Image Rendering enforces a two Megapixel size limitation for non-pyramid vignettes.
Modify the value of
IrMaxNonPyrVignetteSize in install_root /ImageServing/conf /ImageServerRegistry.conf if your application requires support for non-pyramid vignettes with an image area (width x height) larger than this limit.
IS::MaxMessageSize may also need to be adjusted to allow unusually large response image sizes. Refer to the Image Serving documentation for details.