decrease image size in databound

hi!
   i am using datagrid to display images. when i click insert button image is insert into datadase and also databind image is displayed in datagrid.its working.
 but my aim is when i retrive the data, image dimensions is changed to 100*100. i give height and width of image control.but image size is take to original size and control size is 100*100.
my doubt is it display total image is 100*100
any code to do this. using itemtemplate we decrease image size?
thanks