3D
3D Photo Gallery (Part 1)
3D Photo Gallery (Part 2)

Audio
Poor Man's MIDI
Make A Metronome
iPod Tricks (Part 1)
iPod Tricks (Part 2)
iPod Tricks (Part 3)
Laugh Track Machine
Audio Player with Reverb
Shepard Melody
RB Phone Home
Build a Drum Machine

Custom Controls and Windows
Double Click Listbox
Draggable Metal Window
Double Click Canvas
Custom Buttons
Custom Buttons Part II
iTunes-style Listboxes
Custom Controls


General RB
Scrolling Windows
Using Mesage Dialogs
Case-Sensitive Word Finder
Introduction to Stacks
Wiggle Window
JPEG in PDF
Listbox Checkboxes
Background Applications
Listbox Auto-Find
Virtual Volumes
Time Tracker
Software Distribution (Part 1)
Software Distribution (Part 2)
Software Distribution (Part 3)
Software Distribution (Part 4)
Exceptions
Tips and Tricks
Text Clippings Made Easy

Graphics
Drawing a Simple Gradient
The SpriteSurface: Space Game
Image Spinner
Cropping Graphics (Part 1)
Cropping Graphics (Part 2)
Cropping Graphics (Part 3)
Cropping Graphics (Part 4)
Shimmer Graphics
Lissajous Figures
Simple Screen Capture
Vector Graphics
Kaleidoscope Images
Stegonography
Spirals!
Image Table
RB Magnifying Lens
Screen Capture
Color Picker Tutorial

Hacks
Ghost Grab
Speedy Mouse Extension
iTunes Plugins
iTunes Skinner

Mac OS X
Global Hot Key Event (Carbon Events)
Login Welcomer (Carbon Events)
Add/Remove Buttons
Resizable Sheets
Mac OS X Preferences Window
Using Sheets in REALbasic
Build a Bundle (Part 1)
Build a Bundle (Part 2)
Dock Your Passwords
Mac OS X Debugging
REALbasic Mac OS X Icon Tutorial
Animate Your Dock
RB and the Command Line

Menus
Window Menu
Templates Menu
Listbox Menu

Novelty
Guessing Game
Calendar Trivia
Tile Mixer
Zip Code Finder
Happy Valentine's Day
Merlin Simulator (Part 1)
Merlin Simulator (Part 2)
Merlin Simulator (Part 3)
Buzzword Machine
AppleSoft BASIC

Printing
Print to PDF

Registration
Registration Code Validation
Network Registration Codes

Resources
Picture Extractor (Part 1)
Picture Extractor (Part 2)

Serial
Caller ID (Part 1)
Caller ID (Part 2)
Caller ID (Part 3)

Speech
Speech Recognition

Socket Communication
Easy Peer-to-Peer File Sharing
MacPAD Version Checking
Display Web Image In Canvas
HTML IMG Tags
Version Tracking
Even Smarter Instant Messaging
Web Tiler
JavaScript and REALbasic
Stock Ticker (Part I)
Stock Ticker (Part 2)
AIM Mate

XML Manipulation
Simple XML Introduction

Video
Big Brother Video Capture

Note: All articles without a byline were written by Erick Tejkowski. When cleaning the site I removed them because the code differed from page to page, and I have yet to put them back in.

REALbasic for Dummies
by Erick Tejkowski

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Stegonography 02-28-02

Stegonography is the discipline of hiding information in files. Today we will build a simple stegonography machine. With it you can hide a secret message within an image. Give the decoder to your friends or family and they can read your secret message.

Intro

If you would like to know more about the study of stegonography, the web has many resources about the topic. This introduction is a good start if this is a new topic to you. The basic idea behind stegonography is that you can hide data within various types of computer files. Since presumably no one is looking for this data in the place or manner you hid it, the data remains secret. Only those who know your method or who have a decoder can retrieve the information from its hiding place. To demostrate, we are going to hide a short message (<100 characters long) within a 100x100 image.

Build the Interface and Add the Code

Launch REALbasic, open Window1 and add the following items:

• Canvas
• PushButton - named "EncodeButton"
• PushButton - named "DecodeButton"
• EditField - LimitText = 99

Next create two properties, by selecting the Edit-NewProperty menu:

		p as Picture
		r as RGBSurface  
	

Navigate to the Paint event of Canvas1 and enter the following code

	g.drawpicture p,0,0
	

Then, enter this code into the Open event of Window1.

  dim i,j as integer
  dim r as rgbSurface
  
  p=newpicture(100,100,32)
  r=p.rgbSurface
  
  for i=0 to 99
    for j=0 to 99
      r.Pixel(i,j) = rgb(rnd*255,rnd*255,rnd*255)
    next 
  next

Add this code to the Action event of the EncodeButton:

  dim i,n as integer
  dim s as string
  dim f as folderItem
  
  //the message
  s=editfield1.text 
  //length of the message
  n=len(editfield1.text)
  
  //write the length of the msg
  //in pixel (0,0)
  p.graphics.pixel(0,0) = rgb(n,n,n)
  
  for i=1 to n
    
    //find the ascii number of each
    //character in the message
    n = asc(mid(s,i,1))
    
    //set the red portion of
    //successive pixels to the ascii
    //value of that position's character
    p.graphics.pixel(i,0) = rgb(n,rnd*255,rnd*255)
    
  next
  
  //save the encoded picture message
  //as a PICT file.
  f = GetSaveFolderItem("image/x-pict","Encoded Image")
  if f<>nil then
    f.saveAsPicture(p)
  end if
  
  editfield1.text=""
  canvas1.refresh 
  

Finally, place this code in the Action event of the DecodeButton:

  dim i,n as integer
  dim s as string
  dim f as folderItem
  dim c as color
  dim pp as picture
  
  //save the encoded picture message
  //as a PICT file.
  f = GetOpenFolderItem("image/x-pict")
  if f<>nil then
    //open a picture
    pp = f.openAsPicture
    
    //draw this new picture
    //on the canvas
    p.graphics.drawpicture pp,0,0
    r=p.rgbSurface
    c = r.Pixel(0,0)
    canvas1.refresh 
    
    //find the red value
    //of the pixel (0,0)
    n = c.red
    
    editfield1.text=""
    for i=1 to n
      //loop thru the pixels in the top row
      //and build ascii characters based on
      //the red value of each pixel
      s = chr(r.pixel(i,0).red)
      editfield1.text = editfield1.text+s
    next
    
  end if
  
  

Conclusion

That's it! Select Debug-Run to test your work. Enter a message in the EditField and press the EncodeButton. You will be asked to save the resulting image to your hard drive. Later, press the DecodeButton to open the encoded image file and the decode the message within. Some important things to rememeber for this project:

• Save the image in PICT format only. If you try to save the image in something like JPEG, you stand the chance of altering your hidden message. The PICT format will retain the color information, which is vital here.
• There are many other ways to hide your message in the image. Try writing the message in diagonal lines through the image, by using every other pixel, or by manipulating color information. As you can see, the possibilities are limitless and devising a sophisticated design will only protect your data that much more.

The completed project might look something like this:

You can download the finished product here. See you next week!

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