rebol-agg

Rebol-AGG CI Gitter Zulip

AGG (Anti-Grain Geometry) extension for Rebol3 (version 3.14.1 and higher)
(This is still work in progress!)

agg: import agg
img: agg/draw 600x600 [pen red line-width 5 triangle 0x0 600x600 300x600]
save %temp.png img

Draws scalable vector graphics to an image

• image [image! pair!]
• commands [block!]

The AGG Draw dialect provides comprehensive 2D vector graphics capabilities through Rebol's block-based syntax. Each command configures state or immediately renders geometry with flexible coordinate input.

Sets fill color or toggles filling for subsequent path rendering. Supports solid colors and linear gradients.

Parameters:

Example:

fill 255.128.0.255 ; Semi-transparent orange fill
fill false ; Disable filling

Sets stroke color or toggles stroking for path outlines.

Parameters:

Example:

pen 0.0.255.255 ; Blue stroke
pen false ; No outline

Sets stroke thickness for subsequent paths.

Parameters:

Example:

line-width 3.0

Controls corner join style between path segments.

Parameters:

Defines appearance of path endpoints.

Parameters:

Global transparency multiplier for all operations.

Parameters:

Controls anti-aliasing and gamma correction.

Parameters:

Size for subsequent point drawing commands.

Parameters:

Sets Porter-Duff/SVG compositing mode.

Modes: 'clear, 'source-copy, 'source-over, 'destination-over, 'source-in, 'destination-in, 'source-out, 'destination-out, 'source-atop, 'destination-atop, 'xor, 'add, 'multiply, 'screen, 'overlay, 'darken, 'lighten, 'color-dodge, 'color-burn, 'hard-light, 'soft-light, 'difference, 'exclusion

Draws open polyline (stroke only) from point sequence.

Parameters (coords):

Example:

line 10x10 50x20 80x40 120x10

Renders closed polygon from vertices.

Parameters (coords):

Renders one or more triangles from vertex triplets.

Parameters (coords):

Draws points using current point-size.

Parameters (coords):

Draws rectangle (optionally rounded).

Parameters:

Draws ellipse/circle by center and radii.

Parameters:

Ellipse from bounding rectangle.

Parameters:

Elliptical arc with closure options.

Parameters:

Cubic Bézier spline segments.

Parameters:

Example:

cubic 10x10 30x50 70x50 90x10

Shifts coordinate origin.

Parameters: offset pair! (dx, dy)

Scales coordinate system.

Parameters: number! (uniform) or pair! (sx, sy)

Applies shear transformation.

Parameters: angles pair!/number!, optional pivot pair!

Rotates around center.

Parameters: angle number! (degrees), optional center pair!

Compound affine transform.

Parameters: center pair! (opt), then rotate/scale-x/scale-y/translate

Full 2D affine matrix.

Parameters: vector!/block! (6 values: sx shy shx sy tx ty)

Returns identity transform.

Rectangular clipping region.

Parameters: top-left pair!, bottom-right pair!

Clears entire surface to transparent black.

Clears clip region (optional fill color).

Parameters: tuple! color or unset! (transparent)

State isolation context.

Parameters: block! of drawing commands

Example:

push [pen red line 10x10 100x100]
; Original pen restored

Loads font resource.

Parameters: file! path or string! name

Renders text string.

Parameters:

Renders complex path from sub-dialect.

Parameters: path-data block! with path commands (move, line, arc, curve, close, etc.)

Blits image with optional scaling.

Parameters:

The AGG Path DSL defines a sub-dialect for constructing complex vector paths within the shape command of the draw dialect. Paths are built sequentially from a current "pen" position, supporting absolute and relative coordinates for maximum flexibility.

Paths support filling, stroking, or both based on the outer draw state's fill/pen settings. Multiple subpaths can be defined before closing.

Moves the path pen to an absolute position (starts new subpath).

Parameters:

Example:

shape [move 10x10 ...]

Moves pen by relative offset (starts new subpath).

Parameters:

Adds one or more absolute line segments from current position.

Parameters:

Example:

shape [move 0x0 line 50x0 50x50 0x50]

Adds relative line segments.

Parameters:

Horizontal line to absolute X (Y unchanged).

Parameters: x number!

Horizontal relative delta X.

Parameters: dx number!

Vertical line to absolute Y (X unchanged).

Parameters: y number!

Vertical relative delta Y.

Parameters: dy number!

Adds elliptical arc (SVG-style parameters).

Parameters:

Relative endpoint version.

Parameters:

Absolute cubic Bézier (C1, C2, end).

Parameters:

Example:

shape [move 10x10 curve 30x50 70x50 90x10]

All-relative cubic Bézier.

Parameters: Relative control1, control2, end-delta pair!

Smooth cubic (first control relative/reflected).

Parameters: control1 pair! (relative), end-point pair!

Fully relative smooth cubic.

Parameters: control1 pair! (relative), end-delta pair!

Absolute quadratic Bézier (single control).

Parameters:

Relative quadratic.

Parameters: Relative control, end-delta pair!

Smooth quadratic (reflected control).

Parameters: control pair! (relative/reflected)

Relative smooth quadratic.

Parameters: end-delta pair!

Closes current subpath to its starting point with a straight line.

Parameters: None

Example (Closed Rectangle with Curve):

shape [
 move 10x10
 line 90x10 90x50 10x50
 curv 30x30 50x70
 close
]

Usage in Draw: Paths are consumed by shape in the main draw dialect, inheriting fill/pen state. All commands support batching multiple segments for efficiency.