image doesn't display in item and website

Hi, I just began to use omeka this week. The problem is when I upload images into item, they don't show up in thumbnail or website. If I click on image's title or the icon that image will be opened in a new page. I checked the imagemagick directory path (/Applications/MAMP/Library/lib/ImageMagick/bin) and it works. Can you help me solve the problem? Thanks!