L_ShiftMinimumToZero

#include "l_bitmap.h"

L_INT EXT_FUNCTION L_ShiftMinimumToZero(pBitmap, puShiftAmount)

pBITMAPHANDLE pBitmap;	/* pointer to the bitmap handle */
L_UINT L_FAR * puShiftAmount;	/* pointer to the shifting amount */

Converts the signed bitmap to an unsigned bitmap by increasing/shifting the bitmap's intensity values, so the lowest intensity value (the most negative value) will be shifted to zero. This function is available in the Raster Pro and above toolkits.

Parameter	Description
pBitmap	Pointer to the bitmap handle referencing the bitmap to convert.
puShiftAmount	Pointer to a variable to be updated with the value by which the intensity values were shifted.

Returns

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

Comments

This function is similar to L_ConvertBitmapSignedToUnsigned. However, L_ShiftMinimumToZero updates the puShiftAmount parameter with the value by which the intensity values were shifted.

The L_ShiftMinimumToZero and L_ShiftZeroToNegative are most often used in concert with one or more image processing or analysis functions. L_ShiftMinimumToZero converts signed data to unsigned data, in preparation for some image processing or analysis. (Most image processing functions work only on unsigned data.) After the image processing or analysis is performed, L_ShiftZeroToNegative converts the unsigned data back to signed data.

This function updates the pBitmap->Flags.Signed, MinVal and MaxVal members of the BITMAPHANDLE.

This function doesn’t support 8-bit images.

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.

This function supports signed data images.

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_ClearNegativePixels, L_ConvertBitmapUnsignedToSigned, L_ConvertBitmapSignedToUnsigned, L_ShiftZeroToNegative
Topics:	Raster Image Functions: Getting and Setting Pixel Values
	Processing an Image

Example

// This function will apply L_MultiScaleEnhancementBitmap on a signed image,
// but since L_MultiScaleEnhancementBitmap doesn’t support signed images,
// we will convert the image to unsigned image, apply the effect,
// and then convert it back to signed image.

   L_INT nShiftAmount;
   BITMAPHANDLE LeadBitmap;
   L_INT nRet;
   LOADFILEOPTION LoadFileOption;

   /* enable negative pixels to be loaded from TIFF files */
   L_GetDefaultLoadFileOption (&LoadFileOption, sizeof(LOADFILEOPTION));
   LoadFileOption.Flags |= ELO_SIGNED;

   /* Load the bitmap, keeping the bits per pixel of the file */
   L_LoadBitmap (TEXT("IMAGE1.TIF"), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGRORGRAY, &LoadFileOption, NULL);

// Convert the bitmap to unsigned bitmap by shifting the negative values to become positive.
   nRet = L_ShiftMinimumToZero(&LeadBitmap, &nShiftAmount);

   // Apply multiscale enhancement
   L_MultiScaleEnhancementBitmap (&LeadBitmap, 2000, 4, MSE_DEFAULT , 0, 0, MSE_GAUSSIAN | MSE_EDGEENH);

// Convert the bitmap back to signed by shifting the same amount in the negative side.
   nRet = L_ShiftZeroToNegative(&LeadBitmap, nShiftAmount, -32767, 32766, 0, 65535);