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RemapHueCommand Class

Summary
Uses a lookup table to change an image's hue values. The saturation and value tables change S and V values only if a particular hue value is marked as non-zero in the Mask property. It is used for all resolutions, including 48 and 64-bit images.
Syntax
C#
VB
Objective-C
C++
Java
public class RemapHueCommand : RasterCommand 
Public Class RemapHueCommand  
   Inherits RasterCommand 
@interface LTRemapHueCommand : LTRasterCommand 
public class RemapHueCommand extends RasterCommand 
public ref class RemapHueCommand : public RasterCommand   
Remarks
  • This command can be used to change a range of colors to another range of colors. For example, it could be used to change all red pixels to any color, where a red pixel can have any brightness (V) and any amount of white (saturation). A red pixel in this case would be RGB(x,y,y) where 0 <= x <(LookUpTableLength - 1) and 0 <= y < x or in the HSV color space HSV(0,x,x) where 0<=x<=(LookUpTableLength - 1)
  • The Mask lookup table identifies which values in the HueTable are valid. If a Mask value is 0, then the corresponding value in the HueTable is ignored. If a Mask value is non-zero, then the corresponding value in the HueTable is used. For example, if a pixel has a hue value of 240 and Mask[240] is nonzero, then the hue value of 240 is replaced with HueTable[240]. Traditionally, hue ranges from 0 to 359. For the lookup table, the range of 0 to 359 is remapped to a range of 0.. LookUpTableLength - 1. For example, if LookUpTableLength = 256
  • This command supports 48 and 64-bit colored images.
  • This command does not support signed data images.
  • This command does not support 32-bit grayscale images.

For more information, refer to Changing Brightness and Contrast.

Example

Run the RemapHueCommand on an image and change all green hues (and hues near green).

C#
VB
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing.Color; 
 
public int INCREMENT_S1(int x, int Length) 
{ 
   return ((x + 1) % Length); 
} 
 
public int DECREMENT_S1(int x, int Length) 
{ 
   return ((x + (Length - 1)) % Length); 
} 
 
public int ADD_S1(int x, int y, int Length) 
{ 
   return ((x + y) % Length); 
} 
 
public void RemapHueCommandCommandExample() 
{ 
   // Load an image 
   RasterCodecs codecs = new RasterCodecs(); 
   codecs.ThrowExceptionsOnInvalidImages = true; 
 
   RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "cannon.jpg")); 
 
   // Prepare the command 
   int[] MaskTable; 
   int[] HueTable; 
   RasterHsvColor hsvRef; 
   int HueGreen, HueChange; 
   int Change; 
   int i, Count; 
   int Length; 
 
   if (image.BitsPerPixel >= 48) 
      Length = 0x10000; 
   else if (!(image.BitsPerPixel == 16 || image.BitsPerPixel == 12)) 
      Length = 256; 
   else if (image.GetLookupTable() != null && image.UseLookupTable) 
      Length = 256; 
   else 
      Length = (1 << image.BitsPerPixel); 
 
   //Allocate tables 
   MaskTable = new int[Length]; 
   HueTable = new int[Length]; 
 
   //Initialize tables 
   for (i = 0; i < Length; i++) 
   { 
      MaskTable[i] = 0; 
      HueTable[i] = i; 
   } 
 
   //Get the hue for green 
   hsvRef = RasterHsvColor.FromRasterColor(new RasterColor(0, 255, 0)); 
 
   HueGreen = hsvRef.H; 
 
   //Obtain new hue   
   hsvRef = RasterHsvColor.FromRasterColor(new RasterColor(255, 128, 0)); 
   Change = (int)hsvRef.H - (int)HueGreen; 
   HueChange = (Change > 0) ? (int)Change : (int)(Change + Length - 1); 
   HueGreen *= (Length - 1) / 255; 
   HueChange *= (Length - 1) / 255; 
 
   //Set values in HueTable, MaskTable  
   HueTable[HueGreen] = (HueTable[HueGreen] + HueChange); 
   MaskTable[HueGreen] = 1; 
 
   //set the hues near green (+/- 15) 
   Count = (15 * (Length - 1)) / 255; 
   for (i = INCREMENT_S1(HueGreen, Length); Count > 0; i = INCREMENT_S1(i, Length), Count--) 
   { 
      HueTable[i] = ADD_S1(HueTable[i], HueChange, Length); 
      MaskTable[i] = 1; 
   } 
 
   Count = (15 * (Length - 1)) / 255; 
   for (i = DECREMENT_S1(HueGreen, Length); Count > 0; i = DECREMENT_S1(i, Length), Count--) 
   { 
      HueTable[i] = ADD_S1(HueTable[i], HueChange, Length); 
      MaskTable[i] = 1; 
   } 
 
   RemapHueCommand command = new RemapHueCommand(MaskTable, HueTable, null, null, Length); 
   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:\LEADTOOLS21\Resources\Images"; 
} 
Imports Leadtools 
Imports Leadtools.Codecs 
Imports Leadtools.ImageProcessing.Color 
 
Public Function INCREMENT_S1(ByVal x As Integer, ByVal Length As Integer) As Integer 
   Return ((x + 1) Mod Length) 
End Function 
 
Public Function DECREMENT_S1(ByVal x As Integer, ByVal Length As Integer) As Integer 
   Return ((x + (Length - 1)) Mod Length) 
End Function 
 
Public Function ADD_S1(ByVal x As Integer, ByVal y As Integer, ByVal Length As Integer) As Integer 
   Return ((x + y) Mod Length) 
End Function 
 
Public Sub RemapHueCommandCommandExample() 
   Dim codecs As New RasterCodecs() 
   codecs.ThrowExceptionsOnInvalidImages = True 
 
   Dim leadImage As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "cannon.jpg")) 
 
   ' Prepare the command 
   Dim MaskTable() As Integer 
   Dim HueTable() As Integer 
   Dim hsvRef As RasterHsvColor 
   Dim HueGreen As Integer 
   Dim HueChange As Integer 
 
   Dim Change As Integer 
   Dim i As Integer 
   Dim Count As Integer 
   Dim Length As Integer 
 
   If (leadImage.BitsPerPixel >= 48) Then 
 
      Length = 65536 
 
   ElseIf (Not (leadImage.BitsPerPixel = 16 Or leadImage.BitsPerPixel = 12)) Then 
      Length = 256 
   ElseIf (IsNothing(leadImage.GetLookupTable) And leadImage.UseLookupTable) Then 
      Length = 256 
   Else 
      Length = (1 << leadImage.BitsPerPixel) 
   End If 
   'Allocate tables 
   ReDim MaskTable(Length - 1) 
   ReDim HueTable(Length - 1) 
 
   'Initialize tables 
   For i = 0 To Length - 1 
      MaskTable(i) = 0 
      HueTable(i) = i 
   Next 
 
   'Get the hue for green 
   hsvRef = RasterHsvColor.FromRasterColor(New RasterColor(0, 255, 0)) 
 
   HueGreen = hsvRef.H 
 
   'Obtain new hue   
   hsvRef = RasterHsvColor.FromRasterColor(New RasterColor(255, 128, 0)) 
   Change = hsvRef.H - HueGreen 
   If (Change > 0) Then 
      HueChange = Change 
   Else 
      HueChange = Change + Length - 1 
   End If 
 
   HueGreen = (HueGreen * (Length - 1)) \ 255 
   HueChange = (HueChange * (Length - 1)) \ 255 
 
   'Set values in HueTable, MaskTable  
   HueTable(HueGreen) = HueTable(HueGreen) + HueChange 
   MaskTable(HueGreen) = 1 
 
   'set the hues near green (+/- 15) 
   i = INCREMENT_S1(HueGreen, Length) 
 
   For Count = (15 * (Length - 1)) \ 255 To 1 Step -1 
      i = INCREMENT_S1(i, Length) 
      HueTable(i) = ADD_S1(HueTable(i), HueChange, Length) 
      MaskTable(i) = 1 
   Next 
 
   i = DECREMENT_S1(HueGreen, Length) 
 
   For Count = (15 * (Length - 1)) \ 255 To 1 Step -1 
 
      i = DECREMENT_S1(i, Length) 
      HueTable(i) = ADD_S1(HueTable(i), HueChange, Length) 
      MaskTable(i) = 1 
   Next 
   Dim command As RemapHueCommand = New RemapHueCommand(MaskTable, HueTable, Nothing, Nothing, Length) 
 
   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:\LEADTOOLS21\Resources\Images" 
End Class 
Requirements

Target Platforms

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Leadtools.ImageProcessing.Color Assembly