Programming Scripts Articles - Page 24 of 37

For antialiasing, you need to set resampling quality.ctx.imageSmoothingQuality = "low|medium|high"Use an off-screen canvas to reduce the image to half −var c = document.createElement('canvas'), ocx = c.getContext('2d'); c.width = img.width * 0.5; c.height = img.height * 0.5; ocxx.drawImage(img, 0, 0, c.width, c.height);// drawing images reducing to half again and repeating itocx.drawImage(c, 0, 0, c.width * 0.5, cc.height * 0.5);

You can try to run the following code to draw an oval in HTML5 canvas −Example                                  // canvas          var c = document.getElementById('newCanvas');          var context = c.getContext('2d');          var cX = 0;          var cY = 0;          var radius = 40;                    context.save();          context.translate(c.width / 2, c.height / 2);          context.scale(2, 1);          context.beginPath();          context.arc(cX, cY, radius, 0, 2 * Math.PI, false);          context.restore();          context.fillStyle = '#000000';          context.fill();          context.lineWidth = 2;          context.strokeStyle = 'yellow';          context.stroke();           Output

localStorage is used to persist information across multiple sessions. It has a maximum size of 5MB.ExampleYou can try to run the following code snippet to check the size allocated −var sum = 0; // loop for size for(var i in localStorage) {    var amount = (localStorage[i].length * 2) / 1024 / 1024;    sum += amount;    document.write( i + " = " + amount.toFixed(2) + " MB"); } document.write( "Total = " + sum.toFixed(2) + " MB");

Html2Canvas is a JavaScript library that can take screenshot of the whole web page or specific part. It doesn’t take the screenshot but creates the view based on the page information.ExampleBelow given is an example code. Here, html2canvas.js script is included at the . The html2canvas() method is called. Returns the base64 value, which eventually creates image source or an image file.                         Take screenshot                                                      function screenshot(){             html2canvas(document.body).then(function(canvas) {                document.body.appendChild(canvas);             });          }          

For double buffering on the canvas, create a 2nd canvas element and draw to it. After that draw the image to the first canvas using the drawImage() method,// canvas element var canvas1 = document.getElementById('canvas'); var context1 = canvas1.getContext('2d'); // buffer canvas var canvas2 = document.createElement('canvas'); canvas2.width = 250; canvas2.height =250; var context2 = canvas2.getContext('2d'); // create on the canvas context2.beginPath(); context2.moveTo(10,10); context2.lineTo(10,30); context2.stroke(); //render the buffered canvas context1.drawImage(canvas2, 0, 0);

In Html, we can edit the content by using contenteditable attribute, it specifies whether the elements content is editable or not by the user. The property of contentEditable is set or returns if the content of an element is editable. Syntax The usage/syntax of editable content in HTML is − The above contenteditable attribute has two values true/false. True indicates that the element is editable. False indicates that the element cannot be edited. Example Following is the example, to create editable content in an HTML − This ... Read More

In this article, we are going to learn how to iterate a JavaScript object’s properties using jQuery. The simplest way to iterate over an object with JavaScript is to use a for in loop. The for statement will iterate over the objects as an array, but the loop will send the key to the object instead of an index as a parameter. This loop is used to iterate over all non-Symbol iterative properties of an object. The hasOwnProperty() method can be used to check if the property belongs to the object itself. The value of each key of the ... Read More

To get the value of the usemap attribute of an image, use the useMap property. You can try to run the following code to display the usemap attribute value −Example                                                var x = document.getElementById("myid").useMap;          document.write("Usemap: "+x);          

To set the border bottom properties in one declaration in JavaScript, use the borderBottom property. It allows you to set the border-bottom-width, border-bottom-style, and border-bottom-color.ExampleYou can try to run the following code to learn how to set border bottom properties −Live Demo                    #box {             border: 2px dashed blue;             width: 120px;             height: 120px;          }                     Set border bottom color                Demo Text          Demo Text                      function display() {             document.getElementById("box").style.borderBottom = "thin dashed #000000";          }          

Use the Number() method in JavaScript to convert to Number. You can try to run the following code to learn how to convert ["demo"] to Number in JavaScript −ExampleLive Demo           Convert ["demo"] to Number                var myVal = ["demo"];          document.write("Number: " + Number(myVal));