L_HighPassFilterBitmap

#include "l_bitmap.h"

L_INT EXT_FUNCTION L_HighPassFilterBitmap(pBitmap, uRadius, uOpacity)

pBITMAPHANDLE pBitmap;	/* pointer to the bitmap handle */
L_UINT uRadius;	/* radius of the neighborhood */
L_UINT uOpacity;	/* opacity */

Removes low frequency details in a bitmap, resulting in a sharpened image. This function is available in the Raster Pro and above toolkits.

Parameter	Description
pBitmap	Pointer to the bitmap handle that references the bitmap to which to apply the filter.
uRadius	Value greater than 0 that indicates the radius of the neighborhood on which the filter is applied, in pixels.
uOpacity	Value that represents the intensity of the effect. The valid range is from 0 to 100. At 100, only the object outlines remain.

Returns

SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

This filter removes low-frequency detail in the bitmap. The effect is opposite to that of the Gaussian Blur filter (L_GaussianFilterBitmap).

To increase the thickness of the edges, increase the value of uRadius. Usually a low value for uRadius is better.

Unlike the L_UnsharpMaskBitmap function, when using this function image noise is not increased.

As an example, if you use the following image:

$image\highpassfilterBefore.gif$

And you were to call L_HighPassFilterBitmap using the following settings:

Parameter	Value
uRadius	6
uOpacity	100

The following figure results:

$image\highpassfilter.gif$

If the bitmap has a region, the effect will be applied on the region only.

This function supports 12- and 16-bit grayscale and 48- and 64-bit color images. Support for 12- and 16-bit grayscale and 48- and 64-bit color images is available only in the Document/Medical toolkits.

To update a status bar or detect a user interrupt during execution of this function, refer to L_SetStatusCallback.

This function does not support signed data images. It returns the error code ERROR_SIGNED_DATA_NOT_SUPPORTED if a signed data image is passed to this function.

Required DLLs and Libraries

LTIMG

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Platforms

Windows 95 / 98 / Me, Windows 2000 / XP.

See Also

Functions:	L_SharpenBitmap, L_PosterizeBitmap, L_MosaicBitmap, L_EmbossBitmap, L_MedianFilterBitmap, L_AddBitmapNoise, L_IntensityDetectBitmap, L_SpatialFilterBitmap, L_BinaryFilterBitmap, L_SolarizeBitmap, L_WindowLevel, L_UnsharpMaskBitmap, L_GaussianFilterBitmap
Topics:	Raster Image Functions: Filtering Images
	Removing Noise
	Detecting and Enhancing Edges and Lines
	Raster Image Functions: Detecting and Enhancing Edges and Lines

Example

BITMAPHANDLE LeadBitmap; /* Bitmap handle for the image */

/* Load a bitmap at its own bits per pixel */
L_LoadBitmap (TEXT("IMAGE3.CMP"), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL);

/*Sharpen image by applying the high pass filter*/
L_HighPassFilterBitmap(&LeadBitmap, 10, 100);