25. Caveat on Multi-Byte Data
Big Endian Machines (Suns, Motorolas) would represent the integer value 512 internally as two bytes in the following order.
MSB LSB
Winter Quarter 2003
Rolando V. Raqueño

26. Caveat on Multi-Byte Data
Little Endian Machines (DECS, Intels) would represent the integer value 512 internally as two bytes in the following order.
LSB MSB
Winter Quarter 2003
Rolando V. Raqueño

27. Caveat on Multi-Byte Data
This is typically not a problem as long as you stay on the same machine.
If you, however, start transferring data (e.g. images) in raw form from one machine to another, you will need to be aware of this situation.
You can often transpose multibyte data using the dd utility (does not work for data spanning more than two bytes)
Winter Quarter 2003
Rolando V. Raqueño

28. Working with IDL Variables
Variable names must start with a letter but can include, letters, digits, underscore or dollar characters.
Variables are not case sensitive, i.e.,
Celsius is equivalent to celsius
Winter Quarter 2003
Rolando V. Raqueño

29. Working with IDL Variables
Variables in IDL have two important attributes
Data type
Attributes
Winter Quarter 2003
Rolando V. Raqueño

30. IDL Variable Data Types
Undefined
Integer Values
Byte, Integer, Long Integer
Floating Point Values
Floating Point, Double Precision
Single Precision Complex, Double Precision Complex
String
Winter Quarter 2003
Rolando V. Raqueño

31. IDL Variable Data Structures
Scalar
Vector (one-dimensional array)
Array (up to eight dimensions)
Structure (combination of any mixture of data - Very Important in understanding Object-Oriented Programming Concepts)
Winter Quarter 2003
Rolando V. Raqueño

32. Initializing Scalar Variables
byte_variable = 0B
integer_variable = 0
long_integer = 0L
float_variable = 0.0
double_variable = 0.0D
complex_variable = Complex(0.0, 0.0)
dcomplex_variable = DComplex(0.0, 0.0)
string_variable = ‘‘
Winter Quarter 2003
Rolando V. Raqueño

33. Initializing Array Variables
byte_array = bytarr( 256, 256, 3 )
integer_array = intarr( 256, 256 )
long_array = lonarr( 256, 256 )
float_array = fltarr( 256, 256 )
double_array = dblarr( 256, 256 )
complex_array = complexarr( 256, 256 )
dcomplex_array = dcomplexarr( 256, 256)
string_array = strarr(80)
Winter Quarter 2003
Rolando V. Raqueño

34. Initializing Array Variables
Initializing Array with each element set to its subscript
bindgen, indgen, lindgen, findgen, dindgen, cindgen, dcindgen, sindgen
Only real parts of complex numbers are set to the subscripts
An array of strings containing the numbers is created by sindgen
Winter Quarter 2003
Rolando V. Raqueño

35. Initializing Array Variables
Make_array function is a general way of creating and initializing arrays
array=make_array(10,12,Value=1,/Int)
Replicate functions allows initialization of all elements of an array with a given variable (useful in structures)
initial_value = 1
array=replicate(initial_value, 10,12)
Winter Quarter 2003
Rolando V. Raqueño

36. Structures in IDL
Allows more abstract data types to be created from other basic data types
Example
Date data structure
IDL> a={date, month:0B, day:0B, year:0B}
IDL> print,a
{ }
Winter Quarter 2003
Rolando V. Raqueño

37. Structures in IDL Date Example (using a Named Structure)
IDL> a.month=12
IDL> a.day=25
IDL> a.year=96
IDL> print,a
{ }
IDL> print,a.month 12
IDL> print,a.day 25
IDL> print,a.year 96
Winter Quarter 2003
Rolando V. Raqueño

38. Structures in IDL Date Structure Example IDL> c={date}
IDL> print,c
{ }
IDL> help,c
C STRUCT = -> DATE Array(1)
Winter Quarter 2003
Rolando V. Raqueño

39. Structures in IDL Anonymous Structures
IDL> d={month:1,day:1,year:97}
IDL> print,d
{ }
IDL> e=d
IDL> print,e
Winter Quarter 2003
Rolando V. Raqueño

40. Structures in IDL Anonymous Structures
IDL> e={month:'January',day:d.day,year:d.year}
IDL> print,e
{ January }
IDL> e.month='December'
{ December }
Winter Quarter 2003
Rolando V. Raqueño

41. Structures in IDL Determining Variable Structure
IDL> help,e,/structure
** Structure <761058>, 3 tags, length=12, refs=1:
MONTH STRING 'December'
DAY INT
YEAR INT
Winter Quarter 2003
Rolando V. Raqueño

42. Structures in IDL Determining Structure Characteristics
IDL> print,n_tags(e) 3
IDL> print,tag_names(e)
MONTH DAY YEAR
Winter Quarter 2003
Rolando V. Raqueño

43. Dual Nature of IDL structures
IDL> e={month:"December", day:1, year:97}
IDL> print,e.month
December
IDL> print,e.day 1
IDL> print,e.year 97
IDL> e={month:"December", day:1, year:97}
IDL> print,e.(0)
December
IDL> print,e.(1) 1
IDL> print,e.(2) 97
Winter Quarter 2003
Rolando V. Raqueño

44. Array Manipulation in IDL
Let’s create an array representing a multiband image
IDL> image=bindgen(2,3,4)
IDL> print,image
0 1
2 3
4 5
6 7
8 9
10 11
12 13
14 15
16 17
18 19
20 21
22 23
Winter Quarter 2003
Rolando V. Raqueño

45. Array Manipulation in IDL
Extract the first and last band of the image
IDL> print,image(*,*,0)
0 1
2 3
4 5
IDL> print,image(*,*,3)
18 19
20 21
22 23
Winter Quarter 2003
Rolando V. Raqueño

46. Array Manipulation in IDL
Extracting the “color” or “spectral vector” of the first pixel
IDL> print,image(0,0,*) 6 12 18
Winter Quarter 2003
Rolando V. Raqueño

47. Array Manipulation in IDL
Assign band 1 to band 4
IDL> band1=image(*,*,0)
IDL> image(*,*,3) = band1
Shortcut
IDL> image(*,*,3)=image(*,*,0)
Winter Quarter 2003
Rolando V. Raqueño

48. Array Manipulation in IDL
Subsectioning parts of an image
IDL> print,image(0:1,0:1,*)
0 1
2 3
6 7
8 9
12 13
14 15
Winter Quarter 2003
Rolando V. Raqueño

49. Array Manipulation
where function to find indices of elements that meet certain criteria
IDL> print, where( image gt 5 and image lt 12)
Use of other arrays to index other arrays
IDL> indices=where( image gt 5 and image lt 12)
IDL> image(indices)=-1
Winter Quarter 2003
Rolando V. Raqueño