As discussed in the May community call, here are my notes on a general
canvas-like 2D API

# Notes on a general 2D API

## Introduction and Motivation

The principle is to keep the number of methods small and consistent,
using a common set of arguments for
location (x, y), and dimensions (w, h).

## Coordinate System

The coordinate system follows the traditional convention you learned in school:
x increasing to the left and y increasing from top to bottom. To
simplify, the coordinate system uses
percentages ranging from (0-100).

For example:

* (0,0) is the origin (lower left)
* (0,100) is the upper left
* (100,0) is the lower right
* (100, 100) is the lower right
* (50,50) is middle of the canvas

## Text

The text methods place text at any coordinate, where the Y is the baseline.
Text strings are Unicode, encoded in UTF-8.

Text attributes include:

* Font
* Color
* Size
* Alignment (beginning, centered, end)

## Graphics

Each method uses x, y to specify the placement on the coordinate
system, and w, h are used to designate the dimensions where
applicable.

* Ellipse -- centered at (x,y), sized at (w,h)
* Rect
* Polygon
* Line
* Arc -- centered at the specified location, sized at (w, h), stroked
from angle1, to angle2
* Curve -- quadratic Bezier curve

Note that Square and Circle may be constructed from the more general
Rect and Ellipse (using equal width and height).
Also, if needed, a Polyline method may be constructed using Lines.
In the case of Ellipse an Rectangle, the (x, y) coordinates may
specify either the center of the object, or its upper left.

Line, Arc, Curve specify a stroke color and stroke width. Ellipse,
Rect and Polygon have a filled color, and are optionally stroked.

## Image

Image may be placed at any (x,y) location, using a specified width,
and height. A scaling factor (0-100) and opacity (0-100) may also be
applied.

## Colors

Colors may be specified as:

* RGBA (red, green, blue, alpha)
* SVG named colors (for example "red", "green", "steelblue")

## Transformations

Text and graphics elements may be altered according to:

* Translation in either the x, y direction or some combination
* Scale (0-100)
* Rotation (in degrees).

## Data Types

Both the coordinate system (x, y) and dimensions (width, height,
sizes, scaling, opacity, stroke width) are expressed as floating point
numbers ranging from 0.0 to 100.0. Degrees of rotation and scale
factors are also floating point.
The red, green, blue and alpha components of colors are integers
ranging from 0-255.
Font names and optionally colors are expressed as strings.

## Methods

Text (x, y, s, font, color, size, alignment)
Image (name, x, y, w, h, scale)
Line (x1, y1, x2, y2, strokecolor, strokewidth)
Arc (x1, y1, angle1, angle2, strokecolor, strokewidth)
Curve (bx, by, cx, cy, ex, ey, strokecolor, strokewidth)
Ellipse (x, y, w, h, fillcolor, strokecolor, strokewidth)
Rect (x, y, w, h, fillcolor, strokecolor, strokewidth)
Polygon (x, y, fillcolor, strokecolor, strokewidth)

Square (x, y, w, fillcolor, strokecolor, strokewidth)
Circle (x, y, r, fillcolor, strokecolor, strokewidth)

Rotate(degrees)
Translate(x, y)
Scale(f)