2.6.1.1 imgAutoLevel

Menu Information

Image: Adjustments: Auto Level

Brief Information

Apply auto leveling to image

Command Line Usage

1. imgAutoLevel auto:=intensity;

2. imgAutoLevel img:=[Mbook1]Msheet1!Mat(1) auto:=contrast oimg:=<new>;

Variables

Display
Name
Variable
Name
I/O
and
Type
Default
Value
Description
Input Matrix img

Input

Image

<active>

Specifies the image to be manipulated and the default input is the active image.

Auto Level auto

Input

int

level

Specifies the leveling method.
Option list

  • L:Level
    Performs leveling on the individual R, G and B channels, treating each of the R, G and B channels as a individual entity. It introduces color cast on the image.
  • C:Contrast
    Performs leveling on the MASTER channel (the grayscale values of the pixels). No color cast will be introduced.
  • I:Intensity
    Performs leveling on the RGB channel (the sum of the R, G, and B channels). No color cast will be introduced.
Output Image oimg

Output

Image

<input>

Specifies the output image. By default, it is the same as the input image. See the syntax here.

Level Report cl

Output

ReportData

<new>

Specifies the leveling report.


Description

The imgAutoLevel function applies auto-leveling to an image. It makes the dark values darker and the light values lighter. The function automatically enhances shadows and brightens image by 0.5%. It enhances the contrast and intensity by using the histogram of the image and a color distribution-based algorithm.

The imgLevel function can customize the percentage of white pixels and black pixels to clip from the input image to apply leveling to an image.

Examples

In this example, we use the imgAutoLevel function to increase the contrast of the input image:

When the input image is active, select Image: Adjustments: Auto Level: Contrast. The X-Function is applied and the image is altered. We can see that the contrast has been improved than before.

ImgAutoLevel help English files image002.jpg
ImgAutoLevel help English files image004.jpg
The original image
The output image


Algorithm

When auto-leveling is applied, 0.5% of the black pixels and 0.5% of the white pixels in the input image is clipped. The computation uses L_AutoColorLevelBitmap()from LEADTOOLS Main API. For more information, please refer to the LEADTOOLS Main API Help file, Version 14 and read the following topic: L_AutoColorLevelBitmap.

References

LEADTOOLS Main API Help file, Version 14

Related X-Functions

imgLevel, imgColorlevel