Conversion of indd files to png file format

Adobe InDesign offers default support for export to several graphics, including JPEG. You can select any element in .indd document and with the File ► Export function save it as a .jpg image. Plenty of settings and other options exists, so you can tweak the output image settings before you save it. Once you have the .jpg file, you can convert it to PNG with pretty much every graphics editor.

Open INDD file    Open PNG file