【求助】图片上画矢量

[taotaofu]

I want to draw vectors on the picture '1.tif', I use 'hold on' to do it, but unfortunately,I cannot get the results, does anyone know what is the problem?

我想在图片上画矢量,程序如下,不过遗憾的是不能实现,是不是我的图片读入有问题呢?请指教,谢谢!



I=imread('E:\velocity profile\T600\gas_liquid\0.8%(wt.)_SDS\1.tif');
hold on
quiver(a(:,1),a(:,2),a(:,3),a(:,4));
hold off
colormap copper