Graphics Reference
In-Depth Information
we can express this weighted sum as
width of
2* 1,
n
+
n
n
∑
∑
FP
ij
*
ij
i n
=−
j n
=−
There are some general properties that filters may have. Filters are often
square matrices, usually of odd size, so we can often talk about a 3 × 3 or
5 × 5 filter. The sum of the weights in the filter is often one, especially when the
overall content of an array is to be preserved, so applying a filter usually does
not change the overall magnitude of whatever the filter is applied to.
Image Blurring
Image blurring can be done by applying a simple symmetric filter to the image,
so that each pixel's color is influenced by the color of each of its neighbors. You
can use a simple 3 × 3 blur convolution filter like the one below or a larger 5 × 5
blur convolution filter like the 5 × 5 example shown above:
121
242
121
1
16
*
.
Figure 11.5.
An original image (left) blurred by a 3 × 3 filter (center) and a 5 × 5 filter (right).
