HTML5 Canvas图片操作简单实例1

1.加载显示图片

    <canvas id="canvasOne" class="myCanvas" width="500" height="500"></canvas>
    <script>
        var canvas = document.getElementById('canvasOne');
        var ctx = canvas.getContext('2d');
        //加载图片
        var img = new Image();
        img.onload = function () {
            ctx.clearRect(0, 0, canvas.width, canvas.height);
            ctx.drawImage(img, 0, 0, img.width, img.height);
        }
        img.src = '../images/1.jpg';
    </script>

2.获取Canvas数据，显示到img标签

    <canvas id="canvasOne" class="myCanvas" width="500" height="500"></canvas>
    <img id="imgOne" />
    <script>
        var canvas = document.getElementById('canvasOne');
        var ctx = canvas.getContext('2d');
        //加载图片，显示当前图片到其他地方
        var img = new Image();
        img.onload = function () {
            ctx.clearRect(0, 0, canvas.width, canvas.height);
            ctx.drawImage(img, 0, 0, img.width, img.height);
            //显示图片的部分内容到img图片标签
            var imgOne = document.getElementById('imgOne');
            imgOne.width = 1000;
            imgOne.height = 600;
            //图片内容显示当前画布显示的部分
            imgOne.src = canvas.toDataURL('image/png');
        }
        img.src = '../images/1.jpg';
    </script>

3.获取Canvas数据，显示到其他canvas中

    <canvas id="target" width="200" height="100"></canvas>
    <canvas id="canvasOne" class="myCanvas" width="500" height="500"></canvas>
    <script>
        var canvas = document.getElementById('canvasOne');
        var ctx = canvas.getContext('2d');
        var target = document.getElementById('target');
        //加载图片
        var img = new Image();
        img.onload = function () {
            ctx.clearRect(0, 0, canvas.width, canvas.height);
            //图片缩小,显示
            ctx.scale(0.5, 0.5);
            ctx.drawImage(img, 0, 0, img.width, img.height);

            //获取缩小后的像素，显示到其他canvas
            var imgData = ctx.getImageData(0, 0, 200, 100);
            var ctxTwo = target.getContext('2d');
            ctxTwo.putImageData(imgData, 0, 0);
        }
        img.src = '../images/1.jpg';
    </script>

4.Canvas中图片的平铺操作

    <canvas id="canvasOne" class="myCanvas" width="500" height="500"></canvas>
    <script>
        /***图片的背景显示***/
        var canvas = document.getElementById('canvasOne');
        var ctx = canvas.getContext('2d');
        //加载图片
        var img = new Image();
        img.onload = function () {
            ctx.beginPath();
            ctx.rect(0, 0, canvas.width, canvas.height);
            ctx.scale(0.1, 0.1);
            //平铺
            //ctx.fillStyle = ctx.createPattern(img, 'repeat');

            //水平方向 平铺
            //ctx.fillStyle = ctx.createPattern(img,'repeat-x');

            //垂直方向 平铺
            //ctx.fillStyle = ctx.createPattern(img, 'repeat-y');

            //禁用平铺
            ctx.fillStyle = ctx.createPattern(img, 'no-repeat');

            ctx.fill();
        }
        img.src = '../images/1.jpg';
    </script>

更多像素处理：

http://www.cnblogs.com/tianma3798/p/4264857.html

HTML5 Canvas显示本地图片实例1、Canvas预览图片实例1