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Merge pull request #25 from zenozeng/ctx.arcTo

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implementation of ctx.prototype.arcTo
This commit is contained in:
clintjd 2015-06-16 15:07:21 -07:00
commit 5d82d36034
1 changed files with 110 additions and 1 deletions
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111
canvas2svg.js
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@ -507,6 +507,7 @@
// Note that there is only one current default path, it is not part of the drawing state.
// See also: https://html.spec.whatwg.org/multipage/scripting.html#current-default-path
this.__currentDefaultPath = "";
this.__currentPosition = {};
path = this.__createElement("path", {}, true);
parent = this.__closestGroupOrSvg();
@ -544,6 +545,9 @@
if(this.__currentElement.nodeName !== "path") {
this.beginPath();
}
// creates a new subpath with the given point
this.__currentPosition = {x: x, y: y};
this.__addPathCommand(format("M {x} {y}", {x:x, y:y}));
};
@ -558,6 +562,7 @@
* Adds a line to command
*/
ctx.prototype.lineTo = function(x, y){
this.__currentPosition = {x: x, y: y};
if (this.__currentDefaultPath.indexOf('M') > -1) {
this.__addPathCommand(format("L {x} {y}", {x:x, y:y}));
} else {
@ -569,6 +574,7 @@
* Add a bezier command
*/
ctx.prototype.bezierCurveTo = function(cp1x, cp1y, cp2x, cp2y, x, y) {
this.__currentPosition = {x: x, y: y};
this.__addPathCommand(format("C {cp1x} {cp1y} {cp2x} {cp2y} {x} {y}",
{cp1x:cp1x, cp1y:cp1y, cp2x:cp2x, cp2y:cp2y, x:x, y:y}));
};
@ -577,9 +583,112 @@
* Adds a quadratic curve to command
*/
ctx.prototype.quadraticCurveTo = function(cpx, cpy, x, y){
this.__currentPosition = {x: x, y: y};
this.__addPathCommand(format("Q {cpx} {cpy} {x} {y}", {cpx:cpx, cpy:cpy, x:x, y:y}));
};
/**
* Return a new normalized vector of given vector
*/
var normalize = function(vector) {
var len = Math.sqrt(vector[0] * vector[0] + vector[1] * vector[1]);
return [vector[0] / len, vector[1] / len];
};
/**
* Adds the arcTo to the current path
*
* @see http://www.w3.org/TR/2015/WD-2dcontext-20150514/#dom-context-2d-arcto
*/
ctx.prototype.arcTo = function(x1, y1, x2, y2, radius) {
// Let the point (x0, y0) be the last point in the subpath.
var x0 = this.__currentPosition && this.__currentPosition.x;
var y0 = this.__currentPosition && this.__currentPosition.y;
// First ensure there is a subpath for (x1, y1).
if (typeof x0 == "undefined" || typeof y0 == "undefined") {
return;
}
// Negative values for radius must cause the implementation to throw an IndexSizeError exception.
if (radius < 0) {
throw new Error("IndexSizeError: The radius provided (" + radius + ") is negative.");
}
// If the point (x0, y0) is equal to the point (x1, y1),
// or if the point (x1, y1) is equal to the point (x2, y2),
// or if the radius radius is zero,
// then the method must add the point (x1, y1) to the subpath,
// and connect that point to the previous point (x0, y0) by a straight line.
if (((x0 === x1) && (y0 === y1))
|| ((x1 === x2) && (y1 === y2))
|| (radius === 0)) {
this.lineTo(x1, y1);
return;
}
// Otherwise, if the points (x0, y0), (x1, y1), and (x2, y2) all lie on a single straight line,
// then the method must add the point (x1, y1) to the subpath,
// and connect that point to the previous point (x0, y0) by a straight line.
var unit_vec_p1_p0 = normalize([x0 - x1, y0 - y1]);
var unit_vec_p1_p2 = normalize([x2 - x1, y2 - y1]);
if (unit_vec_p1_p0[0] * unit_vec_p1_p2[1] === unit_vec_p1_p0[1] * unit_vec_p1_p2[0]) {
this.lineTo(x1, y1);
return;
}
// Otherwise, let The Arc be the shortest arc given by circumference of the circle that has radius radius,
// and that has one point tangent to the half-infinite line that crosses the point (x0, y0) and ends at the point (x1, y1),
// and that has a different point tangent to the half-infinite line that ends at the point (x1, y1), and crosses the point (x2, y2).
// The points at which this circle touches these two lines are called the start and end tangent points respectively.
// note that both vectors are unit vectors, so the length is 1
var cos = (unit_vec_p1_p0[0] * unit_vec_p1_p2[0] + unit_vec_p1_p0[1] * unit_vec_p1_p2[1]);
var theta = Math.acos(Math.abs(cos));
// Calculate origin
var unit_vec_p1_origin = normalize([
unit_vec_p1_p0[0] + unit_vec_p1_p2[0],
unit_vec_p1_p0[1] + unit_vec_p1_p2[1]
]);
var len_p1_origin = radius / Math.sin(theta / 2);
var x = x1 + len_p1_origin * unit_vec_p1_origin[0];
var y = y1 + len_p1_origin * unit_vec_p1_origin[1];
// Calculate start angle and end angle
// rotate 90deg clockwise (note that y axis points to its down)
var unit_vec_origin_start_tangent = [
-unit_vec_p1_p0[1],
unit_vec_p1_p0[0]
];
// rotate 90deg counter clockwise (note that y axis points to its down)
var unit_vec_origin_end_tangent = [
unit_vec_p1_p2[1],
-unit_vec_p1_p2[0]
];
var getAngle = function(vector) {
// get angle (clockwise) between vector and (1, 0)
var x = vector[0];
var y = vector[1];
if (y >= 0) { // note that y axis points to its down
return Math.acos(x);
} else {
return -Math.acos(x);
}
};
var startAngle = getAngle(unit_vec_origin_start_tangent);
var endAngle = getAngle(unit_vec_origin_end_tangent);
// Connect the point (x0, y0) to the start tangent point by a straight line
this.lineTo(x + unit_vec_origin_start_tangent[0] * radius,
y + unit_vec_origin_start_tangent[1] * radius);
// Connect the start tangent point to the end tangent point by arc
// and adding the end tangent point to the subpath.
this.arc(x, y, radius, startAngle, endAngle);
};
/**
* Sets the stroke property on the current element
*/
@ -840,6 +949,7 @@
this.__addPathCommand(format("A {rx} {ry} {xAxisRotation} {largeArcFlag} {sweepFlag} {endX} {endY}",
{rx:radius, ry:radius, xAxisRotation:0, largeArcFlag:largeArcFlag, sweepFlag:sweepFlag, endX:endX, endY:endY}));
this.__currentPosition = {x: endX, y: endY};
};
/**
@ -983,7 +1093,6 @@
ctx.prototype.getImageData = function(){};
ctx.prototype.putImageData = function(){};
ctx.prototype.globalCompositeOperation = function(){};
ctx.prototype.arcTo = function(){};
ctx.prototype.setTransform = function(){};
//add options for alternative namespace