ImageMagick Php Thumbs + Gallery Application

We need a php application to deal with image and create specific gallery with titles to be included in some pages and image need to be resized to create thumbs and thumbs need to be perfect and centered and cached not created on the fly each time the page load. All picture are on white background but they dont have the same size and may not be centered correctly. The php application need to center the object in the white background before creating the thumb.