Why does an image in Impress revert its transparency?

I’m using the TexMaths plugin for Impress to make nice equations using Latex. The plugin generates an image of the equaiton. The image is generated with a default transparency gradient of “Linear,” which is irritating, but can easily be corrected to “None.” However, after saving and reopening the file, the images that were created with the TexMaths plugin have their transparencies reverted back to “Linear,” which is, well, wrong.

Is it possible to fix this? I don’t know if the problem lies with Impress or the plugin or somewhere else.