Type Default Value Read Only Description
String   "Spot,30,100,CosineDot" No The default halftone type and options.




Specifies the default halftone type and options.

The default halftone remains in effect until an embedded halftone screen is encountered.

The Type can be:

  • Spot
  • ErrorDiffusion
  • OrderedDither

If the type is Spot, then an angle in degrees, frequency and spot function can also be specified. These should be separated by commas with no extraneous spaces. The spot functions available are:

  • SimpleDot
  • InvertedSimpleDot
  • DoubleDot
  • InvertedDoubleDot
  • CosineDot
  • Double
  • InvertedDouble
  • Line
  • LineX
  • LineY
  • Round
  • Ellipse
  • EllipseA
  • InvertedEllipseA
  • EllipseB
  • EllipseC
  • InvertedEllipseC
  • Square
  • Cross
  • Rhomboid
  • Diamond

For full details of how Halftones work, you should see the Adobe PDF Specification available from the Adobe web site.




The following example shows the effect that this parameter has on PDF rendering.

Set theDoc = Server.CreateObject("ABCpdf10.Doc")
Set image = Server.CreateObject("ABCpdf10.Image")
image.SetFile "c:\mypics\Shuttle.jpg"
theDoc.Rect.String = image.Selection.String
' Save rendered image as black and white picture using Line spot function
theDoc.Rendering.UseEmbeddedHalftone = False
theDoc.Rendering.DotsPerInch = 50
theDoc.Rendering.ColorSpace = "Gray"
theDoc.Rendering.BitsPerChannel = 1
theDoc.Rendering.DefaultHalftone = "Spot,30,100,Line"
theDoc.Rendering.Save "c:\mypdfs\RenderingHalftoneLine.png"
' Save rendered image as black and white picture using Diamond spot function
theDoc.Rendering.DefaultHalftone = "Spot,0,100,Diamond"
theDoc.Rendering.Save "c:\mypdfs\RenderingHalftoneDiamond.png"