This technique makes use of the fact that the
"asteroid" is made up of patterns of "1's" and
"0's". These numbers can be easily summed up
and reconstructed if you know the row length and
pixel size. In this example, the first filled pixel
(upper left corner) represents itself. The
following pixel gives the number of pixels (8)
that are identical to the first one. Instead of using
9 pixels of data you only use 2. The "X's" show
unused pixels. The 10th is unfilled (equal to "0")
and followed by a series of 14 filled pixels.
Continue this exercise and determine how many pixels you save using this technique (the total number of "X's").
This is a simple example of one type of on-board
averaging. The original image is 16 by 16 (256
total) pixels. The "new" (reduced) image is 8 by 8
(64 total) pixels. You can mathematically average
the number in 4 adjacent pixels and use one value
for the "new" reduced pixel. In this example, the
first group of 4 pixels had a value of "1" thus the
averaged pixel also is "1" (1+1+1+1 divided by 4).
The 5th pixel in the first row of the reduced image
has a value less than "1" and is shaded to show
this. Likewise, the next two pixels are shaded 1/2
and 3/4 as much as the filled ones.
Continue to average these pixels and shade them in a similar way. Does this look like the original image?