StartDithering Method

Initializes the buffered dithering of an image.

Syntax

Visual Basic
C#
WinRT C#
WinRT JavaScript
C++

public void StartDithering( 
   RasterColor[] palette,
   int colors
)

'Declaration
 
Public Sub StartDithering( _
   ByVal palette() As RasterColor, _
   ByVal colors As Integer _
)

'Usage
 
Dim instance As RasterImage
Dim palette() As RasterColor
Dim colors As Integer
 
instance.StartDithering(palette, colors)

public void StartDithering( 
   RasterColor[] palette,
   int colors
)

 function Leadtools.RasterImage.StartDithering( 
   palette ,
   colors 
)

public:
void StartDithering( 
   array<RasterColor>^ palette,
   int colors
)

Parameters

palette: The palette this uses for dithering. You can specify your own palette, or use a null reference (Nothing in Visual Basic) for LEAD's fixed palette.
colors: Number of colors used in the palette. If the palette contains more colors, only the first colors colors are used. Valid values are 2 to 256.

Remarks

The following flow chart shows how the methods relate to each other:

Dithering Flow Chart

The following properties from the RasterImage are used to control the dithering operation:

Width
Height
BitsPerPixel
Order - if BitsPerPixel is greater than 8
DitheringMethod - if BitsPerPixel is less than 16

This method does not support signed images.

For more information, refer to Introduction to Image Processing With LEADTOOLS.

Example

Visual Basic
C#
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Public Sub StartDitheringExample()
      Dim codecs As RasterCodecs = New RasterCodecs()
      ' Load an image that has BottomLeft ViewPerspective
      Dim image As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1.CMP"))

      Dim Palette As RasterColor() = RasterPalette.Fixed(8)

      ' Create the new palletized image.
      Dim destinationImage As RasterImage = New RasterImage(RasterMemoryFlags.Conventional, image.Width, image.Height, 8, image.Order, image.ViewPerspective, Palette, IntPtr.Zero, 0)

      ' Set the dithering method.
      image.DitheringMethod = RasterDitheringMethod.StevensonArce

      ' Initialize the dithering process.
      image.StartDithering(Palette, 256)

      ' Allocate the output buffer for 8-bit data.
      Dim InBuffer As Byte() = New Byte(image.Width * 3 - 1) {} ' Buffer to hold the input row.
      Dim OutBuffer As Byte() = New Byte(image.Width - 1) {} ' Buffer to hold the output row.

      ' Use DitherLine method to process each row in the image.
      Dim i As Integer = 0
      Do While i < image.Height
         image.GetRow(i, InBuffer, 0, image.BytesPerLine)
         image.DitherLine(InBuffer, 0, OutBuffer, 0)
         destinationImage.SetRow(i, OutBuffer, 0, destinationImage.BytesPerLine)
         i += 1
      Loop
      ' End the dithering process.
      image.StopDithering()

      codecs.Save(destinationImage, Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1_DitherLine.BMP"), RasterImageFormat.Bmp, 0)

      image.Dispose()
      destinationImage.Dispose()
      codecs.Dispose()
   End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

public void StartDitheringExample()
   {
      RasterCodecs codecs = new RasterCodecs();
      // Load an image that has BottomLeft ViewPerspective
      RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1.CMP"));

      RasterColor[] Palette = RasterPalette.Fixed(256);

      // Create the new palletized image.
      RasterImage destinationImage = new RasterImage(RasterMemoryFlags.Conventional, image.Width, image.Height, 8, image.Order, image.ViewPerspective, Palette, IntPtr.Zero, 0);

      // Set the dithering method.
      image.DitheringMethod = RasterDitheringMethod.StevensonArce;

      // Initialize the dithering process.
      image.StartDithering(Palette, 256);

      // Allocate the output buffer for 8-bit data.
      byte[] InBuffer = new byte[image.Width * 3];// Buffer to hold the input row.
      byte[] OutBuffer = new byte[image.Width];// Buffer to hold the output row.

      // Use DitherLine method to process each row in the image.
      for(int i = 0; i < image.Height; i++)
      {
         image.GetRow(i, InBuffer, 0, image.BytesPerLine);
         image.DitherLine(InBuffer, 0, OutBuffer, 0);
         destinationImage.SetRow(i, OutBuffer, 0, destinationImage.BytesPerLine);
      }
      // End the dithering process.
      image.StopDithering();

      codecs.Save(destinationImage, Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1_DitherLine.BMP"), RasterImageFormat.Bmp, 0);

      image.Dispose();
      destinationImage.Dispose();
      codecs.Dispose();
   }

static class LEAD_VARS
{
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}

RasterImageExamples.prototype.StartDitheringExample = function () {
   Tools.SetLicense();
   with (Leadtools) {
      with (Leadtools.Codecs) {
         var codecs = new RasterCodecs();

         // Load an image that has BottomLeft ViewPerspective
         var srcFileName = "Assets\\Image1.cmp";
         var image;
         var destinationImage;
         return Tools.AppInstallFolder().getFileAsync(srcFileName).then(function (loadFile) {
            return codecs.loadAsync(LeadStreamFactory.create(loadFile))
         })
            .then(function (img) {
               image = img;

               var Palette = [RasterColorHelper.create(0, 0, 0),
                  RasterColorHelper.create(255, 255, 255),
                  RasterColorHelper.create(255, 0, 0),
                  RasterColorHelper.create(0, 255, 0),
                  RasterColorHelper.create(0, 0, 255),
                  RasterColorHelper.create(255, 255, 0),
                  RasterColorHelper.create(0, 255, 255),
                  RasterColorHelper.create(255, 0, 255),
                  RasterColorHelper.create(128, 128, 0),
                  RasterColorHelper.create(0, 128, 128),
                  RasterColorHelper.create(128, 128, 128),
                  RasterColorHelper.create(128, 0, 128),
                  RasterColorHelper.create(128, 255, 128),
                  RasterColorHelper.create(128, 255, 255),
                  RasterColorHelper.create(255, 128, 128),
                  RasterColorHelper.create(255, 255, 128)
               ];

               // Create the new palletized image.
               destinationImage = new RasterImage(RasterMemoryFlags.conventional, image.width, image.height, 4, image.order, image.viewPerspective, Palette);

               // Set the dithering method.
               image.ditheringMethod = RasterDitheringMethod.stevensonArce;

               // Initialize the dithering process.
               image.startDithering(Palette, Palette.length);

               // Allocate the output buffer for 8-bit data.
               var InBuffer = new Uint8Array(image.bytesPerLine);// Buffer to hold the input row.
               var OutBuffer = new Uint8Array(destinationImage.bytesPerLine);// Buffer to hold the output row.

               // Use DitherLine method to process each row in the image.
               image.accessData();
               for (var i = 0; i < image.height; i++) {
                  image.getRow(i, InBuffer, 0, image.bytesPerLine);
                  image.ditherLine(InBuffer, OutBuffer);
                  destinationImage.setRow(i, OutBuffer, 0, destinationImage.bytesPerLine);
               }
               // End the dithering process.
               image.stopDithering();
               image.releaseData();

               return Tools.AppLocalFolder().createFileAsync("IMAGE1_DitherLine.BMP")
            })
            .then(function (saveFile) {
               var saveStream = LeadStreamFactory.create(saveFile);
               return codecs.saveAsync(destinationImage, saveStream, RasterImageFormat.bmp, 0)
            })
            .then(function () {

               image.Dispose();
               destinationImage.Dispose();
               codecs.Dispose();
            });
      }
   }
}

[TestMethod]
public async Task StartDitheringExample()
{
   RasterCodecs codecs = new RasterCodecs();
   // Load an image that has BottomLeft ViewPerspective
   string srcFileName = @"Assets\Image1.cmp";
   StorageFile loadFile = await Tools.AppInstallFolder.GetFileAsync(srcFileName);
   RasterImage image = await codecs.LoadAsync(LeadStreamFactory.Create(loadFile));
   RasterColor[] Palette = { RasterColorHelper.Create(0,0,0),
                             RasterColorHelper.Create(255,255,255),
                             RasterColorHelper.Create(255,0,0),
                             RasterColorHelper.Create(0,255,0),
                             RasterColorHelper.Create(0,0,255),
                             RasterColorHelper.Create(255,255,0),
                             RasterColorHelper.Create(0,255,255),
                             RasterColorHelper.Create(255,0,255),
                             RasterColorHelper.Create(128,128,0),
                             RasterColorHelper.Create(0,128,128),
                             RasterColorHelper.Create(128,128,128),
                             RasterColorHelper.Create(128,0,128),
                             RasterColorHelper.Create(128,255,128),
                             RasterColorHelper.Create(128,255,255),
                             RasterColorHelper.Create(255,128,128),
                             RasterColorHelper.Create(255,255,128),
                           };

   // Create the new palletized image.
   RasterImage destinationImage = new RasterImage(RasterMemoryFlags.Conventional, image.Width, image.Height, 4, image.Order, image.ViewPerspective, Palette);

   // Set the dithering method.
   image.DitheringMethod = RasterDitheringMethod.StevensonArce;

   // Initialize the dithering process.
   image.StartDithering(Palette, Palette.Length);

   // Allocate the output buffer for 8-bit data.
   byte[] InBuffer = new byte[image.BytesPerLine];// Buffer to hold the input row.
   byte[] OutBuffer = new byte[destinationImage.BytesPerLine];// Buffer to hold the output row.

   // Use DitherLine method to process each row in the image.
   image.AccessData();
   for (int i = 0; i < image.Height; i++)
   {
      image.GetRow(i, InBuffer, 0, image.BytesPerLine);
      image.DitherLine(InBuffer, 0, OutBuffer, 0);
      destinationImage.SetRow(i, OutBuffer, 0, destinationImage.BytesPerLine);
   }
   // End the dithering process.
   image.StopDithering();
   image.ReleaseData();

   StorageFile saveFile = await Tools.AppLocalFolder.CreateFileAsync("IMAGE1_DitherLine.BMP");
   ILeadStream saveStream = LeadStreamFactory.Create(saveFile);
   await codecs.SaveAsync(destinationImage, saveStream, RasterImageFormat.Bmp, 0);

   image.Dispose();
   destinationImage.Dispose();
   codecs.Dispose();
}

public void StartDitheringExample(RasterImage image, Stream destStream)
{
   RasterColor[] Palette = RasterPalette.Fixed(256);
   // Create the new palletized image.
   RasterImage destinationImage = new RasterImage(RasterMemoryFlags.Conventional, image.Width, image.Height, 8, image.Order, image.ViewPerspective, Palette, null, 0);

   // Set the dithering method.
   image.DitheringMethod = RasterDitheringMethod.StevensonArce;

   // Initialize the dithering process.
   image.StartDithering(Palette, 256);

   // Allocate the output buffer for 8-bit data.
   byte[] InBuffer = new byte[image.Width * 3];// Buffer to hold the input row.
   byte[] OutBuffer = new byte[image.Width];// Buffer to hold the output row.

   // Use DitherLine method to process each row in the image.
   for (int i = 0; i < image.Height; i++)
   {
      image.GetRow(i, InBuffer, 0, image.BytesPerLine);
      image.DitherLine(InBuffer, 0, OutBuffer, 0);
      destinationImage.SetRow(i, OutBuffer, 0, destinationImage.BytesPerLine);
   }
   // End the dithering process.
   image.StopDithering();

   RasterCodecs codecs = new RasterCodecs();
   codecs.Save(destinationImage, destStream, RasterImageFormat.Bmp, 0);

   image.Dispose();
   destinationImage.Dispose();
}

Public Sub StartDitheringExample(ByVal image As RasterImage, ByVal destStream As Stream)
   Dim Palette As RasterColor() = RasterPalette.Fixed(256)
   ' Create the new palletized image.
   Dim destinationImage As RasterImage = New RasterImage(RasterMemoryFlags.Conventional, image.Width, image.Height, 8, image.Order, image.ViewPerspective, Palette, Nothing, 0)

   ' Set the dithering method.
   image.DitheringMethod = RasterDitheringMethod.StevensonArce

   ' Initialize the dithering process.
   image.StartDithering(Palette, 256)

   ' Allocate the output buffer for 8-bit data.
   Dim InBuffer As Byte() = New Byte(image.Width * 3 - 1){} ' Buffer to hold the input row.
   Dim OutBuffer As Byte() = New Byte(image.Width - 1){} ' Buffer to hold the output row.

   ' Use DitherLine method to process each row in the image.
   Dim i As Integer = 0
   Do While i < image.Height
      image.GetRow(i, InBuffer, 0, image.BytesPerLine)
      image.DitherLine(InBuffer, 0, OutBuffer, 0)
      destinationImage.SetRow(i, OutBuffer, 0, destinationImage.BytesPerLine)
      i += 1
   Loop
   ' End the dithering process.
   image.StopDithering()

   Dim codecs As RasterCodecs = New RasterCodecs()
   codecs.Save(destinationImage, destStream, RasterImageFormat.Bmp, 0)

   image.Dispose()
   destinationImage.Dispose()
End Sub

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

RasterImage Class
RasterImage Members
Introduction to Image Processing With LEADTOOLS
Dithering Methods
Codecs.CodecsThumbnailOptions.DitheringMethod property
ImageProcessing.ColorResolutionCommand.DitheringMethod property
RasterDitheringMethod enumeration
RasterDefaults.DitheringMethod property
RasterImage.DitheringMethod property
RasterImage.DitherLine method
RasterImage.StopDithering method
RasterBufferConverter.Convert