NAME
Prima::Drawable::Path  stroke and fill complex paths
DESCRIPTION
The module augments the Prima::Drawable
drawing and plotting functionality by implementing paths that allow arbitrary combination of polylines, splines, and arcs, to be used for drawing or clipping shapes.
SYNOPSIS
# draws elliptic spiral
my ( $d1, $dx ) = ( 0.8, 0.05 );
$canvas> new_path>
scale(200, 100)>
rotate(45)>
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 elliptic arc to path centered around (CENTER_X,CENTER_Y).
Important: if the intention is an immediate rendering, especially with 1pixel line width, consider decreasing diameters by 1. This is because all arc calculations are made with floating point, where diameter is also given not in pixels but in geometrical coordinates, to allow for matrix transformations. Before rendering is performed, arcs are tranformed into spline vertices and then 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.
 close, open

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

Adds circular arc to the path. Note that adding transformations will effectively make it into elliptic arc, which is used internally by
arc
andrarc
.  chord CENTER_X, CENTER_Y, DIAMETER_X, DIAMETER_Y, ANGLE_START, ANGLE_END.

Adds 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 full ellipse to the path.
 glyph INDEX, %OPTIONS

Adds glyph outline to the path.
%OPTIONS
are passed as is to "renger_glyph" in Prima::Drawable. Note that filled glyphs requirefillMode
without thefm::Overlay
bit set andfill
option set to generate proper shapes with holes.  line, rline @POINTS

Adds a polyline to path
 lines [X1, Y1, X2, Y2]..

Adds 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 elliptic arc to 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 rectangle to the path. Is there only for compatibility with
Prima::Drawable
.  sector CENTER_X, CENTER_Y, DIAMETER_X, DIAMETER_Y, ANGLE_START, ANGLE_END

Adds sector to the path. Is there only for compatibility with
Prima::Drawable
.  spline, rspline $POINTS, %OPTIONS.

Adds Bspline to path. See "spline" in Prima::Drawable for
%OPTIONS
descriptions.  text TEXT, %OPTIONS

Adds
TEXT
to the path.%OPTIONS
are same as in "render_glyph" in Prima::Drawable, except thatunicode
is deduced automatically based on whetherTEXT
has utf8 bit on or off; and an extra optioncache
with a hash can be used to speed up the function with subsequent calls.baseline
option is same as "textOutBaseline" in Prima::Drawable.
Properties
Transformations
Transformation calls change the current path properties (matrix etc) so that all subsequent calls will use them until a call to restore
is used. save
and restore
implement a stacking mechanism, so that local transformations can be made.
The final transformations calculate coordinates the new and the existing matrices:
P' = NewMatrix * P
 matrix A, B, C, D, Tx, Ty

Applies transformation matrix to the path. The matrix, as used by the module, is formed as such:
A B 0 C D 0 Tx Ty 1
and when applied to 2D coordinates, is 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

Duplicates the current matrix and graphic properties and pushes them to the stack.
 shear X, Y = X

Adds shearing to the current matrix
 scale X, Y = X

Adds scaling to the current matrix
 translate X, Y = X

Adds offset to the current matrix
Operations
These methods perform actual path rendering, that was delayed until that, and will create an array of points that can be used for actual drawing.
 clip %options

Returns 1bit image with clipping mask of the path.
%options
can be used to passfillMode
property that affects the result of the filled shape.  contours

Same as points but further reduces lines into a 8connected set of points, suitable to be traced pixelbypixel.
 extents

Returns 2 points that box the path.
 last_matrix

Return CTM resulted 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.  flatten PRESCALE

Returns new objects where arcs are flattened into lines. The lines are rasterized with scaling factor that is as close as possible to the device pixels, to be suitable for direct send to the polyline() API call. If PRESCALE factor is set, it is used instead to premultiply coordinates of arc anchor points used to render the lines.
 points FOR_FILL_POLY=0

Runs all accumulated commands, and returns rendered set of points, suitable for further calls to either
Prima::Drawable::polyline
orPrima::Drawable::fillpoly
depending on theFOR_FILL_POLY
flag.  region MODE=fm::Windingfm::Overlay, RGNOP=rgnop::Union

Creates a region object from polygonal shape. 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 path into a new path object containing outlines of the original path as if drawn with selected line properties.
lineWidth
,lineEnd
,lineJoin
,linePattern
are read from%OPTIONS
, or from the attached canvas when available. SupportsmiterLimit
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 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
andrestore
, and can be viewed as a macro.  identity

Returns identity matrix
 matrix_apply @POINTS

Applies current matrix to POINTS, returns the transformed points. If @POINTS is a list, returns list; if it is an array reference, returns array reference.
AUTHOR
Dmitry Karasik, <dmitry@karasik.eu.org>.