The previous post: review of JavaScript syntax basics
Function
A function consists of three elements:
- function name
- parameter
- return
Example 1. frame an image with black border:
Example 2. more red:
Example 3. crop two images of different sizes:
Example 4. enlarge the image:
note: the top left pixel is at position (0,0)
http://www.dukelearntoprogram.com/course1/enlarge2/
Steganography
- Rationale
The idea is that you have image A and image B, and you want to hide image B inside A. Suppose A is 10111100, B is 11011001. You would take 1011 from A and 1101 from B (use 16=2^4 to get those numbers). Then, we can combine them into 10111101 and get the new image with a hidden image in it!
pa: pixel for image A
npa: the new pixel for image A
pb: pixel for image B
npb: the new pixel for image B
npa. setRed(Math.floor(pa/16) * 16)
npb. setRed(Math.floor(pb.getRed()/16))
- complete coding example:
http://www.dukelearntoprogram.com/course1/steganography/
