L_ColorHalfToneBitmap

Summary

Creates an enlarged halftone screen for each image channel.

Syntax

L_LTIMGEFX_API L_INT L_ColorHalfToneBitmap(pBitmap, uMaxRad, nCyanAngle, nMagentaAngle, nYellowAngle, nBlackAngle, uFlags)

Parameters

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle referencing the bitmap to be changed.

L_UINT uMaxRad

Maximum dot (i.e. circle) size, in pixels. This value should not be less than 5.

L_INT nCyanAngle

Cyan screen angle in hundredths of degrees (+/-). A positive value will rotate the screen clockwise, while a negative value will rotate the screen counter-clockwise. Valid values are from 36000 to + 36000.

L_INT nMagentaAngle

Magenta screen angle in hundredths of degrees (+/-). A positive value will rotate the screen clockwise, while a negative value will rotate the screen counter-clockwise. Valid values are from 36000 to + 36000.

L_INT nYellowAngle

Yellow screen angle in hundredths of degrees (+/-). A positive value will rotate the screen clockwise, while a negative value will rotate the screen counter-clockwise. Valid values are from 36000 to + 36000.

L_INT nBlackAngle

Black screen angle in hundredths of degrees (+/-). A positive value will rotate the screen clockwise, while a negative value will rotate the screen counter-clockwise. Valid values are from 36000 to + 36000.

L_UINT32 uFlags

Reserved for future use. Must be 0.

Returns

Comments

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.

The filter divides the image into rectangles and replaces each rectangle with circles. Each channel has a separate grid of circles, and has its own angle setting. The size of each circle is proportional to the brightness of the rectangle that it is replacing.

This filter is named after the colored print process of color halftoning, where individual separations are made for each color: Cyan, Magenta, Yellow, and Black. The four separations are combined to make the final print. To prevent moir patterns, each separation uses a different screen angle when they are combined. In the true print process the circles are not large enough to be seen without magnification.

For an example, click here

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

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.

If the bitmap has a region, this function works only on the region. If the bitmap does not have a region, this function works on the entire bitmap.

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.

View additional platform support for this Color Halftone function.

Required DLLs and Libraries

• LTIMGEFX
• 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_DefaultDithering
• L_GrayScaleBitmap
• L_GrayScaleBitmapExt
• L_AutoColorLevelBitmap
• L_ColorLevelBitmap
• L_CorrelationBitmap
• L_GrayScaleToDuotone
• L_GrayScaleToMultitone
• L_HolesRemovalBitmapRgn
• L_SelectiveColorBitmap
• L_SkeletonBitmap
• L_HalfToneBitmap
• L_ColorSeparateBitmap
• L_ColorMergeBitmap
• L_DesaturateBitmap
• L_HalfTonePatternBitmap
• L_GetBitmapStatisticsInfo
• L_GetBitmapHistogram
• L_GetBitmapColorCount
• L_GetBitmapColors
• L_GetMinMaxBits
• L_GetMinMaxVal
• L_ConvertToColoredGray
• L_ColorizeGrayBitmap
• L_GetBitmapAlpha
• L_ShiftBitmapData
• L_SelectBitmapData
• L_AnnSetAutoHilightPen
• L_AnnSetAutoCursor
• L_IsGrayScaleBitmap
• L_WindowLevel
• L_WindowLevelBitmap
• L_WindowLevelFillLUT

Topics

• Raster Image Functions: Doing Color Expansion or Reduction
• Correcting Colors
• Raster Image Functions: Correcting Colors

Example

The following example loads a bitmap and applies the color halftone filter to it

L_INT ColorHalfToneBitmapExample(L_VOID) 
{ 
   L_INT nRet; 
   BITMAPHANDLE LeadBitmap; 
 
   /* Load the bitmap, keeping the bits per pixel of the file */ 
   nRet = L_LoadBitmap(MAKE_IMAGE_PATH(TEXT("Sample1.CMP")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   /*Apply the filter*/ 
   nRet = L_ColorHalfToneBitmap(&LeadBitmap, 15, 10800, 16200, 9000, 4500, 0); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("Result.BMP")), &LeadBitmap, FILE_BMP, 24, 0, NULL); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   //free bitmap 
   if (LeadBitmap.Flags.Allocated) 
      L_FreeBitmap(&LeadBitmap); 
 
   return SUCCESS; 
}