javascript - 如何将渲染矩形的canvas代码转换为svg

Question

我有用于拖动和调整矩形大小的 Canvas 代码。但我无法将此 Canvas 代码转换为 svg。如何将 Canvas 代码转换为 svg。

那个 stackoverflow 链接对我来说没有用。

提前致谢。

var canvas = document.getElementById('canvas'),
    ctx = canvas.getContext('2d'),
    rect = {
        x: 150,
        y: 100,
        w: 123,
        h: 58
    },
    handlesSize = 8,
    currentHandle = false,
    drag = false;

function init() {
    canvas.addEventListener('mousedown', mouseDown, false);
    canvas.addEventListener('mouseup', mouseUp, false);
    canvas.addEventListener('mousemove', mouseMove, false);
}

function point(x, y) {
    return {
        x: x,
        y: y
    };
}

function dist(p1, p2) {
    return Math.sqrt((p2.x - p1.x) * (p2.x - p1.x) + (p2.y - p1.y) * (p2.y - p1.y));
}

function getHandle(mouse) {
    if (dist(mouse, point(rect.x, rect.y)) <= handlesSize) return 'topleft';
    if (dist(mouse, point(rect.x + rect.w, rect.y)) <= handlesSize) return 'topright';
    if (dist(mouse, point(rect.x, rect.y + rect.h)) <= handlesSize) return 'bottomleft';
    if (dist(mouse, point(rect.x + rect.w, rect.y + rect.h)) <= handlesSize) return 'bottomright';
    if (dist(mouse, point(rect.x + rect.w / 2, rect.y)) <= handlesSize) return 'top';
    if (dist(mouse, point(rect.x, rect.y + rect.h / 2)) <= handlesSize) return 'left';
    if (dist(mouse, point(rect.x + rect.w / 2, rect.y + rect.h)) <= handlesSize) return 'bottom';
    if (dist(mouse, point(rect.x + rect.w, rect.y + rect.h / 2)) <= handlesSize) return 'right';
    return false;
}

function mouseDown(e) {
    if (currentHandle) drag = true;
    draw();
}

function mouseUp() {
    drag = false;
    currentHandle = false;
    draw();
}

function mouseMove(e) {
    var previousHandle = currentHandle;
    if (!drag) currentHandle = getHandle(point(e.pageX - this.offsetLeft, e.pageY - this.offsetTop));
    if (currentHandle && drag) {
        var mousePos = point(e.pageX - this.offsetLeft, e.pageY - this.offsetTop);
        switch (currentHandle) {
            case 'topleft':
                rect.w += rect.x - mousePos.x;
                rect.h += rect.y - mousePos.y;
                rect.x = mousePos.x;
                rect.y = mousePos.y;
                break;
            case 'topright':
                rect.w = mousePos.x - rect.x;
                rect.h += rect.y - mousePos.y;
                rect.y = mousePos.y;
                break;
            case 'bottomleft':
                rect.w += rect.x - mousePos.x;
                rect.x = mousePos.x;
                rect.h = mousePos.y - rect.y;
                break;
            case 'bottomright':
                rect.w = mousePos.x - rect.x;
                rect.h = mousePos.y - rect.y;
                break;

            case 'top':
                rect.h += rect.y - mousePos.y;
                rect.y = mousePos.y;
                break;

            case 'left':
                rect.w += rect.x - mousePos.x;
                rect.x = mousePos.x;
                break;

            case 'bottom':
                rect.h = mousePos.y - rect.y;
                break;

            case 'right':
                rect.w = mousePos.x - rect.x;
                break;
        }
    }
    if (drag || currentHandle != previousHandle) draw();
}

function draw() {
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    ctx.fillStyle = 'black';
    ctx.fillRect(rect.x, rect.y, rect.w, rect.h);
    if (currentHandle) {
        var posHandle = point(0, 0);
        switch (currentHandle) {
            case 'topleft':
                posHandle.x = rect.x;
                posHandle.y = rect.y;
                break;
            case 'topright':
                posHandle.x = rect.x + rect.w;
                posHandle.y = rect.y;
                break;
            case 'bottomleft':
                posHandle.x = rect.x;
                posHandle.y = rect.y + rect.h;
                break;
            case 'bottomright':
                posHandle.x = rect.x + rect.w;
                posHandle.y = rect.y + rect.h;
                break;
            case 'top':
                posHandle.x = rect.x + rect.w / 2;
                posHandle.y = rect.y;
                break;
            case 'left':
                posHandle.x = rect.x;
                posHandle.y = rect.y + rect.h / 2;
                break;
            case 'bottom':
                posHandle.x = rect.x + rect.w / 2;
                posHandle.y = rect.y + rect.h;
                break;
            case 'right':
                posHandle.x = rect.x + rect.w;
                posHandle.y = rect.y + rect.h / 2;
                break;
        }
        ctx.globalCompositeOperation = 'xor';
        ctx.beginPath();
        ctx.arc(posHandle.x, posHandle.y, handlesSize, 0, 2 * Math.PI);
        ctx.fill();
        ctx.globalCompositeOperation = 'source-over';
    }
}

init();
draw();

这里是用于在 Canvas 中渲染矩形的 fiddle 链接:

http://jsfiddle.net/BaliBalo/9HXMG/

Answer 1

将其转换为 SVG 非常简单。

唯一的小问题是我们必须添加一些处理来满足矩形宽度或高度为负数的情况。 Canvas2D 不介意这一点，但 SVG 介意。

此外，在绘制拖动 handle 时，没有一种简单的方法来模拟 XOR 操作。所以我只是把它们变成纯蓝色。

var canvas = document.getElementById('canvas'),
    rect = {
        x: 150,
        y: 100,
        w: 123,
        h: 58
    },
    handlesSize = 8,
    currentHandle = false,
    drag = false
    svgns = 'http://www.w3.org/2000/svg';

function init() {
    canvas.addEventListener('mousedown', mouseDown, false);
    canvas.addEventListener('mouseup', mouseUp, false);
    canvas.addEventListener('mousemove', mouseMove, false);
}

function point(x, y) {
    return {
        x: x,
        y: y
    };
}

function dist(p1, p2) {
    return Math.sqrt((p2.x - p1.x) * (p2.x - p1.x) + (p2.y - p1.y) * (p2.y - p1.y));
}

function getHandle(mouse) {
    if (dist(mouse, point(rect.x, rect.y)) <= handlesSize) return 'topleft';
    if (dist(mouse, point(rect.x + rect.w, rect.y)) <= handlesSize) return 'topright';
    if (dist(mouse, point(rect.x, rect.y + rect.h)) <= handlesSize) return 'bottomleft';
    if (dist(mouse, point(rect.x + rect.w, rect.y + rect.h)) <= handlesSize) return 'bottomright';
    if (dist(mouse, point(rect.x + rect.w / 2, rect.y)) <= handlesSize) return 'top';
    if (dist(mouse, point(rect.x, rect.y + rect.h / 2)) <= handlesSize) return 'left';
    if (dist(mouse, point(rect.x + rect.w / 2, rect.y + rect.h)) <= handlesSize) return 'bottom';
    if (dist(mouse, point(rect.x + rect.w, rect.y + rect.h / 2)) <= handlesSize) return 'right';
    return false;
}

function mouseDown(e) {
    if (currentHandle) drag = true;
    draw();
}

function mouseUp() {
    drag = false;
    currentHandle = false;
    draw();
}

function mouseMove(e) {
    var previousHandle = currentHandle;
    var svgPos = this.getBoundingClientRect();
    if (!drag) currentHandle = getHandle(point(e.pageX - svgPos.left, e.pageY - svgPos.top));
    if (currentHandle && drag) {
        var mousePos = point(e.pageX - svgPos.left, e.pageY - svgPos.top);
        switch (currentHandle) {
            case 'topleft':
                rect.w += rect.x - mousePos.x;
                rect.h += rect.y - mousePos.y;
                rect.x = mousePos.x;
                rect.y = mousePos.y;
                break;
            case 'topright':
                rect.w = mousePos.x - rect.x;
                rect.h += rect.y - mousePos.y;
                rect.y = mousePos.y;
                break;
            case 'bottomleft':
                rect.w += rect.x - mousePos.x;
                rect.x = mousePos.x;
                rect.h = mousePos.y - rect.y;
                break;
            case 'bottomright':
                rect.w = mousePos.x - rect.x;
                rect.h = mousePos.y - rect.y;
                break;

            case 'top':
                rect.h += rect.y - mousePos.y;
                rect.y = mousePos.y;
                break;

            case 'left':
                rect.w += rect.x - mousePos.x;
                rect.x = mousePos.x;
                break;

            case 'bottom':
                rect.h = mousePos.y - rect.y;
                break;

            case 'right':
                rect.w = mousePos.x - rect.x;
                break;
        }
    }
    if (drag || currentHandle != previousHandle) draw();
}

function draw() {
    //ctx.clearRect(0, 0, canvas.width, canvas.height);
    while (canvas.firstChild) {
        canvas.removeChild(canvas.firstChild);
    }
    //ctx.fillStyle = 'black';
    //ctx.fillRect(rect.x, rect.y, rect.w, rect.h);
    var svgrect = document.createElementNS(svgns, 'rect');
    svgrect.setAttribute('x', Math.min(rect.x, rect.x+rect.w));
    svgrect.setAttribute('y', Math.min(rect.y, rect.y+rect.h));
    svgrect.setAttribute('width', Math.abs(rect.w));
    svgrect.setAttribute('height', Math.abs(rect.h));
    canvas.appendChild(svgrect);

    if (currentHandle) {
        var posHandle = point(0, 0);
        switch (currentHandle) {
            case 'topleft':
                posHandle.x = rect.x;
                posHandle.y = rect.y;
                break;
            case 'topright':
                posHandle.x = rect.x + rect.w;
                posHandle.y = rect.y;
                break;
            case 'bottomleft':
                posHandle.x = rect.x;
                posHandle.y = rect.y + rect.h;
                break;
            case 'bottomright':
                posHandle.x = rect.x + rect.w;
                posHandle.y = rect.y + rect.h;
                break;
            case 'top':
                posHandle.x = rect.x + rect.w / 2;
                posHandle.y = rect.y;
                break;
            case 'left':
                posHandle.x = rect.x;
                posHandle.y = rect.y + rect.h / 2;
                break;
            case 'bottom':
                posHandle.x = rect.x + rect.w / 2;
                posHandle.y = rect.y + rect.h;
                break;
            case 'right':
                posHandle.x = rect.x + rect.w;
                posHandle.y = rect.y + rect.h / 2;
                break;
        }
        //ctx.globalCompositeOperation = 'xor';
        //ctx.beginPath();
        //ctx.arc(posHandle.x, posHandle.y, handlesSize, 0, 2 * Math.PI);
        //ctx.fill();
        //ctx.globalCompositeOperation = 'source-over';
        var circ = document.createElementNS(svgns, 'circle');
        circ.setAttribute('cx', posHandle.x);
        circ.setAttribute('cy', posHandle.y);
        circ.setAttribute('r', handlesSize);
        circ.setAttribute('fill', 'blue');
        canvas.appendChild(circ);
    }
}

init();
draw();

<svg id="canvas" width="500" height="500"></svg>