Legacy Documentation

Digital Image Processing (2000)

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RegionProcessing

The argument roi may be defined by graphics primitives Circle, Disk, Point, Line, Rectangle, and Polygon, or by a list of integer coordinate pairs (i.e., vertexes of a polygon).
Padding helps eliminate edge effects when operations such as DiscreteConvolve are applied to the region-of-interest. Margins defined by pad should be at least one less than the dimensions of the filter used in the filtering operation. The argument pad must be a pair of integers.
The argument img may be a matrix or ImageData expression.
See also User's Guide 5.6.
Modified in Version 2.1.

Examples

This loads the package.
In[1]:=
This creates a small data array.
In[2]:=
Here we use a pure function (see pure functions tutorial in Documentation Center) to change the values of all the elements on a major diagonal of matrix A to a constant value a.
In[3]:=
Out[3]//MatrixForm=Out[3]//MatrixForm=
Here, we change the values in an L-shaped region using Threshold.
In[4]:=
Out[4]//MatrixForm=Out[4]//MatrixForm=
This loads an example color image.
In[5]:=
Here we apply a different function to each channel of a color image. Specifically, in a small rectangular region of the image, every pixel is set to a new constant value (for a more convenient method of changing pixel values in a region-of-interest see RegionFill).
In[6]:=
Out[6]//InputForm=Out[6]//InputForm=
This loads another example image.
In[7]:=
The following calculation demonstrates the difference when region-of-interest processing is performed with and without padding, respectively. Note, in particular, that when padding is used, the effect is a visual blending at the edges of the region-of-interest.
In[8]:=
Out[8]=Out[8]=