Normalizing Colors

A PDF can contain elements and images in multiple color spaces. Before the conversion to the target color space, colors can be normalized to the same color space.

• Normalizing is applied to images that are not already in the target color space. Normalizing can mean a separation from RGB to CMYK or a CMYK to CMYK conversion from the current CMYK color space to the input color space for the following conversion step.
   
• Normalizing can be based on DeviceLink MX profiles or on standard ICC profiles.
   
• Normalizing settings can be defined separately for images and vector objects.
   

If normalizing is not used for an input color space, for example for RGB, or for the whole PDF, objects in the "wrong" color space will not be color managed. For example, if you have defined a hotfolder with a CMYK-to-CMYK conversion profile and without normalizing, all RGB objects will not be processed.

If flattening is used, RGB objects overlapping with CMYK objects will be resolved. Therefore, RGB objects need to be normalized and images and vector objects need to use the same normalization settings.

ICC versus MX Normalization:
You can either use ICC based color management or define rules for replacing ICC with MX profiles (ICC Replacement Rules). To ensure a fail-safe conversion, you can automatically apply different MX profiles according to the embedded ICC profile of the PDF object / output ICC defined in the hotfolder.

A DeviceLink profile such as an MX4 profile has been specifically designed for a color transformation from a defined input color space to a defined output color space. As the profile is created for one specific combination of an input and output device, the color transformation generally provides a very high quality. Information on the black channel is maintained during the transformation.

In contrast, standard ICC profiles use a device-independent intermediate color space, usually Lab, to link two device-dependent color spaces. In other words, standard ICC profiles are device independent. Two ICC profiles must be combined with each other to convert one color space to another. Information on the black channel is lost due to the use of the intermediate Lab space.