The extended RDIB format, designed to incorporate enhancements such as impression, is defined as follows:
<RDIB-form>
RIFF('RDIB'
<bmhd-ck> /* Bitmap header chunk */
[ <pal-file> | /* Internal palette chunk */
<XPAL-ck> ] /* External palette chunk */
<bitmap-data> ) /* Bitmap data */
The <pal-file> chunk can be any of the palette-file formats described in Palette File Format. The <bmhd-ck>, <XPAL-chunk>, and <bitmap-data> are described in the following sections.