ICO201

ICO201: DuplicateFrameTypes

Each icon file contains some number of frames. A frame is a bitmap that is rendered at a particular size and color depth. For example, one ICO file might contain the same image, rendered at 16x16 and 32x32 pixel sizes.

Typically, applications just tell the graphics stack to pick the "best" icon for the current screen resolution and color depth. A typical graphics library would do this by skimming through the ICO file until it finds a frame of the correct dimensions and color depth. This means that a typical graphics stack will never have any use for multiple frames that have the same dimensions and color depth. The graphics stack will always pick the first frame that matches its criteria, and ignore the rest.

You will get this warning if there are multiple frames with the same dimensions and color depth. It's possible that this is intentional: an application might write some custom code to select frames by index, rather than just asking the graphics library to pick the "best" icon for the screen resolution and color depth. For example, an application might bundle several different Wi-Fi signal strength icons (📶) in the same ICO file, then select the one to draw based on the current signal strength.

But it's more likely that this is an oversight. If you didn't intend to include rendudant frames in the ICO file, you can use IcoCut to remove them. Otherwise, you are just wasting disk space.

You can use the IcoTools suite to create such an icon. For example, IcoCat can be used to append any number of frames to an ICO file.