I have extended RGBImageFilter and implemented a GrayFilter. Passing this GrayFilter to FilteredImageSource along with an Image object representing an animated GIF image. When I render the output image, some of the image frames are not converted to gray scale and still appear in color.

This is reproducible on all platforms atleast since 1.4.2.

I have attached a sample test and the image for which the test has failed. Run the test passing the image file name as a command line argument. If you see some color frames in the gray scale image rendered, the bug is reproduced.