# highpassfilter¶

Syntax: highpassfilter(input image, output image, spatial sigma, shift, boundary condition, allow optimization)

Gaussian high-pass filtering. Use to remove smooth, large-scale gray-scale variations from the image.

Subtracts a Gaussian filtered version of input from itself. If optimization flag is set to true, processes integer images with more than 8 bits of resolution with separable convolution and floating point images with FFT filtering. If optimization flag is set to false, processes all integer images with normal convolution and floating point images with separable convolution.

This command can be used in the distributed processing mode. Use distribute command to change processing mode from local to distributed.

## Arguments¶

### input image [input]¶

Data type: uint8 image, uint16 image, uint32 image, uint64 image, int8 image, int16 image, int32 image, int64 image, float32 image

Input image.

### output image [output]¶

Data type: uint8 image, uint16 image, uint32 image, uint64 image, int8 image, int16 image, int32 image, int64 image, float32 image

Output image.

### spatial sigma [input]¶

Data type: 3-component real vector

Standard deviation of Gaussian kernel.

### shift [input]¶

Data type: real

Default value: 0

Constant to be added to the pixel values. Use to set the mean of the filtered image to a desired value. Useful especially when filtering unsigned images where non-shifted highpass filtering will lead to negative values that will be clipped to zero.

### boundary condition [input]¶

Data type: boundary condition

Default value: Nearest

Type of boundary condition. Zero indicates that values outside of image bounds are taken to be zero. Nearest indicates that the nearest value inside the image is to be used in place of values outside of image bounds.

### allow optimization [input]¶

Data type: boolean

Default value: True

Set to true to allow optimized processing of images with high dynamic range data types. Might cause small deviations from true filtration result, and edge artefacts.