ENVI provides various texture filters based on occurrence measures or co-occurrence measures.

Occurrence-Based Filters

Use Occurrence Measures to apply a texture filter that is based on a first-order occurrence measure. The following measures are available: data range, mean, variance, entropy, and skewness. See Texture Metrics Background for more information on how ENVI computes these measures.

  1. From the Toolbox, select Filter > Occurrence Measures. The Texture Input File dialog appears.
  2. Select an input file and perform optional spatial and spectral subsetting, then click OK. The Occurrence Texture Parameters dialog appears.
  3. Specify the texture images to create by selecting the respective check boxes in the Textures to Compute area of the dialog.
  4. Enter the size of the kernel in the Rows (Y) and Cols (x) fields to set the area to consider for the texture evaluation.

Co-occurrence-Based Filters

Use Co-occurrence Measures to apply second-order texture filters that are based on a co-occurrence matrix. These filters include mean, variance, homogeneity, contrast, dissimilarity, entropy, second moment, and correlation. A setting for greyscale quantization levels further allows you to reduce the number of shades of gray required to represent the image. This option also reduces processing time.

See Texture Metrics Background for more information on how ENVI computes these measures.

  1. From the Toolbox, select Filter > Co-occurrence Measures. The Texture Input File dialog appears.
  2. Select an input file and perform optional spatial and spectral subsetting, then click OK. The Co-occurrence Texture Parameters dialog appears.
  3. Specify the texture images to create by selecting the respective check boxes in the Textures to Compute area of the dialog.
  4. Enter the size of the kernel in the Rows (y) and Cols (x) fields.
  5. Enter the X and Y Shift values used to calculate the co-occurrence matrix.
  6. Select a Greyscale Quantization Level (up to 64) used to calculate the co-occurrence matrix. This setting is useful if the greyscale values of the image are spread over a broad range (versus being clustered in a certain range).
  7. Select output to File or Memory.
  8. Click OK. ENVI adds the resulting output to the Layer Manager.

See Also

Adaptive Filters, Convolution and Morphology Filters, Frequency Filters, Texture Metrics Background, LabelEntropyTexture Task, RankStrengthTexture Task, FirstOrderEntropyTexture Task