Acorn Acorn 6

Blur Filters

Many of the filter definitions below come directly from Apple’s core image filter reference.  

Background Blur:  Blurs the background using the input image as a mask.  This filter requires at least one layer below it to work.  See video tutorial:  Background Blur Filter.



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Box Blur

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Disc Blur

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Gaussian Blur

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Motion Blur

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Zoom Blur

Box Blur:  Blurs an image using a box-shaped convolution kernel.  Use a slider control to modify the radius of blur.

Disc Blur:  Blurs an image using a disc-shaped convolution kernel.  Use a slider control to modify the radius of blur.

Gaussian Blur:  Spreads source pixels by an amount specified by a Gaussian distribution. Use a slider control to modify the radius of blur.  A drop down menu offers the option to ‘clamp’ to prevent transparent pixels from outside your layer entering the blur.  

Linear Gradient Blur:  Applies a blur across your image with on-canvas controls similar to applying a gradient.

Masked Variable Blur:  Blurs the source image according to the brightness levels in a mask image.  Shades of gray in the mask image vary the blur radius from zero (where the mask image is black) to the radius specified in the radius field (where the mask image is white).  Drag and drop an image into the mask field.  

Motion Blur:  Blurs an image to simulate the effect of using a camera that moves a specified angle and distance while capturing the image.

Zoom Blur:  Simulates the effect of zooming the camera while capturing the image.  

Median Filter:  Computes the median value for a group of neighboring pixels and replaces each pixel value with the median.  The effect is to reduce noise.  There are no parameters to adjust.



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Median Filter

Noise Reduction:  Reduces noise using a threshold value to define what is considered noise.  Small changes in luminance below that value are considered noise and get a noise reduction treatment, which is a local blur.  Changes above the threshold value are considered edges, so they are sharpened.  



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Sharpness increased

Radial Gradient Blur: Creates a radial blur similar to a vignette effect.

filters examples.jpg   

radial gradient blur.acorn

Try playing around with some of the filters and experiment, experiment, experiment.  For more information, check out the Tutorials or send an email to and request a tutorial.

Additional Relevant Documentation  

Filters Basics (video tutorial)

Filters Basics