L_ColorHalfToneBitmap

#include "l_bitmap.h"

L_INT EXT_FUNCTION L_ColorHalfToneBitmap(pBitmap, uMaxRad, nCyanAngle, nMagentaAngle, nYellowAngle, nBlackAngle)

pBITMAPHANDLE pBitmap;	/* pointer to the bitmap handle */
L_UINT uMaxRad;	/* maximum dot size */
L_INT nCyanAngle;	/* cyan screen angle */
L_INT nMagentaAngle;	/* magenta screen angle */
L_INT nYellowAngle;	/* yellow screen angle */
L_INT nBlackAngle;	/* black screen angle */

Creates an enlarged halftone screen for each image channel. This function is available only in the Document/Medical Toolkits.

Parameter	Description
pBitmap	Pointer to the bitmap handle referencing the bitmap to be changed.
uMaxRad	Maximum dot (i.e. circle) size, in pixels. This value should not be less than 5.
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.
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.
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.
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.

Returns

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

Comments

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 moiré 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.

As an example, if you use the following figure:

$image\Rafting.gif$

and you call L_ColorHalfToneBitmap using the following values:

Parameter	Value
uMaxRad	8
nCyanAngle	108
nMagentaAngle	163
nYellowAngle	90
nBlackAngle	45

The following figure results:

$image\ColorHalfToned.gif$

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 only in the Document/Medical 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 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_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_GetBitmapHistogramGray, 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*/

BITMAPHANDLE LeadBitmap;
/* Load the bitmap, keeping the bits per pixel of the file */
L_LoadBitmap(TEXT("Sample1.CMP"), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL);
/*Apply the filter*/
L_ColorHalfToneBitmap(&LeadBitmap, 15, 10800, 16200, 9000,4500);