fix bugs in direct Fourier method
fix bugs in direct Fourier method

thewtex/tomviz,cjh1/tomviz,mathturtle/tomviz,thewtex/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,cryos/tomviz,cryos/tomviz,cryos/tomviz,mathturtle/tomviz,cjh1/tomviz,mathturtle/tomviz,OpenChemistry/tomviz,cjh1/tomviz,thewtex/tomviz