HTML5推出也有很长一段时间了，一直没有学习过，闲来无事学习开发个游戏吧。 用javascript+canvas编写一个 五彩连珠的游戏。
Canvas 画布
标签<canvas id="canvas" ></canvas>，很简单和普通的tag没区别。 关键在于js对他的操作。先看个示例代码：
<canvas id="canvas" height="100" width="100"></canvas><script>var canvas = document.getElementById("canvas");var ctx = canvas.getContext("2d");ctx.beginPath();ctx.moveTo(50,10);ctx.lineTo(50,90);ctx.moveTo(10,50);ctx.lineTo(90,50);ctx.strokeStyle="red";ctx.stroke();</script>
你能看到想到我画的是什么吗？ ctx是canvas的绘制的类型2D的，以后会支持3D，那木，目前基于canvas的绘制都是调用2d context的方法。所以要了解绘制各种图形，得先看看他的api。
interfaceCanvasRenderingContext2D{// back-reference to the canvasreadonly attribute HTMLCanvasElement canvas;// statevoid save(); // push state on state stackvoid restore(); // pop state stack and restore state// transformations (default transform is the identity matrix)void scale(in double x, in double y);void rotate(in double angle);void translate(in double x, in double y);void transform(in double a, in double b, in double c, in double d, in double e, in double f);void setTransform(in double a, in double b, in double c, in double d, in double e, in double f);// compositingattribute double globalAlpha; // (default 1.0)attribute DOMString globalCompositeOperation; // (default source-over)// colors and stylesattribute any strokeStyle; // (default black)attribute any fillStyle; // (default black)CanvasGradient createLinearGradient(in double x0, in double y0, in double x1, in double y1);CanvasGradient createRadialGradient(in double x0, in double y0, in double r0, in double x1, in double y1, in double r1);CanvasPattern createPattern(in HTMLImageElement image, in DOMString repetition);CanvasPattern createPattern(in HTMLCanvasElement image, in DOMString repetition);CanvasPattern createPattern(in HTMLVideoElement image, in DOMString repetition);// line caps/joinsattribute double lineWidth; // (default 1)attribute DOMString lineCap; // "butt", "round", "square" (default "butt")attribute DOMString lineJoin; // "round", "bevel", "miter" (default "miter")attribute double miterLimit; // (default 10)// shadowsattribute double shadowOffsetX; // (default 0)attribute double shadowOffsetY; // (default 0)attribute double shadowBlur; // (default 0)attribute DOMString shadowColor; // (default transparent black)// rectsvoid clearRect(in double x, in double y, in double w, in double h);void fillRect(in double x, in double y, in double w, in double h);void strokeRect(in double x, in double y, in double w, in double h);// path APIvoid beginPath();void closePath();void moveTo(in double x, in double y);void lineTo(in double x, in double y);void quadraticCurveTo(in double cpx, in double cpy, in double x, in double y);void bezierCurveTo(in double cp1x, in double cp1y, in double cp2x, in double cp2y, in double x, in double y);void arcTo(in double x1, in double y1, in double x2, in double y2, in double radius);void rect(in double x, in double y, in double w, in double h);void arc(in double x, in double y, in double radius, in double startAngle, in double endAngle, in optional boolean anticlockwise);void fill();void stroke();void clip();boolean isPointInPath(in double x, in double y);// Focus managementboolean drawFocusRing(in Element element, in optional boolean canDrawCustom);// Caret and selection managementlong caretBlinkRate();boolean setCaretSelectionRect(in Element element, in double x, in double y, in double w, in double h);// textattribute DOMString font; // (default 10px sans-serif)attribute DOMString textAlign; // "start", "end", "left", "right", "center" (default: "start")attribute DOMString textBaseline; // "top", "hanging", "middle", "alphabetic", "ideographic", "bottom" (default: "alphabetic")void fillText(in DOMString text, in double x, in double y, in optional double maxWidth);void strokeText(in DOMString text, in double x, in double y, in optional double maxWidth);TextMetrics measureText(in DOMString text);// drawing imagesvoid drawImage(in HTMLImageElement image, in double dx, in double dy, in optional double dw, in double dh);void drawImage(in HTMLImageElement image, in double sx, in double sy, in double sw, in double sh, in double dx, in double dy, in double dw, in double dh);void drawImage(in HTMLCanvasElement image, in double dx, in double dy, in optional double dw, in double dh);void drawImage(in HTMLCanvasElement image, in double sx, in double sy, in double sw, in double sh, in double dx, in double dy, in double dw, in double dh);void drawImage(in HTMLVideoElement image, in double dx, in double dy, in optional double dw, in double dh);void drawImage(in HTMLVideoElement image, in double sx, in double sy, in double sw, in double sh, in double dx, in double dy, in double dw, in double dh);// pixel manipulationImageData createImageData(in double sw, in double sh);ImageData createImageData(in ImageData imagedata);ImageData getImageData(in double sx, in double sy, in double sw, in double sh);void putImageData(in ImageData imagedata, in double dx, in double dy, in optional double dirtyX, in double dirtyY, in double dirtyWidth, in double dirtyHeight);};interfaceCanvasGradient{// opaque objectvoid addColorStop(in double offset, in DOMString color);};interfaceCanvasPattern{// opaque object};interfaceTextMetrics{readonly attribute double width;};interfaceImageData{readonly attribute unsigned long width;readonly attribute unsigned long height;readonly attribute CanvasPixelArray data;};interfaceCanvasPixelArray{readonly attribute unsigned long length;getter octet (in unsigned long index);setter void (in unsigned long index, in octet value);};
上面的内容是我粘贴的官方的，一目了然。
既然我们知道了lineTo和moveTo的功能，那么我们先把游戏的格子棋盘先画出来：
<canvas id="canvas" height="600" width="780" style="border:solid 1px #369;background:#333"></canvas><script>var canvas = document.getElementById("canvas");var ctx = canvas.getContext("2d");drawMap();function drawMap(){var start = 10;ctx.beginPath();var cell = 30;var max = cell * 9 + start;//ctx.strokeRect(10,10,max,max);ctx.moveTo(start,start);for(var i = 0;i <= 9 ;i++){var p = i * cell + start + 0.5;ctx.lineTo(p,max);ctx.moveTo(p+cell,start);}for(var i = 0;i <= 9 ;i++){var p = i * cell + start + 0.5;ctx.moveTo(start,p);ctx.lineTo(max,p);}ctx.strokeStyle="#567";ctx.stroke();}</script>
从运行效果可以看到我们的棋盘是从10像素的位置开始画的，画了个9*9格子的五彩连珠棋盘。
今天入门就到这里，下一节讲怎么画一个球。。。
