HTML Canvas Application Drawing Board

Description

HTML Canvas Application Drawing Board

View in separate window 

<!DOCTYPE HTML>
<html>
    <head>
        <style>
            canvas {/*from  w w  w  .j ava  2  s  .c o  m*/
                border: 1px solid black;
                font-size: 13px;
                line-height: 1.5;
                color: #474747;
            }
            
            #toolbar {
                width: 590px;
                border: 1px solid black;
                border-bottom: 0px;
                padding: 5px;
                background-color: #f8f8f8;
            }
            
            input[type = 'text'] {
                width: 30px;
        margin: 0px 5px 0px 5px;
            }
            
            label {
                margin-left: 40px;
            }
            
            label:first-of-type {
                margin-left: 0px;
            }
            
            input[type = 'button'] {
                float: right;
            }
            
            #colorSquare {
                position: relative;
                display: inline-block;
                width: 20px;
                height: 20px;
                background-color: blue;
                top: 4px;
            }
        </style>
    <script>

            function addPoint(events, points){
                var context = events.getContext();
                var drawingPos = events.getMousePos();
                
                if (drawingPos !== null) {
                    points.push(drawingPos);
                }
            }
            
            function drawPath(canvas, points, canvasImg){
                var context = canvas.getContext("2d");
                
                // clear canvas
                context.clearRect(0, 0, canvas.width, canvas.height);
                
                // redraw canvas before path
                context.drawImage(canvasImg, 0, 0, canvas.width, canvas.height);
                
                // draw patch
                context.beginPath();
                context.lineTo(points[0].x, points[0].y);
                for (var n = 1; n < points.length; n++) {
                    var point = points[n];
                    context.lineTo(point.x, point.y);
                }
                context.stroke();
            }
            
            function updateColorSquare(){
                var red = document.getElementById("red").value;
                var green = document.getElementById("green").value;
                var blue = document.getElementById("blue").value;
                
                var colorSquare = document.getElementById("colorSquare");
                colorSquare.style.backgroundColor = "rgb(" + red + "," + green + "," + blue + ")";
            }
            
            function getCanvasImg(canvas){
                var img = new Image();
                img.src = canvas.toDataURL();
                return img;
            }
            
            window.onload = function(){
                var events = new Events("myCanvas");
                var canvas = events.getCanvas();
                var context = events.getContext();
                var isMouseDown = false;
                var canvasImg = getCanvasImg(canvas);
                var points = [];
                
                // initialize drawing params
                var red = document.getElementById("red").value;
                var green = document.getElementById("green").value;
                var blue = document.getElementById("blue").value;
                var size = document.getElementById("size").value;
                
                // attach listeners
                document.getElementById("red").addEventListener("keyup", function(evt){
                    updateColorSquare();
                }, false);
                
                document.getElementById("green").addEventListener("keyup", function(evt){
                    updateColorSquare();
                }, false);
                
                document.getElementById("blue").addEventListener("keyup", function(evt){
                    updateColorSquare();
                }, false);
                
                document.getElementById("clearButton").addEventListener("click", function(evt){
                    events.clear();
                    points = [];
                    canvasImg = getCanvasImg(canvas);
                }, false);
                
                document.getElementById("saveButton").addEventListener("click", function(evt){
                    // open new window with saved image so user
                    // can right click and save to their computer
                    window.open(canvas.toDataURL());
                }, false);
                
                canvas.addEventListener("mousedown", function(){
                    var drawingPos = events.getMousePos();
                    
                    // update drawing params
                    red = document.getElementById("red").value;
                    green = document.getElementById("green").value;
                    blue = document.getElementById("blue").value;
                    size = document.getElementById("size").value;
                    
                    // start drawing path
                    context.strokeStyle = "rgb(" + red + "," + green + "," + blue + ")";
                    context.lineWidth = size;
                    context.lineJoin = "round";
                    context.lineCap = "round";
                    addPoint(events, points);
                    isMouseDown = true;
                }, false);
                
                canvas.addEventListener("mouseup", function(){
                    isMouseDown = false;
                    if (points.length > 0) {
                        drawPath(this, points, canvasImg);
                        // reset points
                        points = [];
                    }
                    canvasImg = getCanvasImg(this);
                }, false);
                
                canvas.addEventListener("mouseout", function(){
                    if (document.createEvent) {
                        var evt = document.createEvent('MouseEvents');
                        evt.initEvent("mouseup", true, false);
                        this.dispatchEvent(evt);
                    }
                    else {
                        this.fireEvent("onmouseup");
                    }
                }, false);
                
                events.setDrawStage(function(){
                    if (isMouseDown) {
                        addPoint(this, points);
                        drawPath(canvas, points, canvasImg);
                    }
                });
            };
class Events {
    constructor(canvasId) {
        this.canvas = document.getElementById(canvasId);
        this.context = this.canvas.getContext("2d");
        this.drawStage = undefined;
        this.listening = false;
        
        // desktop flags
        this.mousePos = null;
        this.mouseDown = false;
        this.mouseUp = false;
        this.mouseOver = false;
        this.mouseMove = false;
        
        // mobile flags
        this.touchPos = null;
        this.touchStart = false;
        this.touchMove = false;
        this.touchEnd = false;
        
        // Region Events
        this.currentRegion = null;
        this.regionIndex = 0;
        this.lastRegionIndex = -1;
        this.mouseOverRegionIndex = -1;
    }

    getContext() {
        return this.context;
    }

    getCanvas() {
        return this.canvas;
    }

    clear() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }

    getCanvasPos() {
        let obj = this.getCanvas();
        let top = 0;
        let left = 0;
        while (obj.tagName != "BODY") {
            top += obj.offsetTop;
            left += obj.offsetLeft;
            obj = obj.offsetParent;
        }
        return {
            top: top,
            left: left
        };
    }

    setDrawStage(func) {
        this.drawStage = func;
        this.listen();
    }

    reset(evt) {
        if (!evt) {
            evt = window.event;
        }
        
        this.setMousePosition(evt);
        this.setTouchPosition(evt);
        this.regionIndex = 0;
        
        if (!this.animating && this.drawStage !== undefined) {
            this.drawStage();
        }
        
        // desktop flags
        this.mouseOver = false;
        this.mouseMove = false;
        this.mouseDown = false;
        this.mouseUp = false;
        
        // mobile touch flags
        this.touchStart = false;
        this.touchMove = false;
        this.touchEnd = false;
    }

    listen() {
        const that = this;
        
        if (this.drawStage !== undefined) {
            this.drawStage();
        }
        
        // desktop events
        this.canvas.addEventListener("mousedown", evt => {
            that.mouseDown = true;
            that.reset(evt);
        }, false);
        
        this.canvas.addEventListener("mousemove", evt => {
            that.reset(evt);
        }, false);
        
        this.canvas.addEventListener("mouseup", evt => {
            that.mouseUp = true;
            that.reset(evt);
        }, false);
        
        this.canvas.addEventListener("mouseover", evt => {
            that.reset(evt);
        }, false);
        
        this.canvas.addEventListener("mouseout", evt => {
            that.mousePos = null;
        }, false);
        
        // mobile events
        this.canvas.addEventListener("touchstart", evt => {
            evt.preventDefault();
            that.touchStart = true;
            that.reset(evt);
        }, false);
        
        this.canvas.addEventListener("touchmove", evt => {
            evt.preventDefault();
            that.reset(evt);
        }, false);
        
        this.canvas.addEventListener("touchend", evt => {
            evt.preventDefault();
            that.touchEnd = true;
            that.reset(evt);
        }, false);
    }

    getMousePos(evt) {
        return this.mousePos;
    }

    getTouchPos(evt) {
        return this.touchPos;
    }

    setMousePosition(evt) {
        const mouseX = evt.clientX - this.getCanvasPos().left + window.pageXOffset;
        const mouseY = evt.clientY - this.getCanvasPos().top + window.pageYOffset;
        this.mousePos = {
            x: mouseX,
            y: mouseY
        };
    }

    setTouchPosition(evt) {
        if (evt.touches !== undefined && evt.touches.length == 1) { // Only deal with one finger
            const touch = evt.touches[0]; // Get the information for finger #1
            const touchX = touch.pageX - this.getCanvasPos().left + window.pageXOffset;
            const touchY = touch.pageY - this.getCanvasPos().top + window.pageYOffset;
            
            this.touchPos = {
                x: touchX,
                y: touchY
            };
        }
    }

    beginRegion() {
        this.currentRegion = {};
        this.regionIndex++;
    }

    addRegionEventListener(type, func) {
        let event = (type.indexOf('touch') == -1) ? `on${type}` : type;
        this.currentRegion[event] = func;
    }

    closeRegion() {
        const pos = this.touchPos || this.mousePos;
        
        if (pos !== null && this.context.isPointInPath(pos.x, pos.y)) {
            if (this.lastRegionIndex != this.regionIndex) {
                this.lastRegionIndex = this.regionIndex;
            }
            
            // handle onmousedown
            if (this.mouseDown && this.currentRegion.onmousedown !== undefined) {
                this.currentRegion.onmousedown();
                this.mouseDown = false;
            }
            
            // handle onmouseup
            else if (this.mouseUp && this.currentRegion.onmouseup !== undefined) {
                this.currentRegion.onmouseup();
                this.mouseUp = false;
            }
            
            // handle onmouseover
            else if (!this.mouseOver && this.regionIndex != this.mouseOverRegionIndex && this.currentRegion.onmouseover !== undefined) {
                this.currentRegion.onmouseover();
                this.mouseOver = true;
                this.mouseOverRegionIndex = this.regionIndex;
            }
            
            // handle onmousemove
            else if (!this.mouseMove && this.currentRegion.onmousemove !== undefined) {
                this.currentRegion.onmousemove();
                this.mouseMove = true;
            }
            
            // handle touchstart
            if (this.touchStart && this.currentRegion.touchstart !== undefined) {
                this.currentRegion.touchstart();
                this.touchStart = false;
            }
            
            // handle touchend
            if (this.touchEnd && this.currentRegion.touchend !== undefined) {
                this.currentRegion.touchend();
                this.touchEnd = false;
            }
            
            // handle touchmove
            if (!this.touchMove && this.currentRegion.touchmove !== undefined) {
                this.currentRegion.touchmove();
                this.touchMove = true;
            }
            
        }
        else if (this.regionIndex == this.lastRegionIndex) {
            this.lastRegionIndex = -1;
            this.mouseOverRegionIndex = -1;
            
            // handle mouseout condition
            if (this.currentRegion.onmouseout !== undefined) {
                this.currentRegion.onmouseout();
            }
        }
    }
}

        </script>
    </head>
    <body>
        <div id="toolbar">
            <label>
                Color
            </label>
            R: <input type="text" id="red" maxlength="3" class="short" value="0">G: <input type="text" id="green" maxlength="3" class="short" value="0">B: <input type="text" id="blue" maxlength="3" class="short" value="255">
            <div id="colorSquare">
            </div>
            <label>
                Size:
            </label>
            <input type="text" id="size" maxlength="3" class="short" value="20">px<input type="button" id="clearButton" value="Clear"><input type="button" id="saveButton" value="Save">
        </div>
        <canvas id="myCanvas" width="600" height="250">
        </canvas>
    </body>
</html>



PreviousNext

Related