Cutting a transparent image into a shape

[Manon303701964rmg]

Hi, I'm beginning with indesign, and I have an issue : I try to use an image with transparency to cut its shape into a rectangle. The problem is when I use pathfinder, it's cutting a rectangle, the whole image, and not just the non transparent part of the image. What am I missing? 

I tried to use the contour detection to cut the exact shape, but pathfinder is not allowed in that case.

Thanks for your help.

[Bill Silbert]

If you're dealing with a Photoshop image I would suggest doing the whole thing in Photoshop. If you're unfamiliar with the process then watch: https://www.youtube.com/watch?v=M9WO-vaKISI. If the image is from Illustrator then you can either do it within Illustrator or you can copy and paste the image from Illustrator to InDesign (not usually the recommended way to import Illustrator art but in this case it is appropriate). Take the pasted image select it and make it into a Compound Path (Object>Path>Make Compound Path). Make sure that the object is the top object above the rectangle you're using, select both the compound path and the rectangle and apply the Subtract Pathfinder option.