ImageGear for C and C++ on Linux v20.0 - Updated
API Reference Guide > Core Component API Reference > Core Component Functions Reference > Image Processing Functions > IG_IP_NR_ROI_to_HIGEAR_mask

This function is a non-rectangular ROI (region on interest) support function whose purpose is to build a non-rectangular ROI mask from a set of segment descriptors that you pass in, and to return a pointer to a non-rectangular ROI mask data structure.


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        AT_MODE nSimpleAreaTypeID, 
        LPVOID lpAreaSegmentDesc,


Name Type Description
nSimpleAreaTypeID AT_MODE Set to an AT_MODE constant that describes what kind of non-rectangular region of interest (ROI) you will be passing in. See supported AT_MODE constants below.
lpAreaSegmentDesc LPVOID Pass in an array of segment descriptors which will be used to reproduce/render the non-rectangular ROI as a mask. These segment descriptors can be points in the case of polygons, points and angles in the case of ellipses and so on. The segment descriptors use image coordinates to describe the mask.
lpNR_ROI LPAT_NR_ROI_MASK ImageGear returns you a structure of type AT_NR_ROI_MASK which contains the HIGEAR handle of the new mask HIGEAR and the "reference point" for its placement within HIGEAR.

Return Value:

Returns the number of ImageGear errors that occurred during this function call. If there are no errors, the return value is IGE_SUCCESS.

Supported Raster Image Formats:

This function does not process image pixels.


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AT_ERRCOUNT       nErrcount;
AT_NR_ROI_MASK   region;
AT_POINT        ROI[];
nErrcount = 
        IG_IP_NR_ROI_to_HIGEAR_mask(IG_ROI_IS_POLYGON, &ROI[0], &region);


This non-rectangular ROI mask data structure (of type AT_NR_ROI_MASK) is then used in conjunction with other API functions to create, associate, modify, and apply the non-rectangular ROI to the source image.

The AT_NR_ROI_MASK structure, shown below, contains two important pieces of information. ptMaskOffset describes the coordinates for reference point for the mask HIGEAR. ptMaskOffset is the (x,y) position in the original HIGEAR at which the upper left corner of the mask HIGEAR should be placed. The mask HIGEAR is actually a rectangle which is calculated by determining the smallest rectangular area that can encompass the entire non-rectangular ROI. We refer to this area as the "bounding rectangle". Within the mask, which represents the bounding rectangle, a pixel value of 1 indicates that the pixel is within the non-rectangular ROI; a pixel value of 0 indicates that the pixel is outside the non-rectangular ROI.

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typedef struct tag     AT_NR_ROI_MASK
        AT_POINT ptMaskOffet;
        HIGEAR hMask;

The second member of the mask structure is a HIGEAR handle to the actual mask image. The mask HIGEAR is a run length-encoded binary image.

You must also pass this function an argument that specifies whether the region of interest is elliptical, polygonal, or rectangular (the default), using one of the following constants:

The default ROI type, which is IG_ROI_IS_RECTANGLE means that when this mask is associated with and activated for an image, all affected API should use the AT_RECT argument that is part of their argument list. If nSimpleAreaTypeID is set to IG_ROI_IS_ELLIPSE or IG_ROI_IS_POLYGON, all affected API will override their AT_RECT arguments and instead look for an associated AT_NR_ROI_MASK.

The lpNR_ROI parameter will store the mask HIGEAR information structure when the function return value is IGE_SUCCESS. 

Use IG_IP_NR_ROI_mask_associate() function to associate the mask HIGEAR with a HIGEAR image.
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