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HistogramCommand Class
See Also  Members   Example 




Creates an array that charts how many times each intensity level occurs in an image. This class can chart red, green, and blue separately or together. It is used for all resolutions, including 12 and 16-bit grayscale.

Syntax

Visual Basic (Declaration) 
Public Class HistogramCommand 
   Inherits RasterCommand
   Implements IRasterCommand 
Visual Basic (Usage)Copy Code
Dim instance As HistogramCommand
C# 
public class HistogramCommand : RasterCommand, IRasterCommand 
Managed Extensions for C++ 
public __gc class HistogramCommand : public RasterCommand, IRasterCommand 
C++/CLI 
public ref class HistogramCommand : public RasterCommand, IRasterCommand 

Example

Visual BasicCopy Code
ImageProcessing.Color.HistogramCommand
   Public Sub HistogramCommandExample()
      RasterCodecs.Startup()
      Dim codecs As New RasterCodecs()
      codecs.ThrowExceptionsOnInvalidImages = True

      Dim leadImage As RasterImage = codecs.Load("C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\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, "C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\Result.jpg", RasterImageFormat.Jpeg, 24)
      histogramValues = command.Histogram

      RasterCodecs.Shutdown()
   End Sub
C#Copy Code
ImageProcessing.Color.HistogramCommand 
      public void HistogramCommandExample() 
      { 
         // Load an image 
         RasterCodecs.Startup(); 
         RasterCodecs codecs = new RasterCodecs(); 
         codecs.ThrowExceptionsOnInvalidImages = true; 
 
         RasterImage image = codecs.Load(@"C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\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, @"C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\Result.jpg", RasterImageFormat.Jpeg, 24); 
         histogramValues = command.Histogram; 
 
         RasterCodecs.Shutdown(); 
      }

Remarks

  • 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 - 15bit 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.
For more information, refer to Changing Brightness and Contrast.
For more information, refer to Grayscale Images.

Inheritance Hierarchy

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

Requirements

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

See Also