Transparency and blending

<BlendingSetting> sets how much of an object shows (Opacity) and how its colours combine with what is beneath (BlendMode).

In short Opacity is a percentage, 100 fully opaque. BlendMode is one of InDesign's blend modes, Normal unless set. On a group, IsolateBlending keeps the members' blend modes from reaching below the group and KnockoutGroup stops members from showing through each other. The setting sits in one of four containers: TransparencySetting for the whole object, or FillTransparencySetting, StrokeTransparencySetting or ContentTransparencySetting for one part of it.

<BlendingSetting>

Attribute · BlendingSetting	Values	Paged	paged.set
BlendMode	Normal | Multiply | Screen | Overlay | SoftLight | HardLight | ColorDodge | ColorBurn | Darken | Lighten | Difference | Exclusion | Hue | Saturation | Color | Luminosity	read · written	frameBlendMode
Opacity	number (percent)	read · written	frameOpacity
IsolateBlending	false	not read
KnockoutGroup	false	not read

InDesign's default, as its preferences write it: BlendMode="Normal" Opacity="100" KnockoutGroup="false" IsolateBlending="false".

Opacity

A percentage from 0 (invisible) to 100 (opaque), written as a whole number in the surveyed files. At the object level it fades everything the object draws together: fill, stroke, content and effects. Opacity is not a tint: a 50 % tint is a lighter colour that still covers what is beneath; 50 % opacity lets it show through.

BlendMode

How the object's colours combine with the colours beneath it. The surveyed documents use Normal, Multiply, Screen, Overlay, SoftLight, Darken, Lighten and ColorBurn, Multiply most often after Normal. A blend mode affects everything beneath the object down to the page, unless a group isolates it.

Blending happens in the document's blending space, BlendingSpace on the <TransparencyPreference> in Preferences.xml: CMYK in nearly every surveyed file.

IsolateBlending and KnockoutGroup

Both matter on a group:

• IsolateBlending="true": the members' blend modes combine only with each other, not with what lies beneath the group.
• KnockoutGroup="true": members do not show through one another; each member blends only with what is beneath the group.

Both are false in every surveyed file.

The four levels

The same <BlendingSetting> can sit in four containers, written as children of the page item after its <Properties>:

A rectangle with a 30 % fill opacity and a fully opaque stroke is written as FillTransparencySetting with Opacity="30", while the object level stays at 100. Object-level opacity multiplies with each part's own.

Groups

A <Group>'s TransparencySetting treats the group as one: its members are composed first, and the result is faded or blended as a whole. Three overlapping 50 %-opaque shapes look different from the same shapes in a 50 %-opaque group: in the group they do not show through each other.

In Paged: object-level Opacity and BlendMode are applied to rectangles, ovals, polygons, text frames and groups; a group is composed as a unit. Paged also reads HardLight, ColorDodge, Difference, Exclusion, Hue, Saturation, Color and Luminosity. Opacity and blend mode on a graphic line are not applied yet, and IsolateBlending and KnockoutGroup are not read. The fill, stroke and content levels are not kept apart: an opacity or blend mode found there is applied to the whole object.

Supported · verified Supported · verified Parsed, partly rendered

Frequently asked questions

How do I make an object 50 % transparent in IDML? Give it <TransparencySetting><BlendingSetting Opacity="50"/></TransparencySetting> after its <Properties>.

What blend modes appear in real files? Normal, then Multiply, and also Screen, Overlay, SoftLight, Darken, Lighten and ColorBurn in the surveyed documents.

How do I fade only the fill and keep the stroke opaque? Put the BlendingSetting in FillTransparencySetting instead of TransparencySetting.

Is opacity on a group the same as opacity on each member? No. A group's opacity applies to the composed group, so its members do not show through one another.

What do IsolateBlending and KnockoutGroup do? On a group, IsolateBlending confines the members' blend modes to the group and KnockoutGroup keeps members from showing through each other.