%計算出YX，v，u。計算結果可以畫出圖形
function?[YXvu]=fft_piv（imr1imr2nx_windowny_windowoverlap_xoverlap_y）
%check?image?size
%nx圖片的長度
%subwindow_x小框的起始x坐標
%X_xsize網格的X坐標
%x_center小框的一半
%x_end矢量的終點
now=cputime;
nx=size（imr11）;
ny=size（imr12）;
nx2=size（imr21）;
ny2=size（imr22）;
if（nx~=nx2）|（ny~=ny2）
????error（‘Error:image?sizes?are?different!!‘）;
end
if?overlap_x>0.9|overlap_y>0.9
????error（‘Error:the?overlap?ration?is?too?large!!‘）;
end
if（nx_window<8）|（ny_window<8）
????error（‘Error:subwindow?is?too?small!!‘）;
end
if（nx_window>250）|（ny_window>250）
????error（‘Error:subwindow?is?too?large!!‘）;
end
x_center=floor（nx_window/2）;
y_center=floor（ny_window/2）;
overlapx=floor（nx_window*overlap_x）;
overlapy=floor（ny_window*overlap_y）;
subwindow_x=1;
subwindow_y=1;
X_xsize=0;
X_ysize=0;
for?subwindow_x=1:overlapx:（nx-nx_window）
????X_xsize=X_xsize+1;
end
????for?subwindow_y=1:overlapy:（ny-ny_window）
????????X_ysize=X_ysize+1;
????end
????X=ones（X_xsizeX_ysize）;
????Y=on