Matlab psf2otf与fft2函数的关系

psf2otf

 Syntax

 Description

fft2

 Syntax

 两者之间的官方解释也说了，psf2otf，其作用是将一个空间点扩散函数转换为频谱面的光学传递函数，执行的也是对PSF的FFT变换。真的只是这样吗？

 大胆假设 小心求证
我们用matlab验证一下，首先我们生成PSF函数（其实就是空间卷积嘛，囧），随便来一个拉普拉斯模板吧，So easy。

 如果使用psf2otf函数呢

 这样两者就一样了。
实际上psf2otf中最后还舍弃由于浮点数运算带来的微小误差。

Matlab中psf2otf源码如下：

[psf, psfSize, outSize] = ParseInputs(varargin{:});

if  ~all(psf(:)==0),

   % Pad the PSF to outSize
   padSize = outSize - psfSize;
   psf     = padarray(psf, padSize, 'post');

   % Circularly shift otf so that the "center" of the PSF is at the
   % (1,1) element of the array.
   psf    = circshift(psf,-floor(psfSize/2));

   % Compute the OTF
   otf = fftn(psf);

   % Estimate the rough number of operations involved in the 
   % computation of the FFT.
   nElem = prod(psfSize);
   nOps  = 0;
   for k=1:ndims(psf)
      nffts = nElem/psfSize(k);
      nOps  = nOps + psfSize(k)*log2(psfSize(k))*nffts; 
   end

   % Discard the imaginary part of the psf if it's within roundoff error.
   if max(abs(imag(otf(:))))/max(abs(otf(:))) <= nOps*eps
      otf = real(otf);
   end
else
   otf = zeros(outSize);
end