Created
June 10, 2012 04:12
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Draw and rotate a rect in JavaScript Canvas.
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| <html> | |
| <head> | |
| <script type="text/javascript"> | |
| var app = { | |
| rect: { | |
| x: 100, | |
| y: 100, | |
| w: 100, | |
| h: 100, | |
| a: 0 | |
| }, | |
| draw: function() { | |
| var cv = document.getElementById("canvas"); | |
| var cx = cv.getContext("2d"); | |
| cx.save(); | |
| cx.clearRect(0, 0, cv.width, cv.height); | |
| var c = this.getRectCenter(); | |
| cx.translate(c.x, c.y); | |
| cx.rotate(Math.PI / (180.0 / this.rect.a)); | |
| var r = this.getRotatedRect(); | |
| cx.strokeRect(r.x, r.y, r.w, r.h); | |
| cx.restore(); | |
| }, | |
| getRectCenter: function() { | |
| return { | |
| x: this.rect.x + this.rect.w / 2, | |
| y: this.rect.y + this.rect.h / 2 | |
| }; | |
| }, | |
| getRotatedRect: function() { | |
| return { | |
| x: this.rect.w / -2, | |
| y: this.rect.h / -2, | |
| w: this.rect.w, | |
| h: this.rect.h | |
| }; | |
| }, | |
| moveH: function(n) { | |
| this.rect.x += n; | |
| this.draw(); | |
| }, | |
| moveV: function(n) { | |
| this.rect.y += n; | |
| this.draw(); | |
| }, | |
| rotate: function(n) { | |
| this.rect.a += n; | |
| this.draw(); | |
| }, | |
| onLeft: function() { | |
| this.moveH(-5); | |
| }, | |
| onRight: function() { | |
| this.moveH(5); | |
| }, | |
| onUp: function() { | |
| this.moveV(-5); | |
| }, | |
| onDown: function() { | |
| this.moveV(5); | |
| }, | |
| onCounterClockwise: function() { | |
| this.rotate(-5); | |
| }, | |
| onClockwise: function() { | |
| this.rotate(5); | |
| } | |
| }; | |
| </script> | |
| </head> | |
| <body onload="app.draw();"> | |
| <p> | |
| <input type="button" value="<" onclick="app.onLeft();"> | |
| <input type="button" value=">" onclick="app.onRight();"> | |
| <input type="button" value="Up" onclick="app.onUp();"> | |
| <input type="button" value="Dn" onclick="app.onDown();"> | |
| <input type="button" value="<<" onclick="app.onCounterClockwise();"> | |
| <input type="button" value=">>" onclick="app.onClockwise();"> | |
| </p> | |
| <p> | |
| <canvas id="canvas" width=640 height=480> | |
| Canvas | |
| </canvas> | |
| </p> | |
| <pre> | |
| <script type="text/javascript"> | |
| </script> | |
| </pre> | |
| </body> | |
| </html> | |
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