2.6.1.4 imgColorlevel
Menu Information
Image: Adjustments: Color Level
Brief Information
Apply user-defined color levels to image
Command Line Usage
1. imgColorlevel c:=green w:=90 b:=20 g:=80;
2. imgColorlevel c:=red w:=80 b:=20 oimg:=<new>;
X-Function Execution Options
Please refer to the page for additional option switches when accessing the x-function from script
Variables
Display Name
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Variable Name
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I/O and Type
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Default Value
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Description
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Input Matrix
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img
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Input
Image
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<active>
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Specifies the image to manipulate. By default, the input image is the active image.
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Channel
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c
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Input
int
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master
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Specifies the color channel to apply color leveling.
Option list
- M:Master
- The master channel
- R:Red
- The red channel
- G:Green
- The green channel
- blue:Blue
- The blue channel
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HiClip(%)
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w
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Input
double
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100
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Specifies the percentage of highlight levels, which will be remapped to max level during color leveling.
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LoClip(%)
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b
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Input
double
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0
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Specifies the percentage of shadow levels, which will be remapped to min level during color leveling.
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Gamma
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g
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Input
double
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1
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Specifies the gamma value used to remap the mid-tone values.
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Output Image
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oimg
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Output
Image
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<input>
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Specifies the output image.
See the syntax here.
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Level Report
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cl
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Output
ReportData
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[<new>]<new>!
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Specifies the leveling report.
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Description
The imgColorlevel function applies color leveling to an image, which can alter the highlights, midtones and shadows of a color channel and thus can be used to enhance the color of the image. For example, if the input image has too few highlights in its green channel (you can judge that from the histogram or directly from the input image), you can set the HiClip(%) variable to a number less than 100 to boost the highlights.
Examples
In this example, the input image has too few highlights in the green channel. We can tell this from the image view of the input image and the histogram of its green channel. To boost the green highlights, we use the imgColorlevel X-Function.
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Original image
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Histogram of green channel in original image
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Before using the X-function, we first decide a proper HiClip(%) to use. The histogram shows that there are very few pixels whose green levels are not less than 224. So we decide to remap the color levels that are not less than 224 to the max level (255). We compute the value of HiClip(%) as follows:
In other words, we decide to set HiClip(%) to 88.
Then, we can use the imgColorlevel X-Function as follows:
- Make the input image active. Then, we choose Image: Adjustment: Color Level from the Origin menu. This opens the dialog of the X-Function.
- Select Green with the Channel drop-down list. Enter 88 in the HiClip(%) box. Click OK to close the dialog. Then the input image is replaced by the output image.
We can see there are more green highlights now.
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Output image
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Histogram of green channel in output image
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The leveling report:
Algorithm
The computation uses L_ColorLevelBitmap() function from LEADTOOLS Main API. For more information, please refer to the LEADTOOLS Main API Help file, Version 14 and read the following topic: L_ColorLevelBitmap.
References
LEADTOOLS Main API Help file, Version 14
Related X-Functions
imgLevel, imgAutoLevel
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