PDF Optimizer

Color Conversion

Optional. Enable this value by adding it to the profile and setting it equal to ON.

We can see thousands of different shades of colors, and high-quality digital cameras and scanners can often detect millions of shades. To manage the broad range of colors for producing graphics images in digital content, imaging professionals have developed models to define these colors, called color spaces.

Many color spaces have been defined. Some are dependent on hardware devices, and define what a camera can detect, or a printer print, or a monitor display. Others are based on software and thus can be used across many different types of devices, such as Adobe RGB or sRGB (standard RGB). A color space must be defined for any device or software product to make sure that coloring patterns remain the same from one device or system to another.

The Standard RGB color space, sRGB, was developed by Microsoft and Hewlett Packard to describe colors available on most monitors and displays. This color space is also commonly used for web graphics.

Adobe Systems’ own Adobe RGB (Red/Green/Blue) color space is designed to hold all of the colors that are likely to be available on any color CMYK (Cyan/Magenta/Yellow/Black) printer. It is considerably larger than Standard RGB.

Color profiles are standards for managing colors, used to ensure that the colors for text or graphics in a file remain the same regardless of the hardware or software used to display, edit, or print that file. Color profiles are based on the specification created by the International Color Consortium (ICC) in 1993 to govern color and color management across all operating systems, platforms, and software and hardware and software systems. A color profile is usually expressed as a file (*.icc) included in the software or driver for an installed printer, scanner or other hardware device, or in software used to edit a file that is to be displayed or printed. A profile provides a set of data that describes an input or output device. An .icc color profile file can also be embedded in a PDF document.

enabled Enables PDF Optimizer to convert colors in a PDF document using a target profile. Defaults to OFF.
convert-profile The profile used to convert colors in the PDF document.
lab-d50 L*a*b color specification with a D50 white point. The Lab color space is based on the CIE XYZ color space, but it includes a dimension L, for lightness, along with a and b coordinates, to define the color. This is Adobe Systems’ standard Lab profile.
srgb Standard RGB, the default profile for Windows monitors.
apple-rgb Apple RGB, the default profile for Mac monitors
color-match-rgb Color Match RGB. This is a simpler version of the Radius ColorMatch RGB space, without the non-zero black point.
gamma-18 Gray Gamma 1.8, grayscale display profile, used for content viewed on a monitor.
gamma-22 Gray Gamma 2.2
dot-gain-10 Grayscale printer profile, with dot gain 10%. Dot gain is commonly used in offset printing to define the increase in size in halftone dots in the printing process, making a printed document look darker than intended.
dot-gain-15 Dot gain 15%
dot-gain-20 Dot gain 20%
dot-gain-25 Dot gain 25%
dot-gain-30 Dot gain 30%
monitor-rgb RGB Monitor, referring to a monitor that requires separate signals for the three primary colors.
acrobat5-cmyk Adobe Reader 5 CMYK
acrobat9-cmyk Adobe Reader 9 CMYK
color-convert-action The type of color conversion. The values available include convert and decalibrate. The default value is convert. The decalibrate setting means that the system will decalibrate calibrated color spaces in the PDF document.

If a color profile (.icc file) is assigned to a PDF document, or to a feature of that PDF document, such as an image, the document or image is referred to as “calibrated.”

convert-intent Use this setting to specify the color translation method for colors that are outside the gamut of the color profile.  The intent lets the software determine how to substitute a color that can be written to the file.  You can select from a list of standard strategies to apply when converting the colors in that original PDF document.

The conversion intent is used to describe how the destination device for the document reproduces the colors in the document. Thus, when you print or display the PDF output file, the colors in the output file will match as closely as possible the original color found in the source PDF document.

perceptual-intent Default value. Generally used for photography. This method does not map colors one for one but estimates to match colors. Hence it often provides the most pleasing result but not necessarily the most accurate.
relative-colorimetric-intent Generally used for photography. The relative method uses an algorithm to select the closest possible color map to be true to the specified color.
saturation-intent Commonly used in charts and diagrams with a limited palette of colors where hue is not as important.
absolute-colorimetric-intent Often used to select a specific color or set of colors for drawings or designs. Absolute serves to reproduce the exact colors provided in the original PDF document. A common reason for using absolute would be to reproduce the color used in a corporate logo such as IBM Blue. The color is changed by selecting a defined match. This method does not use a conversion algorithm to select the closest color available.
profile-intent If you specify a color profile in the convert-profile option the intent value defaults to that profile. In that case software will use the rendering intent provided with the ICC color profile currently in use for that PDF document.  For example, the Adobe RGB 1998 color profile uses Relative Colormetric as its rendering intent. So if you specify Adobe RGB 1998 (srgb) as the color profile, and profile-intent is selected here, the PDF Optimizer software will use relative.