6.7. Sparkle

6.7.1. Overview

Figure 17.129. Applying example for the Sparkle filter

Original image

Filter “Sparkle” applied

This filter adds sparkles to your image. It uses the lightest points according to a threshold you have determined. It is difficult to foresee where sparkles will appear. But you can put white points on your image where you want sparkles to be.

6.7.2. Activate the filter

This filter is found in the image window menu under Filters → Light and Shadow → Sparkle….

6.7.3. Parameter Settings

Figure 17.130. “Sparkle” filter options

Sliders and input boxes allow you to set values.

Preview

If checked, parameter setting results are interactively displayed in preview. Scroll bars allow you to move around the image.

Luminosity threshold

The higher the threshold, the more areas are concerned by sparkling (0.0-0.1).

Flare intensity

When this value increases, the central spot and rays widen (0.0-1.0).

Spike length

This is ray length (1-100). When you reduce it, small spikes decrease first.

Spike points

Number of starting points for spikes (0-16). It’s the number of big spikes. There is the same number of small spikes. When number is odd, small spikes are opposite the big ones. When number is even, big spikes are opposite another big spike.

Spike angle

This is angle of first big spike with horizontal (-1 +360). -1 determines this value at random. If a spot has several pixels within required threshold, each of them will generate a sparkle. If angle is positive, they will all be superimposed. With -1, each sparkle will have a random rotation resulting in numerous thin spikes.

Spike density

This option determines the number of sparkles on your image. It indicates the percentage (0.0-1.0) of all possible sparkles that will be preserved.

Transparency

When you increase transparency (0.0-1.0), sparkles become more transparent and the layer beneath becomes visible. If there is no other layer, sparkle saturation decreases.

Random hue

This option should change sparkle hue at random… (0.0-1.0).

Random saturation

This option should change sparkle saturation at random… (0.0-1.0).

Preserve luminosity

Gives to all central pixels the luminosity of the brightest pixel, resulting in increasing the whole sparkle luminosity.

Inverse

Instead of selecting brightest pixels in image, Sparkle will select the darkest ones, resulting in dark sparkles.

Add border

Instead of creating sparkles on brightest pixels, this option creates an image border made up of numerous sparkles.

Natural color, Foreground color, Background color

You can change there the color of central pixels. This color will be added in Screen mode (Multiply if Inverse is checked). “Natural color” is the color of the pixel in the image.