HistogramCommand Class

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

public class HistogramCommand : Leadtools.ImageProcessing.RasterCommand, Leadtools.ImageProcessing.IRasterCommand

'Declaration
 
Public Class HistogramCommand 
   Inherits Leadtools.ImageProcessing.RasterCommand
   Implements Leadtools.ImageProcessing.IRasterCommand

'Usage
 
Dim instance As HistogramCommand

public sealed class HistogramCommand : Leadtools.ImageProcessing.IRasterCommand

function Leadtools.ImageProcessing.Color.HistogramCommand()

public ref class HistogramCommand : public Leadtools.ImageProcessing.RasterCommand, Leadtools.ImageProcessing.IRasterCommand

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 Leadtools.RasterImage.LowBit and Leadtools.RasterImage.HighBit of this image identify which bits in a 12-bit or 16-bit entry are used. The Leadtools.RasterImage.LowBit and Leadtools.RasterImage.HighBit can be obtained by using the MinMaxCommand or by looking at the corresponding properties in the Leadtools.RasterImage class itself.
Specifically, the table must hold at least 2^(Leadtools.RasterImage.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 Leadtools.RasterImage.LowBit = 2 and Leadtools.RasterImage.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 Leadtools.RasterImage.LowBit = 0 and Leadtools.RasterImage.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.

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

Public Sub HistogramCommandExample()
   Dim codecs As New RasterCodecs()
   codecs.ThrowExceptionsOnInvalidImages = True

   Dim leadImage As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Master.jpg"))

   ' Prepare the command
   Dim command As HistogramCommand = New HistogramCommand
   Dim histogramValues() As Long
   'Create the red-channel histogram.
   command.Channel = HistogramCommandFlags.Red Or HistogramCommandFlags.AllBits

   command.Run(leadImage)
   codecs.Save(leadImage, Path.Combine(LEAD_VARS.ImagesDir, "Result.jpg"), RasterImageFormat.Jpeg, 24)
   histogramValues = command.Histogram

End Sub

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

public void HistogramCommandExample()
   {
      // Load an image
      RasterCodecs codecs = new RasterCodecs();
      codecs.ThrowExceptionsOnInvalidImages = true;

      RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Master.jpg"));

      // Prepare the command
      HistogramCommand command = new HistogramCommand();
      long [] histogramValues;
      //Create the red-channel histogram.
      command.Channel   = HistogramCommandFlags.Red | HistogramCommandFlags.AllBits;
      command.Run(image);
      codecs.Save(image, Path.Combine(LEAD_VARS.ImagesDir, "Result.jpg"), RasterImageFormat.Jpeg, 24);
      histogramValues = command.Histogram;

   }

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

[TestMethod]
public async Task HistogramCommandExample()
{
   // Load an image
   RasterCodecs codecs = new RasterCodecs();
   codecs.ThrowExceptionsOnInvalidImages = true;
   // Load the image
   string srcFileName = @"Assets\Image1.cmp";
   StorageFile loadFile = await Tools.AppInstallFolder.GetFileAsync(srcFileName);
   RasterImage image = await codecs.LoadAsync(LeadStreamFactory.Create(loadFile));

   // Prepare the command
   HistogramCommand command = new HistogramCommand();
   long [] histogramValues;
   //Create the red-channel histogram.
   command.Channel   = HistogramCommandFlags.Red | HistogramCommandFlags.AllBits;
   command.Run(image);

   string destFileName = @"result.jpg";
   StorageFile saveFile = await Tools.AppLocalFolder.CreateFileAsync(destFileName);
   await codecs.SaveAsync(image, LeadStreamFactory.Create(saveFile), RasterImageFormat.Jpeg, 0);

   histogramValues = command.Histogram;
}

public void HistogramCommandExample(RasterImage image, Stream outStream)
{
   // Prepare the command
   HistogramCommand command = new HistogramCommand();
   //Create the red-channel histogram.
   command.Channel = HistogramCommandFlags.Red | HistogramCommandFlags.AllBits;
   command.Run(image);
   // Save result image
   RasterCodecs codecs = new RasterCodecs();
   codecs.Save(image, outStream, RasterImageFormat.Jpeg, 24);
   image.Dispose();

   //This is where the histogram information is stored
   int[] histogramValues = command.Histogram;
}

Public Sub HistogramCommandExample(ByVal image As RasterImage, ByVal outStream As Stream)
   ' Prepare the command
   Dim command As HistogramCommand = New HistogramCommand()
   'Create the red-channel histogram.
   command.Channel = HistogramCommandFlags.Red Or HistogramCommandFlags.AllBits
   command.Run(image)
   ' Save result image
   Dim codecs As RasterCodecs = New RasterCodecs()
   codecs.Save(image, outStream, RasterImageFormat.Jpeg, 24)
   image.Dispose()

   'This is where the histogram information is stored
   Dim histogramValues As Integer() = command.Histogram
End Sub

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