Trim and find position of result with rmagick

Question

I'm working on a jigsaw puzzle webapp, and one of the requirements is automatically generating puzzle pieces from any image. I'm using RMagick for the image processing. I've got some sets of blank puzzle pieces to use as masks, and I can handle that part, but then I need to trim the whitespace (er, transparentspace) out of the resulting images.

Now, I know I can use trim for this - I might have to put a one-pixel border on it to make sure all four corners are the right color, but that's easy and I can just subtract one pixel from the final number. The only problem is that I also need to record the position of the piece. According to the documentation on trim, the function will "retain the offset information", which sounds like exactly what I need. But I can't find anything about how to retrieve the offset information! Does anyone know how to do that?

If worst comes to worst, I suppose I could always just look through pixel-by-pixel, find the boundaries myself, and use crop to trim the picture, but that wouldn't exactly be good for performance.

Answer 1

Aha, found it. image.page.x and image.page.y give the upper left corner, and then image.rows and image.columns have the height and width.