Manual of Lua-OOCairo: pattern

lua-oocairo-pattern - Cairo pattern objects

Introduction

A pattern object is any one of several things that can be used as the source for a Cairo context, defining what colours and transparencies will be used for drawing. These objects can be created explicitly with the various pattern_create_* functions in the module table (see lua-oocairo(3) for details), or implicitly by calling methods like cr:set_source_rgb() on a context object (see lua-oocairo-context(3)).

Pattern objects can be compared with the == operator. This will compare the identity of the objects, so different Lua objects which refer to the same cairo_pattern_t will compare as equal.

Methods

pat:add_color_stop_rgb (offset, r, g, b)

Add a new colour stop to a gradient (either linear or radial, it doesn't matter). The offset is a number from zero (the start of the line or the first circle of the gradient) to one (the end of the line or the second circle). The colour values must also be numbers from zero to one. The alpha level is set to fully transparent.

This will throw an exception if called on a pattern which isn't a gradient.

pat:add_color_stop_rgba (offset, r, g, b, a)

Same as pat:add_color_stop_rgb() above, but the alpha value can be set to less than one to give some transparency to the gradient. This can be used for gradients which fade away into nothing for example.

pat:get_color_stops ()

Returns the color stops defined on a linear or radial gradient. Throws an exception if called on any other type of pattern.

The return value will be a table, an array with one entry per color stop. Each entry will be a table containing five numbers, in the following order: offset, red, green, blue, alpha.

pat:get_extend ()

Return the current method of extending the pattern beyond its limits. The return value will be one of the strings accepted by the pat:set_extend() method.

pat:get_filter ()

Return the current filter method, which will be one of the strings accepted by the pat:set_filter() method.

pat:get_linear_points ()

Return the start and end points of a linear gradient as four numbers. Throws an exception if called on any other type of pattern.

pat:get_matrix ()

Return the current transformation matrix used for the pattern. See lua-oocairo-matrix(3).

pat:get_radial_circles ()

Return the start and end circles of a radial gradient as six numbers. Throws an exception if called on any other type of pattern.

pat:get_rgba ()

Return the colour value and alpha level for a solid colour pattern. Throws an exception for any other type of pattern. The return values will be four numbers, in the following order: red, green, blue, alpha.

pat:get_surface ()

Return the surface object (see lua-oocairo-surface(3)) used for a surface pattern. Throws an exception for any other kind of pattern.

pat:get_type ()

Returns a string indicating what kind of pattern object this is. The return value will be one of the following:

  • linear

  • radial

  • solid

  • surface

pat:set_extend (extendtype)

Set the way in which the pattern should be extended beyond its defined limits. The argument must be one of the following strings:

none

Everything outside the area defined by the pattern is fully transparent.

repeat

Pattern tiled by endlessly repeating it.

reflect

Pattern tiled by reflecting it at its edges.

pad

Whatever is at the edge of the pattern is extended outwards.

pat:set_filter (filtertype)

Set the filter method used for picking colours from the pattern when it is being used to render something. The argument must be one of the following strings:

fast

Fast interpolation that is likely to be low quality in some cases (but probably OK for a smooth gradient).

good

Reasonably good quality interpolation.

best

The highest quality interpolation available, but likely very slow.

nearest

Pick colour of nearest pixel.

bilinear

Interpolate between pixels.

gaussian

Gaussian blur, but this isn't implemented yet.

pat:set_matrix (matrix)

Set the transformation matrix used for the pattern, as a table of six numbers. See lua-oocairo-matrix(3).