op normalize

FireSight wrapper for OpenCV normalize, which scales and shifts the dynamic range of the pixels in an image. Normalization is often used to focus on "pixel values of interest" and is a great visual aid for analyzing images..

• alpha Norm value to normalize to or the lower range boundary in case of the range normalization. Default is 1 unless image is 8-bit, in which case FireSight will automatically compute a good value.
• beta Upper range boundary in case of the range normalization; it is not used for the norm normalization. Only used for NORM_MINMAX.
• normType normalization type (NORM_L2 (default), NORM_L1, NORM_MINMAX, NORM_INF).

For 8-bit images, FireSight provides two parameters which are much more convenient to use than alpha and beta:

• domain JSON array of integers describing value interval to normalize. Default is [0,255]. Values outside this interval will be eliminated from pipeline image by truncating and shifting image values. This works for all normalization types and is useful for focusing on a value interval of interest.
• range JSON array of integers describing output value interval. Default is [0,255], which maximizes the dynamic range of the normalized output. This is rarely used.

Model

{}

Examples

The examples below use the following test image. The test image has pixel values in the range [0,255] with a background pixel value of 32.
Within the test image are letters in the grayscale range [20,52]. The letters are difficult to see with the naked eye:

Example 1: Show ABC pipeline

firesight -i img/abc.png -p json/normalize.json -o target/normalize.png

Pixel:0.6ms RPi:11ms

The default NORM_L2 normalization reveals the letters hidden in the test image.

Example 2: High Contrast ABC pipeline

firesight -i img/abc.png -p json/normalize.json -o target/normalize.png -Ddomain=[20,52]

Pixel:0.8ms RPi:14ms

By choosing a domain that matches the values used to represent the letters, we eliminate uninteresting dark/light values. This allows us to increase the image gain and bias it toward the value interval of interest:

See Also

• op absdiff
• op threshold

Example 3: normType and domain

The following table illustrates the utility of the various normType options. It also shows how the domain interval can improve contrast.

&nbps;
normType	no domain	domain=[20,52]	no domain	domain=[164,196]
NORM_MINMAX
NORM_INF
NORM_L1
NORM_L2