highpass_imagehighpass_imageHighpassImageHighpassImagehighpass_image (Operator)

Name

highpass_imagehighpass_imageHighpassImageHighpassImagehighpass_image — Extract high frequency components from an image.

Signature

highpass_image(Image : Highpass : Width, Height : )

Description

highpass_imagehighpass_imageHighpassImageHighpassImageHighpassImagehighpass_image extracts high frequency components in an image by applying a linear filter with the following matrix (in case of a 7x5 matrix): 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 -35 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 This corresponds to applying a mean operator (mean_imagemean_imageMeanImageMeanImageMeanImagemean_image), and then subtracting the original gray value. For byte images, a value of 128 is added to the result, i.e., zero crossings occur for 128. Correspondingly for uint2 images, 32767 is added.

This filter emphasizes high frequency components (edges and corners). The cutoff frequency is determined by the size (Height x Width) of the filter matrix: the larger the matrix, the smaller the cutoff frequency is.

At the image borders the pixels' gray values are mirrored. In case of over- or underflow the gray values are clipped (255 and 0, resp.).

Attention

If even values are passed for HeightHeightHeightHeightheightheight or WidthWidthWidthWidthwidthwidth, the operator uses the next larger odd value instead. Thus, the center of the filter mask is always uniquely determined.

highpass_imagehighpass_imageHighpassImageHighpassImageHighpassImagehighpass_image can be executed on OpenCL devices. The same limitations as for mean_imagemean_imageMeanImageMeanImageMeanImagemean_image and sub_imagesub_imageSubImageSubImageSubImagesub_image apply.

Note that filter operators may return unexpected results if an image with a reduced domain is used as input. Please refer to the chapter Filters.

Execution Information

Supports OpenCL compute devices.
Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Automatically parallelized on tuple level.
Automatically parallelized on channel level.
Automatically parallelized on domain level.

Parameters

ImageImageImageImageimageimage (input_object) (multichannel-)image(-array) → object (byte* / uint2*) *allowed for compute devices

Input image.

HighpassHighpassHighpassHighpasshighpasshighpass (output_object) (multichannel-)image(-array) → object (byte / uint2)

High-pass-filtered result image.

WidthWidthWidthWidthwidthwidth (input_control) extent.x → (integer)

Width of the filter mask.

Default value: 9

Suggested values: 3, 5, 7, 9, 11, 13, 17, 21, 29, 41, 51, 73, 101

Typical range of values: 3 ≤ Width Width Width Width width width ≤ 501

Minimum increment: 2

Recommended increment: 2

Restriction: Width >= 3 && odd(Width)

HeightHeightHeightHeightheightheight (input_control) extent.y → (integer)

Height of the filter mask.

Default value: 9

Suggested values: 3, 5, 7, 9, 11, 13, 17, 21, 29, 41, 51, 73, 101

Typical range of values: 3 ≤ Height Height Height Height height height ≤ 501

Minimum increment: 2

Recommended increment: 2

Restriction: Height >= 3 && odd(Height)

Example (C)

highpass_image(Image,&Highpass,7,5);
threshold(Highpass,&Region,60.0,255.0);
skeleton(Region,&Skeleton);

Result

highpass_imagehighpass_imageHighpassImageHighpassImageHighpassImagehighpass_image returns 2 (H_MSG_TRUE) if all parameters are correct. If the input is empty the behavior can be set via set_system('no_object_result',<Result>)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)set_system("no_object_result",<Result>). If necessary, an exception is raised.

Possible Successors

thresholdthresholdThresholdThresholdThresholdthreshold, skeletonskeletonSkeletonSkeletonSkeletonskeleton

Alternatives

mean_imagemean_imageMeanImageMeanImageMeanImagemean_image, sub_imagesub_imageSubImageSubImageSubImagesub_image, convol_imageconvol_imageConvolImageConvolImageConvolImageconvol_image, bandpass_imagebandpass_imageBandpassImageBandpassImageBandpassImagebandpass_image

Module

Foundation

Operators