phantom() - Image Processing

P = phantom(def, n) generates
an image of a head phantom that can be used to test the numerical
accuracy of radon and iradon or
other two-dimensional reconstruction algorithms. P is
a grayscale intensity image that consists of one large ellipse (representing
the brain) containing several smaller ellipses (representing features
in the brain).def is a string that specifies the type of
head phantom to generate. Valid values are'Shepp-Logan' — Test image
used widely by researchers in tomography'Modified Shepp-Logan' (default)
— Variant of the Shepp-Logan phantom in which the contrast
is improved for better visual perceptionn is a scalar that specifies the number of
rows and columns in P. If you omit the argument, n defaults
to 256.P = phantom(E, n) generates
a user-defined phantom, where each row of the matrix E specifies
an ellipse in the image. E has six columns, with
each column containing a different parameter for the ellipses. This
table describes the columns of the matrix.ColumnParameterMeaning
Column 1AAdditive intensity value of the ellipse
Column 2aLength of the horizontal semiaxis of the ellipse 
Column 3bLength of the vertical semiaxis of the ellipse
Column 4x0x-coordinate of the center of the
ellipse
Column 5y0y-coordinate of the center of the
ellipse
Column 6phiAngle (in degrees) between the horizontal semiaxis of
the ellipse and the x-axis of the image
For purposes of generating the phantom, the domains for the x-
and y-axes span [-1,1]. Columns 2 through 5 must
be specified in terms of this range.[P, E] = phantom(...) returns the matrix E used
to generate the phantom.

Syntax

P = phantom(def, n)P = phantom(E, n)[P, E] = phantom(...)

Example

P = phantom('Modified Shepp-Logan',200);
imshow(P)

Output / Return Value

Limitations

Alternatives / See Also

Reference