how do i delete photos from my iphone 4 iOS 7?

I updated my iphone 4 to iOS7 today and I'm not able to delete photos from my iphone. On the iphone I can select photos but the garbage can is grayed out. I just want to delete all photos to make space on the iphone but i wan the pics saved onto my mac. I've imported them from the iphone to my mac so I should not be able to delete them. After importing it asked if I wanted to delete them and I thought I selected Yes.