CSC151 2007S, Class 40: Color Palettes

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* Assignment 14 (A Procedure is Worth A Thousand Pictures) is now ready.
* The Project Description is now ready.
* Reading for Thursday: Vectors.
* Reminder: EC for Thursday's Thursday Extra

Overview:
* Saving space with palettes.
* Choosing palette colors.
* Using different palettes.

Writing images to a file
* For each position in sequence, write the position and color
* Can also do so without the positions, as long as the order is known.
* If we're going to write all the colors, we should do so as
  efficiently as possible.

Past techniques:
* Write the number that represents the color:
  * Hard to read
  * Lots of characters (up to 10 per color)
* Represent the color as RGB values
  * Easier to read
  * Lots of characters (up to 12 per color)
* Represent the color as RGB values, with each RGB value represented
  by a single character
  * Fewer characters (exactly 3 per color)
  * Essential unreadble by humans (easy for computers)

Today: Can we do better?
* Still using the model that we're writing each color separately.
* For an 8x8 image, we need only write 64 values (vs. 192 for the previous
  model)

* By using a limited number of colors (chosen in some way), we can represent
  images more efficiently.
* Technique: Palettes

* What if there are more colors in the image than in the palette?
  * Scale the values
  * APPROXIMATE THE IMAGE