Section 18.2 Understanding Image Representation
Understanding images requires understanding a set of abstractions:
Images are made up of little pixels (objects of the Pixel class), laid out on an (x,y) grid.
Each pixel contains a red value, a green value, and a blue value.
Each color value is actually a number between 0 and 255.
If a pixel has red=0, green=0, and blue=0 then the color is black since this is an absence of any color of light.
If a pixel as red=255, green=255, and blue=255 then the color is white. Try tilting the bottom of a cd in white light to see the colors in the light.
Checkpoint 18.2.2.
11-9-1: Where is x = 0 y = 0 on an image?
Middle of the image in width on the left side
y is 0 at the top left corner
Top right corner of the image
x is 0 at the left corner
Middle of the image in width and height
y is 0 at the top left corner and x is 0 on the left
Top left corner of the image
Correct! x is 0 and y is 0 at the top left corner of the image
Bottom left corner of the image
y is 0 at the top and increases towards the bottom
Checkpoint 18.2.3.
11-9-2: What color would red = 255, green = 0, blue = 0 be?
black
Black is an absence of light (all values are 0).
white
White is when all values are 255.
red
If the green and blue are 0 and the red is 255 this will be red.
green
This would be true if the green was 255 and the other values were 0.
blue
This would be true if the blue was 255 and the other values were 0.
http://csunplugged.org/image-representation
