image color balancing

Feature Description

Image color balancing is an image preprocessing technique designed to eliminate color inconsistency caused by different shooting seasons, sensor differences, or varying weather conditions by adjusting the color, brightness, and contrast of multiple images involved in mosaicking, thereby achieving DOM tessellation results with uniform color and visual harmony.

Image color balancing maps and matches the statistical features (such as mean and variance) of the images to be processed to a reference standard through mathematical transformation, achieving consistent color feature adjustment among images. Its main methods include:

  • Template color balancing: Based on a specified reference image with good color effects, adjusts the color distribution of the images to be processed to be similar to the template.
  • Adaptive Color Uniformity: Without specifying a template, the algorithm automatically analyzes the global and local statistics information of all images involved in the mosaic image, obtains an optimized color balance target through adaptive calculation, and processes each image to achieve overall tone balance.

Image color balancing is generally applied in the following scenarios:

  • DOM production and mosaicking: Before seamless mosaicking of multiple orthophotos, color balancing processing is an essential step that can effectively improve the professionalism and visual quality of the result map.
  • Multi-temporal image comparative analysis: When comparative analysis of images of the same area taken at different times is needed, color balancing can reduce color interference caused by lighting and seasonal changes, making ground feature changes easier to identify.

When using image color balancing, the following issues need attention:

  • Supported data format: *.tiff, *.tif, *.img, *.pix.
  • Recommended input images: 8-bit depth, 3-band (red, green, blue) true color image for optimal processing results.
Figure: original image Figure: color balancing template Figure: color balance result

Parameter description

Parameter Name Parameter Interpretation Parameter Type
data type

This parameter is available only when the function is launched from the Satellite Image Processing tab -> DOM Data Production group -> Image Color Balancing.

Select the source of input image data. The following options are provided:

  • Image Files (default): Performs color balancing based on image files in the local directory.
  • Mosaic Dataset: Performs color balancing based on the mosaic dataset in the current workspace.
image files

This parameter is available only when the function is launched from the Satellite Image Processing tab -> DOM Data Production group -> Image Color Balancing, and Data Type is set to Image Files .

Set the local path where image files are stored. After selection, color balancing will be performed on all images that meet the format requirements in the specified path and its sub-paths.

File
image data source

This parameter is available only when the function is launched from the Satellite Image Processing tab -> DOM Data Production group -> Image Color Balancing, and Data Type is set to Mosaic Dataset.

Specify the datasource where the image dataset is located.

Datasource
image data

This parameter is available only when Data Type is set to Mosaic Dataset. If it is a production workflow, only the dataset is displayed and cannot be edited.

Specify the mosaic dataset used for color balancing.

DatasetMosaic
Color Balancing Method

Select the processing mode for color balancing. The following options are provided:

  • Template color balancing: Adjusts the color features of the images to be balanced based on the template file.
  • Adaptive Color Uniformity (default): An adaptive color consistency processing method combining global and local approaches, without the need to specify a color balancing template.
DesktopColorBalanceType
color balancing template

This parameter is available only when Color Balancing Method is set to Template color balancing.

Specify local image files as the color reference template. The system will adjust the images to be balanced based on this template so that their colors are consistent with or highly close to the template.

When the images to be balanced are single-band, only 8-bit unsigned template data is supported as input.

File
color balancing method

This parameter is available only when Color Balancing Method is set to Template color balancing.

Select the specific algorithm for template color balancing. The following options are provided:

  • Color Balance (default): A local image transformation method. It maps the grayscale mean and variance of local image regions to given values, balancing the contrast across different positions of the image, thereby enhancing details in regions with weak grayscale variation.
  • Color Mapping Uniform Color: Can map the colors of a lower-resolution color balancing template to the images to be processed. This method improves processing efficiency while ensuring good color balancing results.
ColorBalanceMethod
block size

Set the block size for color balancing processing. The smaller the block, the more refined the color balancing processing, but the longer it takes. The following options are provided:

  • 64*64: Divides the color balancing area into sub-regions of 64*64.
  • 128*128: Divides the color balancing area into sub-regions of 128*128.
  • 512*512: Divides the color balancing area into sub-regions of 512*512.
  • 1024*1024 (default): Divides the color balancing area into sub-regions of 1024*1024.
  • 2048*2048: Divides the color balancing area into sub-regions of 2048*2048.
  • 4096*4096: Divides the color balancing area into sub-regions of 4096*4096.
  • 8192*8192: Divides the color balancing area into sub-regions of 8192*8192.
BlockSizeOption
red band index Specify the index number representing the red channel in the image. The default value is 0. Integer
green band index Specify the index number representing the green channel in the image. The default value is 1. Integer
blue band index Specify the index number representing the blue channel in the image. The default value is 2. Integer
Brightness

Adjust the brightness of the result image. The value range is [-100,100], and the default value is 0.0.

The larger the value, the higher the brightness of the result image.

Double
Contrast

Adjust the contrast of the result image. The value range is [-100,100], and the default value is 0.0.

The larger the value, the stronger the contrast of the result image.

Double
Saturation

Adjust the saturation of the result image. The value range is [-100,100], and the default value is 0.0.

The larger the value, the stronger the saturation of the result image.

Double
mask data Not checked by default. If checked, a polygon vector dataset can be set as a mask, and the system will exclude pixels within that region before performing color balancing calculation and output. Boolean
Datasource

This parameter is available only when Mask Data is checked. If executing a production workflow, this parameter is not provided.

Specify the datasource where the mask dataset is located.

DataSource
Dataset

This parameter is available only when Mask Data is checked. If executing a production workflow, the mask data in True Color Output is used by default.

Specify the vector polygon dataset used as the mask. The dataset must contain an ImageName field, and the name must correspond to the current image name to be processed.

DatasetVector
color balancing preview Not checked by default. If checked, when executing the workflow or running the tool independently, it will first pause and generate a color balancing preview image based on the set preview resolution for users to preview in a dedicated window. Boolean
Preview Resolution

Set the resolution used for previewing the color balancing effect.

Lower resolution (larger downsampling factor) provides smoother but blurrier previews; higher resolution (smaller downsampling factor) provides slower but clearer previews. This setting is only for preview and does not affect the quality of the final output result.

The following options are provided:

  • Downsample by 4 (default): The preview resolution is 1/4 of the original image.
  • Downsample by 8: The preview resolution is 1/8 of the original image.
  • Downsample by 16: The preview resolution is 1/16 of the original image.
  • Downsample by 32: The preview resolution is 1/32 of the original image.
  • Downsample by 64: The preview resolution is 1/64 of the original image.
  • Downsample by 128: The preview resolution is 1/128 of the original image.
  • Downsample by 256: The preview resolution is 1/256 of the original image.
  • Downsample by 512: The preview resolution is 1/512 of the original image.
OrthoRatioDecreaseMethod
export directory

Set the storage path for the result image after color balancing processing.

If executing a production workflow, the Processing path parameter in Set Image Path or Add orthophoto is used, and it cannot be edited.

File
resampling method

Set the method used for resampling during the imagery process.

Nearest, Bilinear, and Cubic are provided. The default value is Bilinear. For more method introductions, please refer to Resampling Method.

ResampleMethod
result minimum value Set the minimum pixel value in the result image. The default value is 1. Integer
result maximum value Set the maximum pixel value in the result image. The default value is 255. Integer
No Value Set the pixel value for no-value areas in the result image. The default value is 0.0. Double
resolution type

Specify the method for outputting the resulting image resolution. The following options are provided:

  • Original resolution (default): Retains the original resolution of the input image.
  • Fixed Value: Uses the input fixed value as the resolution of the output image.
  • Custom: Specifies output resolutions separately for different satellite sensor types. After selecting this option, a dialog box will pop up for detailed settings. You can click the Add button on the toolbar in the dialog box to add a record; then click the cell in the Satellite sensor type column to select the sensor type; finally, enter the resolution corresponding to the sensor type in the Resolution column cell.
    Note:
    • If the corresponding satellite sensor type is not found, please select the USEDEFINE option. The system will use the resolution set for this option to output data of all satellite sensor types not listed in the list.
    • If processing image data of multiple satellite sensor types simultaneously (e.g., ZY3, GF-2, LandSat), but only setting the resolution for one satellite sensor type (e.g., only setting the resolution for ZY3), then images of other satellite sensor types (e.g., GF-2 and LandSat) will be output using their original resolution.
OrthoRatioType
output format

Set the storage type of the result image. The following options are provided:

  • Not Set: Retains the original image format for output.
  • Tiff/GeoTIFF (default): Indicates that the output result image is stored in Tiff/GeoTIFF format.
  • Erdas Image: Indicates that the output result image is stored in Erdas Image format.
  • PCIDSK: Indicates that the output result image is stored in PCIDSK format.

If executing a production workflow, the Output format parameter in Set Image Path or Add orthophoto is used, and it cannot be edited.

FileType
compression method

When Output format is Tiff/GeoTIFF, set the compression method for the output image.

NONE, DEFLATE, LZW, and JPEG are provided. The default value is NONE. For more method introductions, please refer to Compression method.

If executing a production workflow, the Compression method parameter in Set Image Path or Add orthophoto is used, and it cannot be edited.

CompressMethod
output as original image coordinate

If this parameter is checked, the result data will use the same image coordinate system as the input data. If not checked, the Output coordinate system parameter in Set Image Path or Add orthophoto is used, and it cannot be edited.

Boolean
add results to map window

This parameter is available only when the function is launched from the Imagery tab -> DOM Data Production group -> Image Color Balancing.

Checked by default. After the function execution succeeds, the result data will be automatically added to the current map window for display.

Boolean
create image pyramid

Checked by default. Pyramids will be built for the output image data, thereby improving the zoom browsing speed and display performance of large-volume images.

If executing a production workflow, the Create Image Pyramid parameter in Set Image Path or Add orthophoto is used, and this parameter is not displayed.

Boolean
resampling method

This parameter is available only after Create Image Pyramid is checked.

Specify the resampling method used when creating image pyramids. NONE, Average, Nearest Neighbor, and Gaussian Kernel are provided. The default value is Average. For more method introductions, please refer to Resampling Method.

If executing a production workflow, the Resampling Method parameter in Set Image Path or Add orthophoto is used, and this parameter is not displayed.

ResamplingMethod
asynchronously create statistics

The statistics information of the image is used to optimize the stretch effect during display. If the image has no statistics information, it will be displayed according to the default stretch method, and no stretch display will be applied to 8-bit data.

  • Checked (default): Statistics will be created for the image in the background without affecting workflow execution.
  • Unchecked: Statistics information will be created simultaneously when executing this tool, which may take time.

If executing a production workflow, the Asynchronously create statistics parameter in Set Image Path or Add orthophoto is used, and this parameter is not displayed.

Boolean

Output Result

  • Output the color-balanced image data to the local folder.
  • Automatically create an image color balancing mosaic dataset in the OrthoData datasource based on the output image data.

Related Topics

True Color Output

Image Fusion

Image mosaic