ColorThresholdCommand Class

Summary

Using any one of eight color spaces, resets those image's pixel component values that fall inside or outside of a specified range.

Syntax

Objective-C

C++/CLI

Java

Python

public class ColorThresholdCommand : RasterCommand

@interface LTColorThresholdCommand : LTRasterCommand

public class ColorThresholdCommand 
    extends RasterCommand

public ref class ColorThresholdCommand : public RasterCommand

class ColorThresholdCommand(RasterCommand):

Remarks

Every color space component may have a different range:

Color Component	Range for 8 bit per component.	Range for 16 bit per component.
RGB
R	0 ... 255	0 ... 65535
G	0 ... 255	0 ... 65535
B	0 ... 255	0 ... 65535
HSV
H	0 ... 360	0 ... 36000
S	0 ... 100	0 ... 10000
V	0 ... 255	0 ... 65535
HLS
H	0 ... 360	0 ... 36000
L	0 ... 255	0 ... 65535
S	0 ... 100	0 ... 10000
XYZ
X	0 ... 255	0 ... 65535
Y	0 ... 255	0 ... 65535
Z	0 ... 255	0 ... 65535
YCrCb
Y	0 ... 255	0 ... 65535
Cr	-128 ... 127	-32768 ... 32767
Cb	-128 ... 127	-32768 ... 32767
YUV
Y	0 ... 255	0 ... 65535
U	-112 ... 111	-28567 ... 28566
V	-138 ... 137	-35337 ... 35336
LAB
L	0 ... 100	0 ... 10000
A	-128 ... 127	-32768 ... 32767
B	-128 ... 127	-32768 ... 32767
CMY
C	0 ... 255	0 ... 65535
M	0 ... 255	0 ... 65535
Y	0 ... 255	0 ... 65535

This class works as follows:

The image is converted to the required color space.
For every pixel, the following operations are performed: Each component is compared with the MinimumRange and MaximumRange values of the appropriate ColorThresholdCommandComponent class.
- If it is inside the range, the component is considered to have "passed" the test.
- If it is outside the range, the component has been rejected". The ColorThresholdCommandFlags.BandReject flag inverts this by making "rejected" components "passed" and vice-versa.
If ColorThresholdCommandFlags.EffectChannel is set, the components are modified independently. If ColorThresholdCommandFlags.EffectAll has been set, the pixel is rejected by the test if any component is rejected. If the pixel/component is rejected, then:
- If ColorThresholdCommandFlags.SetToMinimum is set, the rejected pixel/component is set to 0.
- If ColorThresholdCommandFlags.SetToMaximum is set, the rejected pixel/component is set to 255.
- If ColorThresholdCommandFlags.SetToClamp is set, components less that MinimumRange go to 0 and components greater than MaximumRange go to 255. This would work only with the ColorThresholdCommandFlags.EffectChannel and ColorThresholdCommandFlags.BandBass flags.
This class works for 1, 2, 3, _ 8,16, 24, 32, 48 and 64-bit color images and can support regions for 24 and 48-bit images. If a 24 or 48-bit image has a region the effect will be applied on the region only.
One class is used for each color component. The order is considered to be the same as in the xxx Space name. For example, for RGB Space:
- Components[0] class is used for the Red component.
- Components[1] class is used for the Green component.
- Components[2] class is used for the Blue component.
This command does not support grayscale images.
This command does not support signed images.
This command does not support 1-bit bitonal images.

For more information, refer to Introduction to Image Processing With LEADTOOLS. For more information, refer to Correcting Colors.

Color Threshold Function - Before

Color Threshold Function - After

View additional platform support for this Color Threshold function.

Example

Run the ColorThresholdCommand on an image.

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing.Color; 
 
 
public void ColorThresholdCommandExample() 
{ 
   // Load an image 
   RasterCodecs codecs = new RasterCodecs(); 
   codecs.ThrowExceptionsOnInvalidImages = true; 
 
   RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "ImageProcessingDemo\\Image1.jpg")); 
 
   // Prepare the command 
   ColorThresholdCommandComponent[] Components = new ColorThresholdCommandComponent[3]; 
 
   Components[0] = new ColorThresholdCommandComponent(); 
   Components[0].MinimumRange = 128; 
   Components[0].MaximumRange = 255; 
   Components[0].Flags = 0; 
   Components[1] = new ColorThresholdCommandComponent(); 
   Components[1].MinimumRange = 128; 
   Components[1].MaximumRange = 255; 
   Components[1].Flags = 0; 
   Components[2] = new ColorThresholdCommandComponent(); 
   Components[2].MinimumRange = 128; 
   Components[2].MaximumRange = 255; 
   Components[2].Flags = 0; 
 
   ColorThresholdCommand command = new ColorThresholdCommand(ColorThresholdCommandType.Rgb, Components); 
   //Apply color Threshold effect on the image. 
   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:\LEADTOOLS22\Resources\Images"; 
}