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           SECTION 4.6                                                                      Patterns



           By setting a shading pattern as the current color in the graphics state, a PDF con-
           tent stream can use it with painting operators such as f (fill), S (stroke), Tj (show
           text), or Do (paint external object) with an image mask to paint a path, character
           glyph, or mask with a smooth color transition. When a shading is used in this
           way, the geometry of the gradient fill is independent of that of the object being
           painted.


           Shading Operator

           When the area to be painted is a relatively simple shape whose geometry is the
           same as that of the gradient fill itself, the sh operator can be used instead of the
           usual painting operators. sh accepts a shading dictionary as an operand and
           applies the corresponding gradient fill directly to current user space. This opera-
           tor does not require the creation of a pattern dictionary or a path and works with-
           out reference to the current color in the graphics state. Table 4.27 describes the sh
           operator.

           Note: Patterns defined by type 2 pattern dictionaries do not tile. To create a tiling
           pattern containing a gradient fill, invoke the sh operator from within the content
           stream of a type 1 (tiling) pattern.

                                       TABLE 4.27 Shading operator
OPERANDS      OPERATOR     DESCRIPTION

name          sh           (PDF 1.3) Paint the shape and color shading described by a shading dictionary, sub-
                           ject to the current clipping path. The current color in the graphics state is neither
                           used nor altered. The effect is different from that of painting a path using a shading
                           pattern as the current color.
                           name is the name of a shading dictionary resource in the Shading subdictionary of
                           the current resource dictionary (see Section 3.7.2, “Resource Dictionaries”). All co-
                           ordinates in the shading dictionary are interpreted relative to the current user
                           space. (By contrast, when a shading dictionary is used in a type 2 pattern, the
                           coordinates are expressed in pattern space.) All colors are interpreted in the color
                           space identified by the shading dictionary’s ColorSpace entry (see Table 4.28). The
                           Background entry, if present, is ignored.

                           This operator should be applied only to bounded or geometrically defined shad-
                           ings. If applied to an unbounded shading, it paints the shading’s gradient fill across
                           the entire clipping region, which may be time-consuming.

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