ColorHalfTone method (ILEADRasterProcess)

Syntax	short ColorHalfTone(ILEADRaster * pRaster, long lMaxRad, long lCyanAngle, long lMagentaAngle, long lYellowAngle, long lBlackAngle);
Overview	Refer to Examining and Altering Bitmaps.

Remarks

(Raster Pro and above only) Creates an enlarged halftone screen for each image channel.

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 ColorHalfTone using the following values:

Parameter	Value
lMaxRad	8
lCyanAngle	108
lMagentaAngle	163
lYellowAngle	90
lBlackAngle	45

The following figure results:

$image\ColorHalfToned.gif$

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.

See Also

Elements:

GrayScale method, GrayScaleExt method, AutoColorLevel method, ColorLevel method, Correlation method, GrayScaleToDuotone method, GrayScaleToMultitone method, HolesRemovalBitmapRgn method, SelectiveColor method, Skeleton method, HalfTone method, ColorSeparate method, ColorMerge method, Desaturate method, HalfTonePattern 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.