In this section we will discuss how to apply and add various types of noise to image. Some noise effects can be obtained in by warping actions disturb and motion while more controlable noise is discussed in this section. There are two types of noise introduced: pixels distribution and Perlin type noise.

Pixels Distribution
Under this group, there are three type of noise: pixels, lines and crossing over All these methods have in common one thing: pixel color from one (x,y) point is actually distributed (copied) to another position in more or less random maner. With this noise group there are some control parameters associated:

Repeat radio button is used to specify if pixel will be distributed from the same (x,y,) point around with given range and repeated through specified number of iterations.

Propagate radiobutton is used to distribute pixel always from a new point. First, pixel is distributed (copied) to some (x1,y1) point and then from that point will be propagated to another randomly calculated point (x2,y2). Now, newly calculated point becomes starting point for new distribution.

Tree radiobutton is also used to propagate some pixel to new positions, but every time the pixel is copied, it's actually copied on two new positions instead of one: (x1, y1) , (x2, y2). Now, from those new position, pixel is again copied on two new positions:
(x1,y1) -> (x11,y11) , (x12,y12) and
(x2,y2) -> (x21,y21), (x22, y22). In this way, pixel is propagated in tree-like manner.

Range decrease checkbox is used to decease range after every iteration. If this box is unchecked, no decreassing is performed.

Leaves only checkbox is used to force only final leaves drawing. This is useful in combination with tree operation mode, when not the whole tree propagation is visible, but only terminal branches (leaves).

Step edit field is used to specify amount of pixel skipping. When step is higher then one, not all pixels in image are distributed. Higher the step, more pixels are skipped and faster rendering is performed.

Range edit field is used to specify maximum length between starting point and first distribution point.

Iterations edit field is used to specify a number of repeatedly distributions.

Now, something about methods contained in first noise group:

Pixels method distributes pixels from starting point according to parameters specified. Distributed pixels are not connected in any way. They are simply copied to another location in a maner controled by control parameters.

Lines method calculates a new point for scaned pixel and connects these two points by a line of size 1. This method gives very nice noisy effect when combined with tree option.

Crossing over method is actually a method taken from genetic algorithms. It performs color crossing over of starting pixel and pixel found on new, randomly calculated position. This process is not controled by any fitness function. Pixels color are crossed over by one randomly calculated cross over point. After cross over point is calculated, rightmost pixels color bits are interchanged between those two pixels. For more information on this topic, refere to articles describing genetic algorithms topic.

Perlin Type Noise
Under these group, there are few methods with one thing in common: all these methods use seamless kernel of given size (40x40 by default) with random floating point numbers in the range (0,1). These numbers actually represent intensity factor used for multiplying colors accorind the given color scheme. With this group a few control parameters are associated:

8va edit field specifies how many octaves will be taken in account when calculating turbulence.

Scale edit field specifies how deep we will zoom in given kernel.

Kernel button is used to recalculate kernel with given size. Clicking this button a new form pops up, where you can specify a new size for kernel.

Normalize checkbox is used to force turbulence normalization, i.e. to keep calculated turbulence in the range (0,1). When unchecked, normalization is not performed. You can play a bit with this option to see different results for different methods.

Color scheme listbox is used to specify a drawing method that will be performed on the image while caculating noise factors.

• Mixed BF - creates gradient from background to foreground color. Given the noise factor color is calculated by interpolating color values from 0-background to 1-foreground.
• Gradient - uses predefined color gradient. Noise factor is multiplied by 255 and is used as index to gradient palette.
• Intensity - noise factor calculated is multiplied with existing pixel color of an image.
• Save as mask - noise factors are scaled from 0 to 255 and these values are saved as mask applying in the same time mask*image rendering. If bump box for brush is checked, image bumping will also be applied.

Linear 2D method is the simpliest method in this group. 8va value does not play any role here, because no turbulence is calculated. Scale factor is used to zoom in the given kernel. This method is useful when applied with some higher scale factor.

Turbulence method adds turbulence to linear 2D noise. The number of turbulence superimposed depends on given 8va number. Higher the number, higher turbulence will be introducet.

Marble method takes the sine function of calculated turbulence, creating a marbel intensity pattern. With normalize box unchecked, more noisy look can be obtained.

Skin method takes the sine*cos function of calculated turbulence, creating a skiny intensity pattern. With normalize box unchecked, more noisy and unregular effect can be obtained.

Woodrings method creates patterns similar to wood rings. With normalize box unchecked, more noisy and unregular effect can be obtained.

Applying Noise
If you want to apply Noise on whole image, after choosing the method, mode and amount of bit shifting, simply press Image button. Noise will be applied to whole image.

You can apply Noise through brush movement, contour and mask as well. For shape selection and brush movement refer to shapes and brushes section.

NOTE:
Resultant image is affected by all previously set
global parameters.