The `set style fill` command is used to set the default style of the plot elements in plots with boxes, histograms, candlesticks and filledcurves. This default can be superseded by fillstyles attached to individual plots. See also 'set style rectangle'.
Syntax:
set style fill {empty
| {transparent} solid {<density>}
| {transparent} pattern {<n>}}
{border {<colorspec>} | noborder}
The default fillstyle is `empty`.
The `solid` option causes filling with a solid color, if the terminal supports that. The <density> parameter specifies the intensity of the fill color. At a <density> of 0.0, the box is empty, at <density> of 1.0, the inner area is of the same color as the current linetype. Some terminal types can vary the density continuously; others implement only a few levels of partial fill. If no <density> parameter is given, it defaults to 1.
The `pattern` option causes filling to be done with a fill pattern supplied by the terminal driver. The kind and number of available fill patterns depend on the terminal driver. If multiple datasets using filled boxes are plotted, the pattern cycles through all available pattern types, starting from pattern <n>, much as the line type cycles for multiple line plots.
The `empty` option causes filled boxes not to be filled. This is the default.
By default, border, the box is bounded by a solid line of the current linetype. `border <colorspec>` allows you to change the color of the border. `noborder` specifies that no bounding lines are drawn.
— SET STYLE FILL TRANSPARENT —
Some terminals support the attribute `transparent` for filled areas. In the case of transparent solid fill areas, the `density` parameter is interpreted as an alpha value; that is, density 0 is fully transparent, density 1 is fully opaque. In the case of transparent pattern fill, the background of the pattern is either fully transparent or fully opaque.
terminal solid pattern pm3d
--------------------------------
gif no yes no
jpeg yes no yes
pdf yes yes yes
png TrueColor index yes
post no yes no
svg yes no yes
wxt yes yes yes
x11 no yes no
Note that there may be additional limitations on the creation or viewing of graphs containing transparent fill areas. For example, the png terminal can only use transparent fill if the "truecolor" option is set. Some pdf viewers may not correctly display the fill areas even if they are correctly described in the pdf file. Ghostscript/gv does not correctly display pattern-fill areas even though actual PostScript printers generally have no problem.