如何用canvas实现自定义头像功能--百分百源码网

如何用canvas实现自定义头像功能-

发布时间：08/01 来源：未知浏览：关键词：

这次给大家带来如何用canvas实现自定义头像功能，用canvas实现自定义头像功能的注意事项是什么，下面就是实战案例，一起来看一下。这次给大家带来如何用canvas实现自定义头像功能，用canvas实现自定义头像功能的注意事项是什么，下面就是实战案例，一起来看一下。

写在最前：

前两天老大跟我说老虎官网上阿谁自定义头像的功能是flash实现的，没有安装过的还得手动去“允许”falsh的运转。所以让我用canvas实现一个同样的功能，嘿嘿，恰好比来也在研究canvas，所以怅然应允（其实，你没研究过难道就不应允么，哈哈哈哈哈~）

成果展现：

Git地址:https://github.com/ry928330/portraitDIY

功能注明：

拖拽左侧小方框，或者是鼠标放在小方框右下角，点击拉伸方框，方框遮盖局部的图片被主动截取下来，然后再在右边的多个容器里面重绘。
输入宽高，自定义你需要订制的头像大小，当前只支撑宽高雷同的头像图片。

实现细节：

由于你要对图片所在的区域进行截图，所以你得制作一张canvas，盖在图片所在的区域。这里，我们给出了一个函数，依据传入的DOM里面元素的类名新建雷同位置的canvas，盖在本来的DOM元素上面：

function createCanvasByClassName(tag) {
    var canvasInitialWidth = $('.' + tag).width();
    var canvasInitialHeight = $('.' + tag).height();
    var left = $('.' + tag).offset().left - $('.' + tag).parent('.portraitContainer').offset().left + 1;
    var top = $('.' + tag).offset().top - $('.' + tag).parent('.portraitContainer').offset().top + 1;
    //var left = $('.' + tag).offset().left + 1;
    //var top = $('.' + tag).offset().top + 1;
    clearCanvasObj.left = $('.' + tag).offset().left + 1;
    clearCanvasObj.top = $('.' + tag).offset().top + 1;
    // clearCanvasObj.left = left;
    // clearCanvasObj.top = top;
    var canvasElement = $('');
    var randomNum = Math.floor(getRandom(0, 10000));
    clearCanvasObj.canvasId = randomNum;
    canvasElement.attr({
        id: 'canvas',
        width: canvasInitialWidth,
        height: canvasInitialHeight
    });
    canvasElement.css({
        position: 'absolute',
        top: top, 
        left: left
    });
    //$('body').append(canvasElement);
    var appendEle = $('.portraitContainer').append(canvasElement);
    var canvas = document.getElementById('canvas');
    var ctx = canvas.getContext('2d');
    //ctx.fillStyle = "rgba(211,211,216,0.5)";
    ctx.clearRect(0, 0, canvasInitialWidth, canvasInitialHeight);
    ctx.fillStyle = "rgba(0,0,0, 0.4)";
    ctx.fillRect(0, 0, canvasInitialWidth, canvasInitialHeight);
    return canvas;
}

有了这张canvas你就可以在你图片所在区域肆意的操纵了。第一，落整个区域画上一个浅玄色的暗影，然后再擦除初始小方框区域里面的色彩。然后给整个页面增加mousedown，mousemove，mouseup事件，他们所做的功能就跟你在页面中实现一个拖拽的功能相似，这里重点说下mousemove里面做的操纵，代码如下：

function mousemoveFunc(event) {
    /* Act on the event */
    var nowMouseX = event.clientX - clearCanvasObj.left;
    var nowMouseY = event.clientY - clearCanvasObj.top;
    if (nowMouseX >= clearCanvasObj.xStart && nowMouseX <= clearCanvasObj.xStart + clearCanvasObj.width && nowMouseY >= clearCanvasObj.yStart && nowMouseY <= clearCanvasObj.yStart + clearCanvasObj.height) {
        clearCanvasObj.isCanvasArea = true;
        //clearCanvasObj.isRightCorner = false;
        imgContainerCanvas.style.cursor = 'move';
    } else if ((nowMouseX >= clearCanvasObj.xStart + clearCanvasObj.width - 10) && (nowMouseX <= clearCanvasObj.xStart+ clearCanvasObj.width + 10) 
        && (nowMouseY >= clearCanvasObj.yStart + clearCanvasObj.height - 10) && (nowMouseY <= clearCanvasObj.yStart + clearCanvasObj.height + 10)) {
        clearCanvasObj.isCanvasArea = true;
        //clearCanvasObj.beginDraw = false;
        imgContainerCanvas.style.cursor = 'se-resize';
    } 
    else {
        clearCanvasObj.isCanvasArea = false;
        //clearCanvasObj.isRightCorner = false;
        imgContainerCanvas.style.cursor = 'default';
    }
    var outerDomWidth = $(".imgContainer").width();
    var outerDomHeight = $(".imgContainer").height();
    var xDistance = event.clientX - clearCanvasObj.mouseX;
    var yDistance = event.clientY - clearCanvasObj.mouseY;
    //var outerCTX = canvas.getContext('2d');
    //移动小方框
    if (clearCanvasObj.beginDraw && clearCanvasObj.isCanvasArea && !clearCanvasObj.isRightCorner) {
        ry_CTX.fillStyle = clearCanvasObj.color;
        // console.log('1', clearCanvasObj.xStart, clearCanvasObj.yStart)
        ry_CTX.fillRect(clearCanvasObj.xStart, clearCanvasObj.yStart, clearCanvasObj.width, clearCanvasObj.height);
        //outerCTX.fillRect(0, 0, canvas.width, canvas.height);
        clearCanvasObj.xStart += xDistance;
        clearCanvasObj.yStart += yDistance;
        //判断方框是否达到边界
        if (clearCanvasObj.xStart <= 0) {
            clearCanvasObj.xStart = 0;
        }
        if (clearCanvasObj.yStart <= 0) {
            clearCanvasObj.yStart = 0;
        }
        if ((clearCanvasObj.xStart + clearCanvasObj.width) >= outerDomWidth) {
            clearCanvasObj.xStart = outerDomWidth - clearCanvasObj.width;
        }
        if ((clearCanvasObj.yStart + clearCanvasObj.height) >= outerDomHeight) {
            clearCanvasObj.yStart = outerDomHeight - clearCanvasObj.height;
        }
        // console.log('2', clearCanvasObj.xStart, clearCanvasObj.yStart)
        ry_CTX.clearRect(clearCanvasObj.xStart, clearCanvasObj.yStart, clearCanvasObj.width, clearCanvasObj.height);
        produceSmallPic(clearCanvasObj.xStart+clearCanvasObj.left, clearCanvasObj.yStart+clearCanvasObj.top, clearCanvasObj.width, clearCanvasObj.height, imageURL)
        clearCanvasObj.mouseX = event.clientX;
        clearCanvasObj.mouseY = event.clientY;
    }
    //拖拽小方框
    if (clearCanvasObj.isRightCorner) {
        ry_CTX.fillStyle = clearCanvasObj.color;
        ry_CTX.fillRect(clearCanvasObj.xStart, clearCanvasObj.yStart, clearCanvasObj.width, clearCanvasObj.height);
        var realDistance = Math.min(xDistance, yDistance)
        clearCanvasObj.width +=  realDistance;
        clearCanvasObj.height += realDistance;
        //拖动时边界前提的推断
        if (clearCanvasObj.xStart + clearCanvasObj.width >= outerDomWidth) {
            clearCanvasObj.width = outerDomWidth - clearCanvasObj.xStart;
            clearCanvasObj.height = outerDomWidth - clearCanvasObj.xStart;
        }
        if (clearCanvasObj.yStart + clearCanvasObj.height >= outerDomHeight) {
            clearCanvasObj.width = outerDomHeight - clearCanvasObj.yStart;
            clearCanvasObj.height = outerDomHeight - clearCanvasObj.yStart;
        }
        if (clearCanvasObj.width <= 10) {
            clearCanvasObj.width = 10;
        }
        if (clearCanvasObj.height <= 10) {
            clearCanvasObj.height = 10;
        }
        ry_CTX.clearRect(clearCanvasObj.xStart, clearCanvasObj.yStart, clearCanvasObj.width, clearCanvasObj.height);
        produceSmallPic(clearCanvasObj.xStart+clearCanvasObj.left, clearCanvasObj.yStart+clearCanvasObj.top, clearCanvasObj.width, clearCanvasObj.height, imageURL);
        clearCanvasObj.mouseX = event.clientX;
        clearCanvasObj.mouseY = event.clientY;
    }                            
}

函数里面，你需要注意拖拽的边界前提，一个是方框不克不及拖到图片所在DOM外的边界；别的一个就是当你鼠标放在小方框所在的区域转变鼠标的样式。方框在拖动的历程中，我们一直重绘方框挪移的区域（也就是一直的画上暗影），然后在新的位置调取clearRect函数，从新擦出一个小方框出来。在拖拽或是拉伸的历程中，我们会一直调取produceSmallPic函数，在右侧的容器（每个容器都是一个canvas）里面一直依据容器大小重绘出所需的头像。代码如下：

function produceSmallPic(imageURL,left, top, width, height) {
    var img = new Image();
    img.src = imageURL;
    var targetCtx = new Array();
    var targetCanvas = null;
    img.onload = function() {
        portraitGroupsArr.forEach(function(item, index) {
            targetCanvas = document.getElementById(item.class);
            targetCtx.push(targetCanvas.getContext('2d'));
            targetCtx[index].clearRect(0,0, item.width, item.height);
            targetCtx[index].drawImage(img, left - clearCanvasObj.left, top - clearCanvasObj.top, width, height, 0, 0 , item.width, item.height);
        })
    }
}

我们说下这个函数的作用，这里我们要注意一个参数imageURL，这个URL是由图片所在的DOM转化来的。由于你要把DOM所在的区域酿成一张图片，这样你才干在应用drawImage函数截取你所需要的区域。所以我们先应用html2canvas库函数讲图片所在的DOM转化为canvas，这张canvas的内容是包括你所要截取的图片的，然后把这张canvas转化为图片取得图片地址imageURL，代码如下：

html2canvas(document.getElementById('imgContainer'), {
        onrendered: function(canvas) {
            var imageURL = canvasTransToImage(canavs);
            ...
        }
})
function canvasTransToImage(canvas) {
    var imageURL = canvas.toDataURL('image/png');
    return imageURL;
}

接着，你就可以便捷右边的canvas容器，讲图片重回到里面了，整个历程就这样完毕，回首看来是不是很简略。

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