Image Scaling module

Description

The Image Scaling module reads the input folder for valid image files and scales the images per the scaling options.

Parameters

Name	Caption
Input Folder	Input folder
Output Folder	Output folder
Output File Type	Output file type
Output File Options	Output file options
Overwrite Results	Overwrite existing results
Input Channels	Input image channels to scale
Image Scaling Function	Image-scaling function
Options for Image Scaling Function	Scaling-function options
Mosaic Preview File	Mosaic preview file
Input Range of Pixel Values	Input range of pixel values
Output Range Type	Output channel type
Output Range of Pixel Values	Output range of pixel values (min,max)
Tail Trimming	Tail trimming percentage

Parameter descriptions

Input Folder

The path and name of the folder of the image files to scale. All valid images in this folder will be scaled.

This parameter is mandatory.

Output Folder

The path and name of the folder to which to write the output files.

Output File Type

The format of the output file.

For more information on the supported file formats, see GDB-supported file formats.

Output File Options

The options to apply when creating the output file or files. The available options are specific to the file format; in each case, the default of no options is allowed.

For more information on the options available for the output file type you specify, see GDB-supported file formats.

Overwrite Results

Select this check box to overwrite the existing output files, if any exist. If this check box is left clear, and an output file exists in the relevant folder, the status of the job displays a message informing you of the existence and name of the output file. The message is also written to the event log of the job.

Input Channels

A comma-delimited list of the image channels to scale. If no value is specified for this parameter, all channels are processed by default.

This parameter is optional.

Image Scaling Function

The type of scaling to perform.

Available options are:

Linear: scales using a linear function
Square: scales using a square function
Square root: scales using a square-root function
Power: scales using a power function with a specified (n) exponent, defined by the Options for Image Scaling Function parameter
Logarithmic: scales using a logarithmic function
Normalized quantization: applies an automatic normalized quantization
Equal-area quantization: applies an equal-area quantization

Options for Image Scaling Function

Additional options for the specified image-scaling function.

When the value of the Image Scaling Function parameter is POW, you must specify a value for this parameter. The value of n must be in the range of 0.1 <= n = 10. POW 2 is equivalent to SQR. POW 0.5 is equivalent to ROOT. POW 1 is equivalent to LIN.

For all other image-scaling functions, this parameter is optional.

Mosaic Preview File

A low-resolution mosaic file created by a successful run of the Mosaic Preparation module.

The module uses the specified preview file to scale all tiles in the input folder. You can use the preview file to verify that no artifacts have been introduced during the scaling process.

This parameter is optional.

Input Range of Pixel Values

The range of pixel values to use to map to the output range. If no value is specified for this parameter, the range of the actual values in the image will be used.

You specify two values for this parameter to define the range: a minimum and a maximum. For example: 5,200

Note: When a value is specified for the Mosaic Preview File parameter, this parameter is ignored.

Output Range Type

The pixel bit-depth of the output processed channels.

Available options are:

8U: 8-bit unsigned integer
16U: 16-bit unsigned integer
16S: 16-bit signed integer
32R: 32-bit real

Output Range of Pixel Values

The minimum and maximum pixel values of the image to be scaled. This parameter works in conjuction with the Output Range Type parameter to produce the minimum set of values as output.

This parameter is optional.

Tail Trimming

The percentage of tail trimming of the low and high ends of the input histogram or histograms before scaling.

Specified as:

TRIM = p0, p1

where:

p0: (left) specifies the percentage of tail trimming of the left (low end) of the input histogram or histograms
p1: (right) defines percentage of tail trimming of the right (high end) of the input histogram or or histograms

These values are between 0 and 100.

For example:

TRIM=1.0, 2.0

represents one percent trimming on the left tail (low end), and two percent trimming on the right tail (high end) .

Note: This parameter applies only when the value selected in the Image Scaling Function list is Linear, Square root, or Logarithmic; otherwise, no trimming is performed.

This parameter is optional.

Details

General job details

Preprocessing requirements

Before running this module, the following requirements must be met to ensure the job processes successfully and produces accurate results:

The bands of the mosaic preview and the image being scaled must be in the same order
The bit depth of the mosaic preview and the image being scaled must be the same

Module details

The Image Scaling module changes the radiometric resolution of the files in the specified input folder. The module computes the histogram of a reference image (the mosaic preview file), then uses that histogram for each image in the input folder. When no reference imagery is provided, a histogram is computed for each input image.

When you are scaling mosaic tiles, it is strongly recommended that you use reference imagery; otherwise, the resulting mosaic tiles will no longer match, from a color-balancing aspect.

Job results

The Image Scaling module produces a series of output files in the specified output folder, one for each file in the input folder.