fanbeam
Fan-beam transform
Syntax
描述
[returns the location of fan-beam sensors inF,fan_sensor_positions,fan_rotation_angles] = fanbeam（___)fan_sensor_positionsand the rotation angles where the fan-beam projections are calculated infan_rotation_angles.
例子
计算整个图像上旋转角度的风扇梁投影
Set the IPT preference to make the axes visible.
iptsetpref('ImshowAxesVisible','on')
Create a sample image and display it.
pH =幻影（128）;imshow（ph）
Calculate the fanbeam projections and display them.
[F,Fpos,Fangles] = fanbeam(ph,250); figure imshow(F,[],“XData”，fangles，'ydata'，fpos，...'InitialMagnification','fit') axisnormalXlabel（'Rotation Angles (degrees)'）ylabel（“传感器位置（度）”）Colormap（GCA，热），配色栏
Compute Radon and Fan-beam Projections and Compare Results
Compute fan-beam projections for 'arc' geometry.
I = ones(100); D = 200; dtheta = 45; [Farc,FposArcDeg,Fangles] = fanbeam(I,D,...'fansensorgemetry','arc',...“狂热”,dtheta);
Convert angular positions to linear distance along x-prime axis.
fposarc = d*tan（fposarcdeg*pi/180）;
计算“线”几何形状的风扇束投影。
[Fline,FposLine] = fanbeam(I,D,...'fansensorgemetry','line',...“狂热”,dtheta);
Compute the corresponding Radon transform.
[R,Rpos]=radon(I,Fangles);
说play the three projections at one particular rotation angle. Note the three are very similar. Differences are due to the geometry of the sampling, and the numerical approximations used in the calculations.
图IDX = find（fangles == 45）;绘图（rpos，r（：，idx），...fposarc，farc（：，idx），...fpoSline，fline（：，idx））传奇（'Radon','Arc','Line')
Input Arguments
I—Input image
2-D numeric matrix|2-D逻辑矩阵
输入图像，指定为2-D数字或逻辑矩阵。
D—说tance from fan beam vertex to center of rotation
正数
从风扇梁顶点到旋转中心的像素中的距离，指定为正数。旋转中心是图像的中心像素，定义为地板（（尺寸（i）+1）/2）.Dmust be large enough to ensure that the fan-beam vertex is outside of the image at all rotation angles. See提示有关指定指南D. The figure illustratesD关于一个风扇梁几何形状的风扇梁顶点。
Name-Value Arguments
Specify optional comma-separated pairs of名称，价值参数。Name是the argument name and价值是相应的值。Name必须出现在引号中。您可以按任何顺序指定几个名称和值对参数NAME1，Value1，...，Namen，Valuen.
f = fanbeam（i，d，'fanrotation increment'，5）
风扇梁旋转角度增量in degrees, specified as the comma-separated pair consisting of“狂热”和一个正标量。
Data Types:双倍的
Fan-beam sensor positioning, specified as the comma-separated pair consisting of'fansensorgemetry'and one of the following values.
Output Arguments
提示
作为指南，尝试制作Da few pixels larger than half the image diagonal dimension, calculated as follows.
sqrt(size(I,1)^2 + size(I,2)^2)
The values returned inF是风扇梁投影的数值近似。该算法取决于ra的变换，并插值为风扇梁几何形状。结果取决于所使用的参数。当图像更大时，您可以期望更准确的结果D是larger, and for points closer to the middle of the image, away from the edges.
参考
[1] Kak，A.C。和Slaney，M.，Principles of Computerized Tomographic Imaging，IEEE出版社，纽约，1988年，第92-93页。
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