Function:ImageFilter

Linear filters are an important part of Image Processing Applications. CUVI provides a single generic filter function to apply any filter of any size to an image. We have in-build flags for various famous filters and programmer can input his custom filter elements as well.

Function

CuviStatus imageFilter(CuviImage* srcImage, CuviImage* dstImage, CuviROI roi, CuviFilter* filter, CuviStream* stream = NULL);

Parameters

Name	Type	Description
srcImage	CuviImage*	Input Image
dstImage	CuviImage*	Output Image
roi	CuviROI	Region of Interest
filter	CuviFilter*	This structure contains filter parameters including dimensions of the filter kernel, coefficients and anchor position
stream	CuviStream*	GPU stream ID for execution

Image Type Support

Input	Output
8uC1	8uC1
8uC3	8uC3
16uC1	16uC1
16uC3	16uC3
32fC1	32fC1
32fC3	32fC3
8uC1	32fC1
8uC3	32fC3
16uC1	32fC1
16uC3	32fC3

Anchor Position

For creating custom square or rectangular filter kernel, you need to specify the taps as 1D row-major 32bit floating-point array. By default, the center of the 2D filter kernelis placed on the image pixel that corresponds to the current output location. This is known as the filter kernel anchor and it’s position is given by a 2D point. For a 3x3 filter kernel, the default anchor position is -1,-1 which corresponds to the center of the filter kernel, -2,-2 for 5x5 filter and so on. You can change this to another location within the filter kernel through the anchorPositionargument of the imFilter function. Here’s how you create a custom filter kernel and populate it with taps:

Sample

Input	Average 5x5	Gaussian 5x5 with sigma=0.35	Unsharp with alpha=0.2
Input	X Derivative	Y Derivative

Example

//Input image CuviImage* gimg = new CuviImage(cuviSize(img->width,img->height),img->depth,img->nChannels); gimg->upload(img->imageData,img->widthStep); //Output Image CuviImage* gout = new CuviImage(cuviSize(img->width,img->height),img->depth,img->nChannels); //Choosing ROI CuviROI roi = cuviROI(0,0,img->width,img->height); //Creating a 5x5 Averaging Filter. User can also enter custom coefficients CuviFilter* f; cuviCreateFilter(&f,5,5); cuviCreateFilterSpecial(f,CUVI_FILTER_AVERAGE); //Applying filter 'f' on the image cuvi::imageFiltering::imFilter(gimg,gout,roi,f);