ColorLevelCommand Class

Applies color leveling to an image. It changes the image shadows, midtones and highlights. This function is useful for pre-processing images for the purpose of improving barcode recognition results.

Object Model

Syntax

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

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

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

'Usage
 
Dim instance As ColorLevelCommand

public sealed class ColorLevelCommand : Leadtools.ImageProcessing.IRasterCommand

function Leadtools.ImageProcessing.Color.ColorLevelCommand()

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

Remarks

The members of the ColorLevelCommandData class tell the ColorLevelCommand what constitutes shadows, midtones, and highlights and how to remap the shadows, midtones and highlights.
Control the amount of image balance and leveling by controlling the values of the MinimumInput, MaximumInput, MinimumOutput, MaximumOutput, and Gamma members of the ColorLevelCommandData class.
- The MinimumInput property of the ColorLevelCommandData class defines what the method interprets as shadows for that color channel. Any value less than or equal to MinimumInput is considered a shadow.
- The MaximumInput property of the ColorLevelCommandData class defines what the method interprets as highlights for that color channel. Any value greater than or equal to MaximumInput is considered a highlight.
- The value of the MaximumInput property must be greater than the value of the MinimumInput property by at least 2.
- Midtones are those values between MinimumInput and MaximumInput.
- The MinimumOutput property is the value to which the shadows will be mapped.
- The MaximumOutput property is the value to which the highlights will be mapped.
- The Gamma property is used to modify the midtone values
If only ColorLevelCommandFlags.Master is set in the Flags property, then the rest of the channels will still be affected.
If the image is a grayscale image, then you must set ColorLevelCommandFlags.Master in the Flags property, otherwise the class will not have any effect.
If MinimumOutput > MaximumOutput then the image's shadows and highlights will be inverted.
This command 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 signed data images.

For more information, refer to Changing Brightness and Contrast. For more information, refer to Correcting Colors.

Example

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

Public Sub ColorLevelCommandExample()
   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 blue As ColorLevelCommandData = New ColorLevelCommandData
   Dim master As ColorLevelCommandData = New ColorLevelCommandData
   ' Specify Image levels
   blue.MinimumInput = 20
   blue.MaximumInput = 200
   blue.MinimumOutput = 0
   blue.MaximumOutput = 255
   blue.Gamma = 100
   ' Master will cause the image to be Inversed
   master.MinimumInput = 0
   master.MaximumInput = 255
   master.MinimumOutput = 255
   master.MaximumOutput = 0
   master.Gamma = 100
   ' Level the Blue and Master channels
   Dim command As ColorLevelCommand = New ColorLevelCommand(master, Nothing, Nothing, blue, ColorLevelCommandFlags.Blue Or ColorLevelCommandFlags.Master)
   command.Run(leadImage)
   codecs.Save(leadImage, Path.Combine(LEAD_VARS.ImagesDir, "Result.jpg"), RasterImageFormat.Jpeg, 24)

End Sub

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

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

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

      // Prepare the command
      ColorLevelCommandData blue    = new ColorLevelCommandData();
      ColorLevelCommandData master  = new ColorLevelCommandData();
      //Specify Image levels
      blue.MinimumInput    = 20;
      blue.MaximumInput    = 200;
      blue.MinimumOutput   = 0;
      blue.MaximumOutput   = 255;
      blue.Gamma           = 100;
      // Master will cause the image to be Inversed
      master.MinimumInput  = 0;
      master.MaximumInput  = 255;
      master.MinimumOutput = 255;
      master.MaximumOutput = 0;
      master.Gamma         = 100;
      // Level the Blue and Master channels
      ColorLevelCommand command = new ColorLevelCommand(master, null, null, blue, ColorLevelCommandFlags.Blue | ColorLevelCommandFlags.Master);
      command.Run(image);
      codecs.Save(image, Path.Combine(LEAD_VARS.ImagesDir, "Result.jpg"), RasterImageFormat.Jpeg, 24);

   }

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

[TestMethod]
public async Task ColorLevelCommandExample()
{
   // 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
   ColorLevelCommandData blue    = new ColorLevelCommandData();
   ColorLevelCommandData master  = new ColorLevelCommandData();
   //Specify Image levels
   blue.MinimumInput    = 20;
   blue.MaximumInput    = 200;
   blue.MinimumOutput   = 0;
   blue.MaximumOutput   = 255;
   blue.Gamma           = 100;
   // Master will cause the image to be Inversed
   master.MinimumInput  = 0;
   master.MaximumInput  = 255;
   master.MinimumOutput = 255;
   master.MaximumOutput = 0;
   master.Gamma         = 100;
   // Level the Blue and Master channels
   ColorLevelCommand command = new ColorLevelCommand(master, null, null, blue, ColorLevelCommandFlags.Blue | ColorLevelCommandFlags.Master);
   command.Run(image);

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

public void ColorLevelCommandExample(RasterImage image, Stream outStream)
{
   // Prepare the command
   ColorLevelCommandData blue    = new ColorLevelCommandData();
   ColorLevelCommandData master  = new ColorLevelCommandData();
   //Specify Image levels
   blue.MinimumInput    = 20;
   blue.MaximumInput    = 200;
   blue.MinimumOutput   = 0;
   blue.MaximumOutput   = 255;
   blue.Gamma           = 100;
   // Master will cause the image to be Inversed
   master.MinimumInput  = 0;
   master.MaximumInput  = 255;
   master.MinimumOutput = 255;
   master.MaximumOutput = 0;
   master.Gamma         = 100;
   // Level the Blue and Master channels
   ColorLevelCommand command = new ColorLevelCommand(master, null, null, blue, ColorLevelCommandFlags.Blue | ColorLevelCommandFlags.Master);
   command.Run(image);
   // Save result image
   RasterCodecs codecs = new RasterCodecs();
   codecs.Save(image, outStream, RasterImageFormat.Jpeg, 24);
   image.Dispose();
}

Public Sub ColorLevelCommandExample(ByVal image As RasterImage, ByVal outStream As Stream)
   ' Prepare the command
   Dim blue As ColorLevelCommandData = New ColorLevelCommandData()
   Dim master As ColorLevelCommandData = New ColorLevelCommandData()
   'Specify Image levels
   blue.MinimumInput = 20
   blue.MaximumInput = 200
   blue.MinimumOutput = 0
   blue.MaximumOutput = 255
   blue.Gamma = 100
   ' Master will cause the image to be Inversed
   master.MinimumInput = 0
   master.MaximumInput = 255
   master.MinimumOutput = 255
   master.MaximumOutput = 0
   master.Gamma = 100
   ' Level the Blue and Master channels
   Dim command As ColorLevelCommand = New ColorLevelCommand(master, Nothing, Nothing, blue, ColorLevelCommandFlags.Blue Or ColorLevelCommandFlags.Master)
   command.Run(image)
   ' Save result image
   Dim codecs As RasterCodecs = New RasterCodecs()
   codecs.Save(image, outStream, RasterImageFormat.Jpeg, 24)
   image.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