is a graphics directive that specifies that graphical objects that follow are to be displayed, if possible, with opacity a.
uses the specified color with opacity a.
- Opacity runs from 0 to 1, with 0 representing perfect transparency.
- If an opacity-a object with color c1 is placed in front of an object with color c2, the resulting color will be the blend ac1+(1-a)c2.
- If red and blue with opacity 0.5 are combined, the result is purple—not black, as it would be with physical monochromatic filters. »
- Opacity works in both 2D and 3D graphics.
- It may take significantly longer to render 3D graphics that involve transparent surfaces.
- Graphics that involve transparency may need to be printed as high‐resolution bitmaps.
- On many computer systems, objects with opacity a will appear completely transparent if a is too small. »