Run the HistogramCommand on an image to get the red-channel histogram.

Visual Basic

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Public Sub HistogramCommandExample()    RasterCodecs.Startup()    Dim codecs As New RasterCodecs()    codecs.ThrowExceptionsOnInvalidImages = True    Dim leadImage As RasterImage = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "Master.jpg")    ' Prepare the command    Dim command As HistogramCommand = New HistogramCommand    Dim histogramValues() As Integer    'Create the red-channel histogram.    command.Channel = HistogramCommandFlags.Red Or HistogramCommandFlags.AllBits    command.Run(leadImage)    codecs.Save(leadImage, LeadtoolsExamples.Common.ImagesPath.Path + "Result.jpg", RasterImageFormat.Jpeg, 24)    histogramValues = command.Histogram    RasterCodecs.Shutdown() End Sub

C#

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public void HistogramCommandExample()  {     // Load an image     RasterCodecs.Startup();     RasterCodecs codecs = new RasterCodecs();     codecs.ThrowExceptionsOnInvalidImages = true;       RasterImage image = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "Master.jpg");       // Prepare the command     HistogramCommand command = new HistogramCommand();     int [] histogramValues;     //Create the red-channel histogram.     command.Channel   = HistogramCommandFlags.Red | HistogramCommandFlags.AllBits;     command.Run(image);     codecs.Save(image, LeadtoolsExamples.Common.ImagesPath.Path + "Result.jpg", RasterImageFormat.Jpeg, 24);     histogramValues = command.Histogram;       RasterCodecs.Shutdown();  }

• For 1, 2, 3, 4, 5, 6, 7, 8, 16, 24, and 32 bit color images, intensity levels range from 0 to 255. Therefore, the resulting array has 256 items, indexed by intensity value. The value of each item is the number of occurrences of the intensity level.
• For 48 and 64-bit images, the intensity levels range from 0 to 65535. Therefore, the resulting array has 65536 items, indexed by intensity value. The value of each item is the number of occurrences of the intensity level.
• This class also works on 12 and 16-bit grayscale images. Intensity values in these images can range from 0 to (2^16 - 1) for 16-bit grayscale or from 0 to (2^12 - 1) for 12- bit grayscale. The LowBit and HighBit of this image identify which bits in a 12-bit or 16-bit entry are used. The LowBit and HighBit can be obtained by using the MinMaxCommand or by looking at the corresponding properties in the RasterImage class itself.
• Specifically, the table must hold at least 2^(HighBit - LowBit + 1) entries if HistogramCommandFlags.LowHighBits is set in the Channel Property. If HistogramCommandFlags.AllBits is set in the Channel Property, the table must hold at least 4096 for 12-bit images and 65536 for 16-bit images.
• For example, suppose HistogramCommandFlags.LowHighBits is set in the Channel property and you have a 16-bit grayscale image with LowBit = 2 and HighBit = 7. There are 2^(7-2+1) = 64 possible grayscale intensities. The table must therefore hold at least 64 entries. The number of grayscale values with bits 2 - 7 set to 0 can be found in Histogram [0]. The number of grayscale values with bit 2 set to 1 and bits 3 - 7 set to 0 can be found in Histogram [1], and so on up to Histogram [63]. Since the low bit is 2 and the high bit is 7, bits 0, 1, and bits 8 - 15 must all be 0. Therefore the values set in bits 2 - 7 determine the intensities present in the image. In the table below, the gray columns represent those bits that are always 0 for the image. The columns bit 7 through bit 2 represent possible settings for those bits. The last column gives the location within the Histogram array of the number of grayscale values having the corresponding settings. For example, Histogram [0] contains the number of grayscale values of intensity 0 (all bits set to 0). Histogram [1] contains all the grayscale values with intensity 4 (the 2 bit position set to 1). Histogram [2] contains all the grayscale values with intensity 8 (the 3 bit set to 1 and the remaining bits set to 0) and so on.

  bits 8 - 15	bit 7	bit 6	bit 5	bit 4	bit 3	bit 2	bit 1	bit 0	count location in Histogram
  all 0s	0	0	0	0	0	0	0	0	Histogram [0]
  all 0s	0	0	0	0	0	1	0	0	Histogram [1]
  all 0s	0	0	0	0	1	0	0	0	Histogram [2]
  all 0s	0	0	0	0	1	1	0	0	Histogram [3]
  all 0s	0	0	0	1	0	0	0	0	Histogram [4]
  _	0	0	0	0	0	0	_	_	and so on
  all 0s	1	1	1	1	1	1	0	0	Histogram [63]

• As another example, suppose you have a 16-bit grayscale image with LowBit = 0 and HighBit = 15. The table must hold 2^16 = 65,536 integer values.
• This class 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.
• This command does not support 32-bit grayscale images.

System.Object
   Leadtools.ImageProcessing.RasterCommand
      Leadtools.ImageProcessing.Color.HistogramCommand

Target Platforms: Microsoft .NET Framework 2.0, Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

Reference