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Thread: Draw program

  1. #1
    Join Date
    Oct 2012
    Posts
    16

    Draw program

    Hi

    I working on a drawing app using HTML 5 and canvas. And I'll get a strange situation. The app enables the user to change settings as linewidth and fillStyle. The problem is that, as I draw a circle (function drawCircle) and then a line... Then the last circle drawn on the canvas gets a stroke around it. Which is kinda buggy. Does anyone have an idea? Thank you very much.

    Code:
    // Setup event handlers
    
    	cb_canvas = document.getElementById("cbook");
    
    	cb_lastPoints = Array();
    
    	if (cb_canvas.getContext) {
    		cb_ctx = cb_canvas.getContext('2d');
    		cb_ctx.lineWidth = 20;
    		cb_ctx.strokeStyle = "#0052f8";
    		cb_ctx.lineJoin="round";
    		cb_ctx.lineCap="round"
    		cb_ctx.beginPath();
    
    		cb_canvas.onmousedown = startDraw;
    		cb_canvas.onmouseup = stopDraw;
    		cb_canvas.ontouchstart = startDraw;
    		cb_canvas.ontouchstop = stopDraw;
    		cb_canvas.ontouchmove = drawMouse;
    	}
    	
    	
    function startDraw(e) {
    	if (e.touches) {
    		// Touch event
    		for (var i = 1; i <= e.touches.length; i++) {
    			cb_lastPoints[i] = getCoords(e.touches[i - 1]); // Get info for finger #1
    		}
    	}
    	else {
    		// Mouse event
    		cb_lastPoints[0] = getCoords(e);
    		cb_canvas.onmousemove = drawMouse;
    	}
    	
    	return false;
    }
    
    // Called whenever cursor position changes after drawing has started
    function stopDraw(e) {
    	e.preventDefault();
    	cb_canvas.onmousemove = null;
    	drawCircle(e);
    }
    
    //Draw circle
    function drawCircle(e) {
    canvas.click(function(e) {
    	var canvasOffset = canvas.offset();
    	var canvasX = Math.floor(e.pageX-canvasOffset.left);
    	var canvasY = Math.floor(e.pageY-canvasOffset.top);
    	cb_ctx.beginPath();
    	//cb_ctx.lineWidth = 0;
     	cb_ctx.arc(canvasX,canvasY,cb_ctx.lineWidth/2,0,Math.PI*2,true);
     	cb_ctx.fillStyle = cb_ctx.strokeStyle;
     	cb_ctx.fill();
    });
    }
    
    function drawMouse(e) {
    	if (e.touches) {
    		// Touch Enabled
    		for (var i = 1; i <= e.touches.length; i++) {
    			var p = getCoords(e.touches[i - 1]); // Get info for finger i
    			cb_lastPoints[i] = drawLine(cb_lastPoints[i].x, cb_lastPoints[i].y, p.x, p.y);
    		}
    	}
    	else {
    		// Not touch enabled
    		var p = getCoords(e);
    
    		cb_lastPoints[0] = drawLine(cb_lastPoints[0].x, cb_lastPoints[0].y, p.x, p.y);
    	}
    	cb_ctx.stroke();
    	cb_ctx.closePath();
    	cb_ctx.beginPath();
    	return false;
    }
    
    // Draw a line on the canvas from (s)tart to (e)nd
    function drawLine(sX, sY, eX, eY) {
    	cb_ctx.moveTo(sX, sY);
    	cb_ctx.lineTo(eX, eY);
    	return { x: eX, y: eY };
    }
    
    
    // Get the coordinates for a mouse or touch event
    function getCoords(e) {
    	if (e.offsetX) {
    		return { x: e.offsetX, y: e.offsetY };
    	}
    	else if (e.layerX) {
    		return { x: e.layerX, y: e.layerY };
    	}
    	else {
    		return { x: e.pageX - cb_canvas.offsetLeft, y: e.pageY - cb_canvas.offsetTop };
    	}
    }

  2. #2
    Join Date
    Aug 2008
    Location
    Sweden
    Posts
    227
    Try calling beginPath() before drawing something new.

  3. #3
    Join Date
    Oct 2012
    Posts
    16
    Great. Its working. Thanks a lot.

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