HalfTonePattern method (ILEADRasterProcess)

Syntax	short HalfTonePattern(ILEADRaster * pRaster, long lContrast, long lRipple, long lAngleContrast, long lAngleRipple, long lAngleOffset, OLE_COLOR crForeGround, OLE_COLOR crBackGround, HalfTonePatterenConstants Flags);
Overview	Refer to Examining and Altering Bitmaps.

Remarks

(Raster Pro and above only) Creates a halftone screen effect for an image while keeping its continuous range of tones.

Use this method to create a halftone screen effect for an image while keeping its continuous range of tones. Use the lContrast parameter to control the amount of the midtones in the image.

Use the ColorHalfTone to create an enlarged halftone screen for each image channel. The filter divides the image into rectangles and replaces each rectangle with circles, one for each channel. The size of each circle is proportional to the brightness of the rectangle, which it is replacing.

Use the HalfTone method to convert a 1-, 4-, 8-, 16-, 24-, or 32-bit bitmap to a halftoned bitmap, with a specified pattern rotation. A halftoned bitmap is a 1-bit bitmap that has been dithered for black and white printing or display.

Use the GrayScaleExt method to convert any bitmap to a gray scale bitmap without changing its resolution.

As an example, if you use the following image:

$image\diffuseglowbefore.gif$

And you were to call the HalfTonePattern method using the following settings:

Parameter	Value
lContrast	1
lRipple	20000
lAngleContrast	na
lAngleRipple	na
lAngleOffset	na
crForeGround	Black
crBackGround	White
Flags	HTPATTERN_DOT

The following figure results:

$image\halftonepatterndot.gif$

As another example, if you were to use the same original bitmap but call HalfTonePattern using the following settings:

Parameter	Value
lContrast	75
lRipple	20000
lAngleContrast	85
lAngleRipple	4
lAngleOffset	54
crForeGround	White
crBackGround	Brown
Flags	HTPATTERN_CIRCLE

The following figure results:

$image\halftonepatterncircle.gif$

This method 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 method works only on the region. If the bitmap does not have a region, this method works on the entire bitmap.

This method 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 method.

Elements:	GrayScale method, GrayScaleExt method, AutoColorLevel method, ColorLevel method, Correlation method, GrayScaleToDuotone method, GrayScaleToMultitone method, HolesRemovalBitmapRgn method, SelectiveColor method, Skeleton method, HalfTone method, Pointillist method, ColorHalfTone method, ColorSeparate method, ColorMerge method, Desaturate method, GetBitmapStatisticsInfo method, GetHistogram method, GetColorCount method, GetMinMaxBits method, GetMinMaxVal method, ConvertToColoredGray method, ColorizeGray method, BitmapAlpha property, ShiftData method, SelectData method, GetHistogramGray method, IsGrayScale property, WindowLevel method, WindowLevelFillLUT method
Topics:	Raster Images: Doing Color Expansion or Reduction.
	Raster Images: Filtering Images