The intensity profile of an image is the set of intensity values taken from regularly
spaced points along a line segment or multi-line path in an image. To create an
intensity profile, use the
improfile function. This function
calculates and plots the intensity values along a line segment or a multi line path in
an image. You define the line segment (or segments) by specifying their coordinates as
input arguments or interactively using a mouse. For points that do not fall on the
center of a pixel, the intensity values are interpolated. By default,
improfile uses nearest-neighbor interpolation, but you can
specify a different method. (For more information about specifying the interpolation
method, see Resize an Image with imresize Function.)
improfile works best with grayscale and truecolor images.
This example shows how to create an intensity profile for an
image interactively using
Read an image and display it.
I = fitsread('solarspectra.fts'); imshow(I,);
Create the intensity profile. Call
improfile with no
arguments. The cursor changes to cross-hairs when you move it over the
displayed image. Using the mouse, specify line segments by clicking the
improfile draws a line between the endpoints.
When you finish specifying the path, press
Return. In the following figure, the line is
shown in red.
After you finish drawing the line over the image,
improfile displays a plot of the data along the line.
Notice how the peaks and valleys in the plot correspond to the light and
dark bands in the image.
This example shows how to plot the intensity values in an RGB
image. For a single line segment,
improfile plots the intensity
values in a two-dimensional view. For a multi-line path,
improfile plots the intensity values in a
Display an RGB image using
improfile without any arguments and trace a line
segment in the image interactively. In the figure, the black line indicates
a line segment drawn from top to bottom. Double-click to end the line
RGB Image with Line Segment Drawn with improfile
improfile function displays a plot of the intensity
values along the line segment. The plot includes separate lines for the red,
green, and blue intensities. In the plot, notice how low the blue values are
at the beginning of the plot where the line traverses the orange
Plot of Intensity Values Along a Line Segment in an RGB Image