What is the method used to obtain the effect where a user selects an item from your online store, and upon checkout can engrave the product and view a preview before putting their order in, are the letters they enter engraved by having an image for each letter, then copying them onto a picture of the product?
using a convolver, the engraving of the text can be performed ~dynamically.. based on the font used to write the text.. You'd still have to alphablit the resulting image over whatever the thing it's supposed to be over though.. as a convolver will process an entire image...
So you're saying just write text to the image and try to make it look like it's engraved.. would it be feasible to place an image of each letter, taken from a sample engraving?
unless it's a small pool of fonts, I'd suggest doing it dynamically.. if the font is loadable from php.. a convolver is a math matrix like routine that performs math on neighboring pixels to get a new current pixel.. basically..