The NOISE_HURL function introduces noise into an image by changing randomly selected pixels to random colors. Pixel change probability is determined by a parameter that controls the amount of noise introduced into the image.

Example

This example adds noise to a test image:

; Read an image:
image = BYTSCL(DIST(400))
; Add noise to the image:
image_noisy = NOISE_HURL(image, 0.2)
; Display the images side by side:
IIMAGE, image, VIEW_GRID=[2,1], VIEW_TITLE='Original', $
   DIMENSIONS=[850, 550], WINDOW_TITLE='NOISE_HURL Example', $
   /NO_SAVEPROMPT
IIMAGE, image_noisy, /VIEW_NEXT, VIEW_TITLE='Noisy'

The resulting images appear:

Syntax

Result = NOISE_HURL (Image [, Randomization] [, ITERATIONS=value] [, REPLACE_MAX=value] [, REPLACE_MIN=value] [, SEED=value])

Return Value

Result is an array of the same type and dimensions as Image.

Arguments

Image

An array containing the input image. One dimensional and two dimensional arrays are treated as single channel images. Arrays with more than two dimensions are treated as n-channel images, where the number of channels is contained in the first dimension. For example, a 3 x 200 x 200 array is a 3-channel 200 by 200 image. A 4 x 200 x 200 x 5 array is considered as a stack of five 200 by 200 4-channel images.

Randomization

A floating-point scalar in the range 0.0-1.0 that specifies the probability of replacing each pixel with a random color. 0.0 means there is no chance of replacement and 1.0 means that the pixel is always replaced. The default value is 0.5.

Note: This value specifies the probability of replacement for each pixel. It does not necessarily mean that a particular percentage of the pixels are replaced.

Keywords

ITERATIONS

Set this keyword to the number of times to apply the noise generator. A similar effect can also be achieved by increasing the value of Randomization.

REPLACE_MAX

Set this keyword to the maximum value used for the randomly-generated replacement colors. The default value is 255.

REPLACE_MIN

Set this keyword to the minimum value used for the randomly-generated replacement colors. The default value is 0.

SEED

Set this keyword to the seed value for the random number generator. This keyword is used in the same way as the SEED argument for RANDOMU.

Version History

6.4

Introduced