CANVAS 贝塞尔曲线

来源：互联网发布：php微信服务号开发教程编辑：程序博客网时间：2024/04/28 08:34
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<!DOCTYPE html>
<html>
    <head>
        <title>rect
        </title>
        <style>
          body{
            background: #eeeeee;
          }
 
 
            #canvas{
                background: #000000;
 
            }
        </style>
    </head>
    <body>
 
        <canvas id="canvas" width="1000" height="800">
            Canvas not supported
        </canvas>
 
 
 
        <script src="chapetal2.js"></script>
    </body>
</html>

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var canvas = document.getElementById("canvas"),
    context = canvas.getContext("2d"),
    ARROW_MARGIN = 30,
    POINT_RADIUS = 7,
    points = [
        { x: canvas.width - ARROW_MARGIN,y: canvas.height - ARROW_MARGIN },
 
        { x: canvas.width - ARROW_MARGIN*2,y: canvas.height - ARROW_MARGIN},
 
        { x: POINT_RADIUS,y: canvas.height/2 },
 
        { x: ARROW_MARGIN,y: canvas.height/2 - ARROW_MARGIN},
 
        { x:canvas.width - ARROW_MARGIN,y:ARROW_MARGIN},
 
        { x: canvas.width - ARROW_MARGIN,y: ARROW_MARGIN*2}
    ];
 
//Functions.................................................................
 
function drawPointer(x, y, strokeStyle, fillStyle){
    context.beginPath();
    context.fillStyle = fillStyle;
    context.strokeStyle = strokeStyle;
    context.lineWidth = 0.5;
    context.arc(x, y, POINT_RADIUS, 0, Math.PI*2, false);
    context.fill();
    context.stroke();
}
 
function drawBezierPoints(){
    var i ,
        strokeStyle,
        fillStyle;
    for(i = 0 ; i < points.length; ++i){
        fillStyle = i % 2 === 0 ? 'white' : 'blue',
        strokeStyle = i % 2 === 0 ? 'blue' : 'white';
        drawPointer(points[i].x, points[i].y,
                  strokeStyle, fillStyle);
    }
}
 
function drawArrow(){
    context.strokeStyle = 'white';
    context.fillStyle = 'cornflowerblue';
 
    context.moveTo(canvas.width - ARROW_MARGIN,ARROW_MARGIN*2);
 
    context.lineTo(canvas.width - ARROW_MARGIN,
                    canvas.height - ARROW_MARGIN*2);
 
    context.quadraticCurveTo(points[0].x, points[0].y,
                             points[1].x, points[1].y);
 
    context.lineTo(ARROW_MARGIN, canvas.height/2 + ARROW_MARGIN);
 
    context.quadraticCurveTo(points[2].x, points[2].y,
                              points[3].x, points[3].y);
 
    context.lineTo(canvas.width - ARROW_MARGIN*2,ARROW_MARGIN);
 
    context.quadraticCurveTo(points[4].x, points[4].y,
                             points[5].x, points[5].y);
 
    context.fill();
    context.stroke();
}
 
//Initialization..........................................................
 
context.clearRect(0, 0, canvas.width,canvas.height);
drawArrow();
drawBezierPoints();


三次方贝赛尔曲线：（可以变换两个方向）
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var canvas = document.getElementById("canvas"),
    context = canvas.getContext("2d"),
    endPoints = [{x: 130, y : 70}, { x: 430, y : 270},],
    controlPoints = [{ x: 130, y : 250}, { x: 450, y: 70}, ];
 
//Functions..................................................................
 
function drawGrid(color, stepx, stepy){
 
}
 
function drawBezierCurve(){
    context.strokeStyle = 'blue';
 
    context.beginPath();
    context.moveTo(endPoints[0].x, endPoints[0].y);
    context.bezierCurveTo(controlPoints[0].x, controlPoints[0].y,
                         controlPoints[1].x,controlPoints[1].y,
                         endPoints[1].x,endPoints[1].y);
    context.stroke();
}
 
function drawEndPoints(){
    context.strokeStyle = 'blue';
    context.fillStyle = 'red';
 
    endPoints.forEach(function (point){
        context.beginPath();
        context.arc(point.x, point.y, 5, 0, Math.PI*2, false);
        context.stroke();
        context.fill();
    });
}
 
function drawControlPoints(){
    context.strokeStyle = 'yellow';
    context.fillStyle = 'blue';
 
    controlPoints.forEach(function (point){
        context.beginPath();
        context.arc(point.x, point.y, 5, 0, Math.PI*2, false);
        context.stroke();
        context.fill();
    });
}
 
drawGrid('lightgray', 10, 10);
 
drawControlPoints();
drawEndPoints();
drawBezierCurve();

可拖动：
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<!DOCTYPE html>
<html>
    <head>
        <title>rect
        </title>
        <style>
          body{
            background: #eeeeee;
          }
 
          .floatingControls {
            position: absolute;
            left: 150px;
            top:100px;
            width: 300px;
            padding: 20px;
            border: thin solid rgba(0,0,0,0.3);
            background: rgba(0,0,200, 0.1);
            color: blue;
            font: 14px Arial;
            -webkit-box-shadow: rgba(0,0,0,0.2) 6px 6px 8px;
            -moz-box-shadow: rgba(0,0,0,0.2) 6px 6px 8px;
            box-shadow: rgba(0,0,0,0.2) 6px 6px 8px;
            display: none;
          }
          .floatingControls p {
            margin-top : 0px;
            margin-bottom:20px;
          }
 
          #controls {
            position: absolute;
            left: 20px;
            top:25px;
          }
 
          #canvas {
            background: #ffffff;
            cursor: pointer;
            margin-left: 10px;
            margin-top: 10px;
            -webkit-box-shadow: 4px 4px 8px rgba(0,0,0,0.5);
            -moz-box-shadow: 4px 4px 8px rgba(0,0,0,0.5);
            -box-shadow: 4px 4px 8px rgba(0,0,0,0.5);
          }
        </style>
    </head>
    <body>
        <canvas id="canvas" width = '605' height='400'>
          Canvas not supported
        </canvas>
 
       <div id = "controls">
          Stroke color:<select id="strokeStyleSelect">
            <option value="red">red</option>
            <option value="green">green</option>
            <option value="blue">blue</option>
            <option value="orange">orange</option>
            <option value="cornflowerblue">cornflowerblue</option>
            <option value="goldenrod">goldenrod</option>
            <option value="navy" selected>navy</option>
            <option value="purple" >purple</option>
        </select>
      Guidewires:
      <input id="guidewireCheckbox" type="checkbox" checked />
      <input id="eraseAllButton" type="button" value="Erase All" />
       </div>
 
       <div id="instructions" class="floatingControls">
          <p>Drag the curve end- and control points to
            change the shape of the curve.</p>
 
          <p>When you are done dragging end- and control points,
              click outside of the points to finalize the curve.</p>
 
          <input id = "instructionsOkayButton" type="button"
                value = "Okay" autofocus/>
          <input id = "instructionsNoMoreButton" type="button"
                value = "Do not show these instructions again"/>
       </div>
 
        <script src="drawBezier.js"></script>
    </body>
</html>

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var canvas = document.getElementById("canvas"),
    context = canvas.getContext('2d'),
    eraseAllButton = document.getElementById('eraseAllButton'),
    strokeStyleSelect = document.getElementById("strokeStyleSelect"),
    guidewireCheckbox = document.getElementById('guidewireCheckbox'),
    instructions = document.getElementById("instructions"),
    instructionsOkayButton =
        document.getElementById("instructionsOkayButton"),
    instructionsNoMoreButton =
        document.getElementById("instructionsNoMoreButton"),
 
    showInstructions = true,
 
    AXIS_MARGIN = 40,
    HORIZONTAL_TICK_SPACING = 10,
    VERTICAL_TICK_SPACING = 10,
    TICK_SIZE = 10,
 
    AXIS_ORIGIN = { x: AXIS_MARGIN, y: canvas.height-AXIS_MARGIN },
    AXIS_TOP = AXIS_MARGIN,
 
    AXIS_RIGHT = canvas.width - AXIS_MARGIN,
    AXIS_WIDTH = AXIS_RIGHT - AXIS_ORIGIN.x,
    AXIS_HEIGHT = AXIS_ORIGIN.y - AXIS_TOP,
 
    NUM_VERTICAL_TICKS = AXIS_HEIGHT / VERTICAL_TICK_SPACING,
    NUM_HORIZONTAL_TICKS = AXIS_WIDTH / HORIZONTAL_TICK_SPACING,
 
    GRID_STROKE_STYLE = 'lightblue',
    GRID_SPACING = 10,
 
    CONTROL_POINT_RADIUS = 5,
    CONTROL_POINT_STROKE_STYLE = 'blue',
    CONTROL_POINT_FILL_STYLE = 'rgba(255,255,0,0.5)',
 
    END_POINT_STROKE_STYLE = 'navy',
    END_POINT_FILL_STYLE = 'rgba(255,255,0,0.5)',
 
    END_POINT_STROKE_STYLE = 'navy',
    END_POINT_FILL_STYLE = 'rgba(0,255,0,0.5)',
 
    GUIDEWIRE_STROKE_STYLE = 'rgba(0,0,230,0.4)',
 
    drawingImageData, // Image data stored on mouse down events
    mousedown = {},     //Cursor location for last mouse down events
    rubberbandRect = {}, //Constantly update for mouse move events
 
    dragging = false,   //If true, user is dragging the Cursor
    draggingPoint = false, //End- or control point user is dragging
    endPoints = [ {} , {}], //Endpoint locations (x,y)
    controlPoints = [ {} , {} ], //Controle point locations (x ,y)
    editing = false,            // If true, user is editing the curve
 
    guidewires = guidewireCheckbox.checked;
 
//Functions ...........................................................
 
function drawGrid(color, stepx, stepy) {
    context.strokeStyle = color;
    context.lineWidth = 0.5;
 
    for (var i = stepx + 0.5; i < context.canvas.width; i += stepx) {
        context.beginPath();
        context.moveTo(i, 0);
        context.lineTo(i, context.canvas.height);
        context.stroke();
    }
 
    for(var i = stepy + 0.5; i < context.canvas.height; i += stepy) {
        context.beginPath();
        context.moveTo(0, i );
        context.lineTo(context.canvas.width, i);
        context.stroke();
    }
}
 
function windowToCanvas(x, y){
    var bbox = canvas.getBoundingClientRect();
 
    return { x: x - bbox.left * (canvas.width / bbox.width),
             y: y - bbox.top * (canvas.height /  bbox.height)
            };
}
 
//Save and restore drawing surface.....................................
 
function saveDrawingSurface() {
    drawingImageData = context.getImageData(0, 0,
                                        canvas.width,canvas.height);
}
 
function restoreDrawingSurface(){
    context.putImageData(drawingImageData, 0, 0);
}
 
//Rubber bands..........................................................
 
function updateRubberbandRectangle(loc) {
    rubberbandRect.width = Math.abs(loc.x - mousedown.x);
    rubberbandRect.height = Math.abs(loc.y - mousedown.y);
 
    if(loc.x > mousedown.x) rubberbandRect.left = mousedown.x;
    else                    rubberbandRect.left = loc.x;
 
    if (loc.y > mousedown.y) rubberbandRect.top = mousedown.y;
    else                     rubberbandRect.top = loc.y;
}
 
function drawBezierCurve() {
    context.beginPath();
    context.moveTo(endPoints[0].x, endPoints[0].y);
    context.bezierCurveTo(controlPoints[0].x, controlPoints[0].y,
                          controlPoints[1].x, controlPoints[1].y,
                          endPoints[1].x, endPoints[1].y);
    context.stroke();
}
 
function updateEndAndControlPoints() {
    endPoints[0].x = rubberbandRect.left;
    endPoints[0].y = rubberbandRect.top;
 
    endPoints[1].x = rubberbandRect.left + rubberbandRect.width;
    endPoints[1].y = rubberbandRect.top + rubberbandRect.height;
 
    controlPoints[0].x = rubberbandRect.left;
    controlPoints[0].y = rubberbandRect.top + rubberbandRect.height;
 
    controlPoints[1].x = rubberbandRect.left = rubberbandRect.width;
    controlPoints[1].y = rubberbandRect.top;
}
 
function drawRubberbandShape(loc) {
    updateEndAndControlPoints();
    drawBezierCurve();
}
 
function updateRubberband(loc) {
    updateRubberbandRectangle(loc);
    drawRubberbandShape(loc);
}
 
//Guidewires...................................................
 
function drawHorizontalGuidewire (y) {
    context.beginPath();
    context.moveTo(0, y + 0.5);
    context.lineTo(context.canvas.width, y + 0.5);
    context.stroke();
}
 
function drawVerticalGuidewire (x) {
    context.beginPath();
    context.moveTo(x + 0.5, 0);
    context.lineTo(x + 0.5, context.canvas.height);
    context.stroke();
}
 
function drawGuidewires(x, y) {
    context.save();
    context.strokeStyle = GUIDEWIRE_STROKE_STYLE;
    context.lineWidth = 0.5;
    drawVerticalGuidewire(x);
    drawHorizontalGuidewire(y);
    context.restore();
}
 
//Endpoints and control points......................................
 
function drawControlPoint(index) {
    context.beginPath();
    context.arc(controlPoints[index].x, controlPoints[index].y,
                CONTROL_POINT_RADIUS, 0, Math.PI*2, false);
    context.stroke();
    context.fill();
}
 
function drawControlPoints() {
    context.save();
    context.strokeStyle = CONTROL_POINT_STROKE_STYLE;
    context.fillStyle = CONTROL_POINT_FILL_STYLE;
    drawControlPoint(0);
    drawControlPoint(1);
    context.stroke();
    context.fill();
    context.restore();
}
 
function drawEndPoint(index) {
    context.beginPath();
    context.arc(endPoints[index].x, endPoints[index].y,
                CONTROL_POINT_RADIUS, 0 , Math.PI*2, false);
    context.stroke();
    context.fill();
}
 
function drawEndPoints() {
    context.save();
    context.strokeStyle = END_POINT_STROKE_STYLE;
    context.fillStyle = END_POINT_FILL_STYLE;
 
    drawEndPoint(0);
    drawEndPoint(1);
 
    context.stroke();
    context.fill();
    context.restore();
}
 
function drawControlAndEndPoints() {
    drawControlPoints();
    drawEndPoints();
}
 
function cursorInEndPoint(loc) {
    var pt;
 
    endPoints.forEach(function (point) {
        context.beginPath();
        context.arc(point.x, point.y,
                    CONTROL_POINT_RADIUS, 0, Math.PI*2, false);
        if(context.isPointInPath(loc.x, loc.y)) {
            pt = point;
        }
    });
    return pt;
}
 
function cursorInControlPoint(ioc) {
    var pt;
 
    controlPoints.forEach (function (point) {
        context.beginPath();
        context.arc(point.x, point.y,
                    CONTROL_POINT_RADIUS, 0 , Math.PI*2, false);
        if (context.isPointInPath(loc.x, loc.y)) {
            pt = point;
        }
    });
    return pt;
}
 
function updateDraggingPoint(loc) {
    draggingPoint.x = loc.x;
    draggingPoint.y = loc.y;
}
 
//Canvas event handlers.............................................
 
canvas.onmousedown = function (e) {
    var loc = windowToCanvas(e.clientX, e.clientY);
 
    e.preventDefault(); //Prevent cursor change
 
    if(!editing) {
        saveDrawingSurface();
        mousedown.x = loc.x;
        mousedown.y = loc.y;
        updateRubberbandRectangle(loc);
        dragging = true;
    }
    else {
        draggingPoint = cursorInControlPoint(loc);
 
        if(!draggingPoint) {
            draggingPoint = cursorInEndPoint(loc);
        }
    }
};
 
canvas.onmousemove = function (e) {
    var loc = windowToCanvas(e.clientX, e.clientY);
 
    if (dragging || draggingPoint) {
        e.preventDefault();
        restoreDrawingSurface();
 
        if(guidewires) {
            drawGuidewires(loc.x, loc.y);
        }
    }
 
    if(dragging) {
        updateRubberband(loc);
        drawControlAndEndPoints();
    }
    else if (draggingPoint) {
        updateDraggingPoint(loc);
        drawControlAndEndPoints();
        drawBezierCurve();
    }
};
 
canvas.onmouseup = function (e) {
    loc = windowToCanvas(e.clientX, e.clientY);
 
    restoreDrawingSurface();
 
    if(!editing) {
        updateRubberband(loc);
        drawControlAndEndPoints();
        dragging = false;
        editing = true;
        if(showInstructions) {
            instructions.style.display = 'inline';
        }
    }
    else {
        if (draggingPoint) drawControlAndEndPoints();
        else                editing = false;
 
        drawBezierCurve();
        draggingPoint = undefined;
    }
};
 
//Control event handlers........................................
 
eraseAllButton.onclick = function (e) {
    context.clearRect(0, 0, canvas.width, canvas.height);
    drawGrid(GRID_STROKE_STYLE, GRID_SPACING, GRID_SPACING);
 
    saveDrawingSurface();
 
    editing = false;
    dragging = false;
    draggingPoint = undefined;
};
 
strokeStyleSelect.onchange = function (e) {
    context.strokeStyle = strokeStyleSelect.value;
};
 
//Instructions event handlers....................................
 
instructionsOkayButton.onclick = function (e) {
    instructions.style.display = 'none';
};
 
instructionsNoMoreButton.onclick = function (e) {
    instructions.style.display = 'none';
    showInstructions = false;
};
 
//Initialization.....................................................
 
context.strokeStyle = strokeStyleSelect.value;
drawGrid(GRID_STROKE_STYLE, GRID_SPACING,GRID_SPACING);



​


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