NAME

Prima::Drawable::Path - stroke and fill complex paths

DESCRIPTION

The module augments the Prima::Drawable's drawing and plotting functionality by implementing paths that allow arbitrary combinations of polylines, splines, and arcs, to be used for drawing or clipping shapes.

SYNOPSIS

# draws an elliptic spiral
my ( $d1, $dx ) = ( 0.8, 0.05 );
$canvas-> new_path->
	rotate(45)->
	translate(200, 100)->
	scale(200, 100)->
	arc( 0, 0, $d1 + $dx * 0, $d1 + $dx * 1, 0, 90)->
	arc( 0, 0, $d1 + $dx * 2, $d1 + $dx * 1, 90, 180)->
	arc( 0, 0, $d1 + $dx * 2, $d1 + $dx * 3, 180, 270)->
	arc( 0, 0, $d1 + $dx * 4, $d1 + $dx * 3, 270, 360)->
stroke;

API

Primitives

All primitives come in two versions, with absolute and relative coordinates. The absolute version draws a graphic primitive so that its starting point (or a reference point) is at (0,0). The relative version, called with an 'r' (f.ex. line vs rline) has its starting point as the ending point of the previous primitive (or (0,0) if there's none).

arc CENTER_X, CENTER_Y, DIAMETER_X, DIAMETER_Y, ANGLE_START, ANGLE_END, TILT = 0

Adds an elliptic arc to the path. The arc is centered around the (CENTER_X,CENTER_Y) point.

Important: if the intention is an immediate rendering, especially with a 1-pixel line width, consider decreasing diameters by 1. This is because all arc calculations are made with the floating point precision, where the diameter is also given not in pixels but in geometrical coordinates, to allow for matrix transformations. Before rendering is performed, arcs are transformed into spline vertices and then the transformation matrix is applied, and by that time the notion of an arc diameter is lost to be successfully converted into pixel size minus one.

Read more about this in "Antialiasing and alpha" in Prima::Drawable .

close, open

Closes the current shape and opens a new one. close() is the same as open() but makes sure the shape's first point is equal to its last point.

circular_arc ANGLE_START, ANGLE_END

Adds a circular arc to the path. Note that adding transformations will effectively make it into an elliptic arc, which is used internally by arc and rarc.

chord CENTER_X, CENTER_Y, DIAMETER_X, DIAMETER_Y, ANGLE_START, ANGLE_END.

Adds a chord to the path. Is there only for compatibility with Prima::Drawable.

ellipse CENTER_X, CENTER_Y, DIAMETER_X, DIAMETER_Y = DIAMETER_X, TILT = 0

Adds a full ellipse to the path.

glyph INDEX, %OPTIONS

Adds a glyph outline to the path. %OPTIONS are passed as is to "renger_glyph" in Prima::Drawable, except the fill option.

Note that filled glyphs require fillMode without the fm::Overlay bit set, and also the fill option set to generate proper shapes with holes.

line, rline @POINTS

Adds a polyline to the path

lines [X1, Y1, X2, Y2]..

Adds a set of multiple, unconnected lines to the path. Is there only for compatibility with Prima::Drawable.

moveto, rmoveto X, Y

Stops plotting the current shape and moves the plotting position to X, Y.

rarc DIAMETER_X, DIAMETER_Y, ANGLE_START, ANGLE_END, TILT = 0

Adds an elliptic arc to the path so that the first point of the arc starts on the last point of the previous primitive, or (0,0) if there's none.

rectangle X1, Y1, X2, Y2

Adds a rectangle to the path. Is there only for compatibility with Prima::Drawable.

round_rect X1, Y1, X2, Y2, MAX_DIAMETER

Adds a round rectangle to the path.

sector CENTER_X, CENTER_Y, DIAMETER_X, DIAMETER_Y, ANGLE_START, ANGLE_END

Adds a sector to the path. Is there only for compatibility with Prima::Drawable.

spline, rspline $POINTS, %OPTIONS.

Adds a B-spline to the path. See "spline" in Prima::Drawable for %OPTIONS descriptions.

text TEXT, %OPTIONS

Adds TEXT to the path. %OPTIONS are the same as in "render_glyph" in Prima::Drawable, except that unicode is deduced automatically based on whether the TEXT has utf8 bit on or off. An extra option cache with a hash can be used to speed up the function with subsequent calls. The baseline option is the same as "textOutBaseline" in Prima::Drawable.

Note that filled glyphs require fillMode without the fm::Overlay bit set, and also the fill option set to generate proper shapes with holes.

Transformations

Transformation calls change the current path properties (matrix etc) so that all subsequent calls would use them until a call to restore is made. The save and restore methods implement the stacking mechanism so that local transformations can be made.

Properties

canvas DRAWABLE

Provides access to the attached drawable object

matrix A, B, C, D, Tx, Ty

Applies a transformation matrix to the path. The matrix, as used by the module, is formed as follows:

A  B  0
C  D  0
Tx Ty 1

When applied to 2D coordinates, the transformed coordinates are calculated as

X' = AX + CY + Tx
Y' = BX + DY + Ty

precision INTEGER

Selects current precision for splines and arcs. See "spline" in Prima::Drawable, precision entry.

restore

Pops the stack entry and replaces the current matrix and graphic properties with it.

rotate ANGLE

Adds rotation to the current matrix

save

Saves the current matrix and graphic properties on the stack.

shear X, Y = X

Adds shearing to the current matrix

scale X, Y = X

Adds scaling to the current matrix

subpixel BOOLEAN

Turns on and off slow but more precise floating-point calculation mode

Default: depends on the canvas antialiasing mode

translate X, Y = X

Adds an offset to the current matrix

Operations

These methods perform path rendering and create an array of points that can be used for drawing

clip %options

Returns a 1-bit image with the clipping mask created from the path. %options can be used to pass the fillMode property that affects the result of the filled shape.

contours

Same as points but further reduces lines into a set of 8-connected points, suitable to be traced pixel-by-pixel.

extents

Returns two points that box the path.

last_matrix

Returns the current transform matrix (CTM) after running all commands

fill fillMode=undef

Paints a filled shape over the path. If fillMode is set, it is used instead of the one selected on the canvas.

fill_stroke fillMode=undef

Paints a filled shape over the path with the background color. If fillMode is set, it is used instead of the one selected on the canvas. Thereafter, draws a polyline over the path.

flatten PRESCALE

Returns new objects where arcs are flattened into lines. The lines are rasterized with a scaling factor that is as close as possible to the device pixels, to be suitable for a call to the polyline() method. If the PRESCALE factor is set, it is used instead to premultiply coordinates of arc anchor points used to render the lines.

points

Runs all accumulated commands, returns rendered set of points suitable for the Prima::Drawable::polyline and Prima::Drawable::fillpoly methods.

region MODE=fm::Winding|fm::Overlay, RGNOP=rgnop::Union

Creates a region object from the path. If MODE is set, applies fill mode (see "fillMode" in Prima::Drawable for more); if RGNOP is set, applies region set operation (see "combine" in Prima::Region).

stroke

Draws a polyline over the path

widen %OPTIONS

Expands the path into a new path object containing outlines of the original path as if drawn with selected line properties. The values of lineWidth, lineEnd, lineJoin, and linePattern are read from %OPTIONS, or from the attached canvas when available. Supports the miterLimit option with values from 0 to 20.

Note: if the intention is to immediately render lines, decrease lineWidth by 1 (they are 1 pixel wider because paths are built around the assumption that pixel size is 0, which makes them scalable).

Methods for custom primitives

append PATH

Copies all commands from another PATH object. The PATH object doesn't need to have balanced stacking brackets save and restore, and can be viewed as a macro.

identity

Returns the identity matrix

matrix_apply @POINTS

Applies the CTM to POINTS, returns the transformed points. If @POINTS is a list, returns the transformed points as a list; if it is an array reference, returns an array reference.

AUTHOR

Dmitry Karasik, <dmitry@karasik.eu.org>.

SEE ALSO

Prima::Drawable