L_ShiftZeroToNegative

Summary

Converts an unsigned bitmap to a signed bitmap by decreasing intensity values by a specific amount.

Syntax

L_LTIMGCOR_API L_INT L_ShiftZeroToNegative(pBitmap, nShiftAmount, nMinInput, nMaxInput, nMinOutput, nMaxOutput, uFlags)

Parameters

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle referencing the bitmap to convert.

L_INT nShiftAmount

The amount by which to decrease the bitmap's intensity values.The amount that is used to shift the bitmap data to the negative side.

L_INT nMinInput

The bitmap's minimum intensity value. This value can be obtained by calling the L_GetMinMaxVal function.

L_INT nMaxInput

The bitmap's maximum intensity value. This value can be obtained by calling the L_GetMinMaxVal function.

L_INT nMinOutput

The minimum intensity value allowed in the resulting image. If this function results in an intensity value less than this value, the intensity value in the resulting image will be set to this minimum value.

L_INT nMaxOutput

The maximum intensity value allowed in the resulting image. If this function results in an intensity value more than this value, the intensity value in the resulting image will be set to this maximum value.

L_UINT32 uFlags

Reserved for future use. Must be 0.

Returns

Comments

By decreasing the intensity values of the bitmap (creating some negative values), a value of zero in the original bitmap would be shifted to a value of nShiftAmount.

This function is similar to L_ConvertBitmapUnsignedToSigned. However, L_ShiftZeroToNegative lets the user determine the value by which to shift the data, while in L_ConvertBitmapUnsignedToSigned, the shift is fixed always. (i.e. shift center to zero.)

This function is used usually after the function L_ShiftMinimumToZero.

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 does not 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 in the Document and Medical Imaging toolkits.

This function does not support 32-bit grayscale images. It returns the error code ERROR_GRAY32_UNSUPPORTED if a 32-bit grayscale image is passed to this function.

Required DLLs and Libraries

• LTIMGCOR
• 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

Win32, x64, Linux.

See Also

Functions

• L_ClearNegativePixels
• L_ConvertBitmapUnsignedToSigned
• L_ConvertBitmapSignedToUnsigned
• L_ShiftMinimumToZero

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 ShiftZeroToNegativeExample(L_VOID) 
{ 
   L_UINT nShiftAmount; 
   BITMAPHANDLE   LeadBitmap; 
   L_INT nRet; 
   LOADFILEOPTION LoadFileOption; 
 
   /* enable negative pixels to be loaded from TIFF files */ 
   nRet = L_GetDefaultLoadFileOption(&LoadFileOption, sizeof(LOADFILEOPTION)); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   LoadFileOption.Flags |= ELO_SIGNED; 
 
   /* Load the bitmap, keeping the bits per pixel of the file */ 
   nRet = L_LoadBitmap(MAKE_IMAGE_PATH(TEXT("Beauty16.jpg")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGRORGRAY, &LoadFileOption, NULL); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   // Convert the bitmap to unsigned bitmap by shifting the negative values to become positive.  
   nRet = L_ShiftMinimumToZero(&LeadBitmap, &nShiftAmount, 0); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   // Apply multiscale enhancement 
   nRet = L_MultiScaleEnhancementBitmap(&LeadBitmap, 2000, 4, MSE_DEFAULT, 0, 0, MSE_GAUSSIAN | MSE_EDGEENH); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   // Convert the bitmap back to signed by shifting the same amount in the negative side. 
   nRet = L_ShiftZeroToNegative(&LeadBitmap, nShiftAmount, -32767, 32766, 0, 65535, 0); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   //free Bitmap 
   if (LeadBitmap.Flags.Allocated) 
      L_FreeBitmap(&LeadBitmap); 
 
   return SUCCESS; 
}