Complete Communications Engineering

Color management is the process of maintaining consistent color among devices. The goal is to make colors look the same regardless of the platform, (hardware or software) used to capture, display or print images. Without color management, colors that should appear the same may appear significantly different.

Fig. 1 Standard color profiles support Color Management across different devices

Color Profiles

The International Color Consortium (ICC) defines a cross-platform standard for encoding color profiles. A color profile is a precise mapping between a given color space and an ICC standard color space, such as CIELAB. Every color-managed device requires a personalized color profile which characterizes the device’s color response. Colors from the input device are transformed into a standard color profile. Then, colors from the standard profile are converted into the output device’s color profile. There are a number of different color profile types. Three common types are: scanner profiles, monitor profiles and printer profiles.

A color transformation is a set of conversions from one color space to another. Color matching is an algorithm that adjusts the numerical values related to different devices by color transformation the way that the perceived color for human eye they produce remains consistent. There is no common method for color matching, and the performance depends on the capability of each particular method.

A color gamut is a range of colors that a device can accommodate (capture, display, or print). Each device has its own color gamut that varies in range, which may make an accurate reproduction impossible. Therefore, some devices need some color rearrangement near the borders of the gamut. Some colors must be shifted inside the gamut, otherwise they cannot be represented on the output device.

For example, RGB color space has a wider gamut range than CMYK color space. After an RGB to CMYK conversion, some colors may be lost (such as highly saturated magenta).

For neutral colors, correct adjustment is very important. The adjustment can be based on gray balance, neutral balance, or white balance. White balance is especially important for color management. Color balancing refers to the process of removing an overall color bias from an image. For example, if an image appears too red, it is said to have a red cast. Removing this red cast brings the image back into balance.

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