运行如下命令：
[x,y]=meshgrid(1:15,1:15);
tri = delaunay(x,y);
z = peaks(15);
z(z<0)=nan;
H = trisurf(tri,x,y,z);
view(2);
set(gcf,'color','none');
set(gca,'color','none');
grid off;
axis off;
axis([min(x(:)) max(x(:)) min(y(:)) max(y(:))]);
set(gcf,'InvertHardcopy','off');
set(gcf,'paperpositionmode','auto');
set(gca,'position',[0.0 0.0 1 1]);
saveas(gcf,'output.png');
保存为output.png时，灰色网格部分就变成灰色的了。但导入ppt,word等软件是，此灰色部分仍会显示。
[A,MAP] =imread('output.png');
[dim1,dim2,dim3]=size(A);
Alpha=ones(dim1,dim2);