Joe's Filters: Joe's Threshold and Posterize

The Joe's Threshold and Posterize plugin is a part of Joe's Filters, shareware utility and image processing effects for Final Cut Pro.

What it does

Joe's Threshold and Posterize offers an extended set of thresholding controls for Final Cut Pro. A basic Threshold filter defines the breaking point between black and white, this filter adds the ability to set a number of steps (posterization) between the extremes. Basic desaturation controls can desaturate the image to result in a black and white or color posterized image. Additionally, the filter can pre and post blur the filtered image to soften edges and extend the filter's usefulness.

Example Images

Original Image
No Desaturation, Threshold 103 2 levels, no pre-blur, no post-blur	Desaturate to Green, Threshold 131 2 levels, no pre-blur, no post-blur
Desaturate to Green, Threshold 90 232 levels, no pre-blur, no post-blur	No Desaturation, Threshold 91 156 levels, pre-blur 5, post-blur 1

Applying a two-step threshold to a color image usually results in 6 colors plus black and white. This happens because the threshold applies to each color channel. Two values of Red, Green and Blue mix together to produce all of the primary and secondary colors and white (when all channels are full strength) and black (when all channels are completely off). Desaturating an image before thresholding will result in a black and white image.

Thresholding by it's nature produces hard edges which don't translate well to video. Adding a post-blur can help soften the image and reduce edge-crawl and other video artifacts that result from sharp, high-contrast edges.

The Controls

• Desaturate (No, Gray, Red, Green, Blue)

  Sets the source image to full color, or any of the four desaturation choices.

• Threshold (1 - 255)

  Sets the pixel value point at which to split the image into black and white.

• Steps (2 - 255)

  Sets the number of steps between black and white. The value is split evenly around the threshold point (for more control over this sort of thing, see Joe's Levels). This effect is often called posterization.

• Pre Blur (0 - 150)

  Applies a blur to the image before thresholding. This can help to smooth out extra detail and will round off corners.

• Post Blur (0 - 150)

  Applies a blur to the image as the last step after thresholding. To anti-alias edges and reduce edge-crawl, use a value below 1. To access decimal amounts in Final Cut Pro sliders, hold down the shift key while dragging.