Document Express Enterprise encodes the following types of DjVu® documents:
Photo DjVu documents are created from scanned images that contain color or grayscale photographs, paintings, and other continuous-tone images. Document Express Enterprise encodes these images using the IW44 wavelet-based compression method because they are typically smooth and can be displayed at a low resolution without adverse affects on their visual quality.
To create a photo DjVu document, use the phototodjvu command.
Bitonal DjVu documents are created from scanned images that contain black and white text and simple line drawings. Document Express Enterprise encodes bitonal images using the JB2 data compression method.
Examples of bitonal images include:
To create a bitonal DjVu document, use the phototodjvu command (for images that contain just photographs).
Color DjVu documents are created from high-resolution color or grayscale scanned images that contain both pictures and text. Document Express Enterprise segments color images into multiple layers and then encodes each layer using the appropriate JB2 data compression or IW44 wavelet-based compression method.
For more information about the layers of a color document, see Segmentation Process.
Color images contain one or more of the following elements:
Examples of color images include:
To create a color DjVu document, use the bitonal profiles.
NOTE: Document Express Enterprise encodes grayscale images as color, not black and white.