Mask an image with another image

InDesign doesn't have a specific Mask command, but you can still combine two images to create unique graphics. The secret is in the Clipping Path command. You can't actually use clipping paths to mask images in InDesign, but you can use paths created in InDesign or embedded alpha channels created in an image-editing application. The Clipping Path command allows you to both create and control these types of paths.

To mask an image with an InDesign path, place the image you plan to use as a mask into your document. Next, select Clipping Path from the Object menu to display the Clipping Path dialog box. Choose Detect Edges from the Type pop-up menu. Then, click OK. Finally, click on the image with the Direct Selection tool and use the Place command to import the second image into the selected path.

To mask an image with the alpha channel of another image, select the Show Import Options check box as you place the image you plan to use as a mask and click Open. In the resulting dialog box, choose the embedded channel from the Alpha Channel pop-up menu. Click OK and click the loaded icon on the page to import the file into your document. Now, while the object is selected, choose Clipping Path from the Object menu. In the Clipping Path dialog box, select Alpha Channel from the Type pop-up menu and select the embedded alpha channel from the Alpha pop-up menu. Then, click OK. Finally, select the image with the Direct Selection tool and place the second image into the selected path.