Image Uniform Color

Feature Description

Image uniform color is an image preprocessing technique designed to eliminate tonal inconsistencies caused by different shooting seasons, sensor variations, or weather conditions by adjusting the color, brightness, and contrast of multiple images participating in a mosaic. This results in a uniformly colored and visually coordinated DOM mosaic product.

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

  • Template Color Balancing: Based on a specified, high-quality reference image, it adjusts the color distribution of the images to be processed to resemble that of the template.
  • Adaptive Color Uniformity: Without specifying a template, the algorithm automatically analyzes the global and local color statistical information of all images participating in the mosaic. It calculates an optimized color balancing target through adaptive computation and processes each image to achieve overall tonal balance.

Image uniform color is generally applied in the following scenarios:

  • DOM Production and Mosaic: Performing color balancing is an essential step before seamless mosaic of multiple orthophotos, effectively enhancing the professionalism and visual appeal of the final map.
  • Multi-temporal Image Comparative Analysis: When comparing images of the same area taken at different times, color balancing can reduce color interference from lighting and seasonal changes, making changes in ground features easier to identify.

When using image uniform color, please note the following issues:

  • Supported data formats: *.tiff, *.tif, *.img, *.pix.
  • Recommended input images: 8-bit depth, 3-band (red, green, blue) true color images for optimal processing results.
  • Please create an Image Production Workflow first to use this function.

SuperMap iDesktopX11i(2023) version begins to support.

Figure: Original Image Figure: Color Balancing Template Figure: Color Balance Result

Function Entrance

Satellite Image Processing tab->DOM Data Production group->Image Uniform Color.

Parameter Description

Parameter Name Parameter Interpretation Parameter Type
Data Type

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

Select the source of input image data, providing the following options:

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

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

Set the local path storing the image files. After selection, color balancing will be performed on all images meeting the format requirements under the specified path and its subpaths.

File
Image Data Source

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

Specify the data source where the image dataset is located.

Datasource
Image Data

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

Specify the mosaic dataset to be used for color balancing.

DatasetMosaic
Color Balancing Method

Select the processing mode for color balancing, providing the following options:

  • Template Color Balancing: Adjust the color features of the images to be balanced based on a template file.
  • Adaptive Color Uniformity (Default): An adaptive method combining global and local color consistency processing, no need to specify a color balancing template.
DesktopColorBalanceType
Color Balancing Template

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

Specify a local image file as the color reference template. The system will adjust the images to be balanced based on this template, making their colors consistent with or highly similar to the template.

File
Color Balancing Algorithm

 

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

Select the specific algorithm for template-based color balancing, providing the following options:

  • Uniform Light And Color (Default): A local image transformation method. It maps the grayscale mean and variance of local image areas to given values, making the contrast at different positions of the image tend to be balanced, thereby enhancing details in areas with weak grayscale.
  • Color Mapping Uniform Color: Maps the colors of a lower-resolution color balancing template onto the images to be processed. This method ensures good color balancing results while improving processing efficiency.
ColorBalanceMethod
Block Size

Set the block size during color balancing processing. The smaller the block, the finer the processing, but the longer the time consumption. Provides the following options:

  • 64*64: Divide the color balancing area into sub-regions of size 64*64.
  • 128*128: Divide the color balancing area into sub-regions of size 128*128.
  • 512*512: Divide the color balancing area into sub-regions of size 512*512.
  • 1024*1024 (Default): Divide the color balancing area into sub-regions of size 1024*1024.
  • 2048*2048: Divide the color balancing area into sub-regions of size 2048*2048.
  • 4096*4096: Divide the color balancing area into sub-regions of size 4096*4096.
  • 8192*8192: Divide the color balancing area into sub-regions of size 8192*8192.
BlockSizeOption
Red Band Index Specify the index number representing the red channel in the image, default is 0. Integer
Green Band Index Specify the index number representing the green channel in the image, default is 1. Integer
Blue Band Index Specify the index number representing the blue channel in the image, default is 2. Integer
Brightness

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

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

Double
Contrast

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

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

Double
 
Saturation

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

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

Double
Mask Data Unchecked by default. If checked, you can set a polygon vector dataset as a mask. The system will exclude pixels within this area during color balancing calculation and output. Boolean
Data Source

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

Specify the data source where the mask dataset is located.

DataSource
Dataset

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

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

DatasetVector
Uniform Color Preview Unchecked by default. When checked, the process will pause before execution (or when running the tool separately) and generate a color-balanced preview image based on the set preview resolution for users to preview in a dedicated window. Boolean
Color Balancing Resolution

Set the resolution used when previewing the color balancing effect.

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

The provided options are as follows:

  • Downsample 4x (Default): Preview resolution is 1/4 of the original image.
  • Downsample 8x: Preview resolution is 1/8 of the original image.
  • Downsample 16x: Preview resolution is 1/16 of the original image.
  • Downsample 32x: Preview resolution is 1/32 of the original image.
  • Downsample 64x: Preview resolution is 1/64 of the original image.
  • Downsample 128x: Preview resolution is 1/128 of the original image.
  • Downsample 256x: Preview resolution is 1/256 of the original image.
  • Downsample 512x: 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, then use the Processing Path parameter from Set the Image Path or Add Orthophoto, and it cannot be edited.

File
Resampling Method

Set the method used for resampling during imagery processing.

Provides Nearest, Bilinear, Cubic three options, default is Bilinear. For more method introductions, please refer to Resampling Method.

ResampleMethod
Result Minimum Value Set the minimum pixel value in the result image, default is 1. Integer
Result Maximum Value Set the maximum pixel value in the result image, default is 255. Integer
No Value Set the pixel value for no-data areas in the result image, default is 0.0. Double
Resolution Type

Specify the method for outputting the resulting image resolution. Provides the following options:

  • Original Resolution (Default): Keep the original resolution of the input image.
  • Fixed Value: Use an input fixed value as the output image resolution.
  • Custom: Specify output resolutions separately based on different satellite sensor types. Selecting this option will pop up a dialog for detailed settings. In the dialog, you can click the Add button on the toolbar to add a record; then click the cell in the Satellite Sensor Type column to select the sensor type; finally, input the corresponding resolution for the sensor type in the cell of the Resolution column.
    Notes:
    • 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 all data of satellite sensor types not listed.
    • If processing image data from multiple satellite sensor types simultaneously (e.g., ZY3, GF-2, LandSat) but only set the resolution for one of them (e.g., only set for ZY3), then images from 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. Provides the following options:

  • Not Set: Output while retaining the original image format.
  • Tiff/GeoTIFF (Default): Means the output result image is stored in Tiff/GeoTIFF format.
  • Erdas Image: Means the output result image is stored in Erdas Image format.
  • PCIDSK: Means the output result image is stored in PCIDSK format.

If executing a production workflow, then use the Output Format parameter fromSet the Image Path orAdd Orthophoto, and it cannot be edited.

FileType
Compression Method

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

Provides NONE, DEFLATE, LZW, JPEG four options, default is NONE. For more method introductions, please refer to Compression Method.

If executing a production workflow, then use the Compression Method parameter fromSet the Image Path orAdd Orthophoto, and it cannot be edited.

CompressMethod
Output As Original Image Coordinate

Check this parameter, the result data will use the same image coordinate system as the input data. If unchecked, then use the Output Coordinate System parameter from Set the Image Path or Add Orthophoto, and it cannot be edited.

Boolean
Add Results To Map Window

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

Checked by default. After the function executes successfully, the result data is automatically added to the current map window for display.

Boolean
Create An Image Pyramid

Checked by default. Will build pyramids for the output image data, thereby improving zoom browsing speed and display performance for large-volume images.

If executing a production workflow, then use the Create An Image Pyramid parameter fromSet the Image Path orAdd Orthophoto, and this parameter is not displayed.

Boolean
Resampling Method

This parameter is only available after checking Create An Image Pyramid.

Specify the resampling method used when creating an image pyramid. Provides NONE, Average, Nearest Neighbor, Gaussian Kernel, default is Average. For more method introductions, please refer to Resampling Method.

If executing a production workflow, then use the Resampling Method parameter fromSet the Image Path orAdd Orthophoto, and this parameter is not displayed.

ResamplingMethod
Asynchronously Create Statistics

Image statistics information is used to optimize the stretch effect during display. If the image lacks statistics information, it will be displayed using the default stretch method, and 8-bit data will not be stretched for display.

  • Checked (Default): Will create statistics for the image in the background, without affecting workflow execution.
  • Unchecked: Create statistics information while executing this tool, which may consume time.

If executing a production workflow, then use the Asynchronously Create Statistics parameter fromSet the Image Path orAdd Orthophoto, and this parameter is not displayed.

Boolean

Output Result

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

Related Topics

True Color Output

Image Fusion

Image Mosaic