drag-and-drop - 使用 fabric.js 将图像从 pc(用户系统)拖放到 Canvas

Question

嘿，我正在做一个项目，我需要使用 fabric.js 将图像从 PC(用户系统)拖放到 html5 canvas，因为我得到了 div(作为下拉列表)到 canvas 的代码，但被 PC 击中了(用户系统) Canvas 任何人都可以帮助我如何进一步进行。

这是我到目前为止完成的代码

 var js_c_drawing, activeObject = null;
        $(document).ready(function () {
            setDrawingCanvasCoords();
            js_c_drawing = new fabric.Canvas('c_drawing');
            js_c_drawing.calcOffset();
            if (typeof fabric.instances != "undefined") fabric.instances.push(js_c_drawing);
        });
        function setDrawingCanvasCoords() {
            var wHeight = $(window).height() - 100;
            var wWidth = $(window).width() - 164;
            var drawingStyle = 'border:4px solid gray;top:20px;position:relative;background-color:black;' + 'width:' + wWidth + 'px; height:' + wHeight + 'px';
            $("#divDrawing").attr('style', drawingStyle);
        }       
        function showToolMenu(shapeMenu) {
            var divShapesId = 'divShapes';
            var divElement = $('#' + divShapesId);
            var ele = document.getElementById('a' + shapeMenu);
            elePosition = findPos(ele);
            document.getElementById(divShapesId).style.left = elePosition[0] + 'px';
            document.getElementById(divShapesId).style.top = elePosition[1] + (ele.offsetHeight) + 'px';
            document.getElementById(divShapesId).style.zIndex = 100;
            divElement.show();
            var url = baseurl + shapeMenu;
            $(divElement).load(url);
        }
        function hideToolMenu() {
            var divShapesId = 'divShapes';
            var divElement = $('#' + divShapesId);
            document.getElementById(divShapesId).style.zIndex = 20;
            divElement.hide(2000);
        }   
        function findPos(obj) {
            var curleft = curtop = 0;
            if (obj.offsetParent) {
                curleft = obj.offsetLeft
                curtop = obj.offsetTop
                while (obj = obj.offsetParent) {
                    curleft += obj.offsetLeft
                    curtop += obj.offsetTop
                }

            }
            return [curleft, curtop];
        }

我已经尝试使用 http://www.html5rocks.com/en/tutorials/file/dndfiles/这但它显示图像大小等，我已经尝试过http://jsfiddle.net/natchiketa/w8kkc/此代码与 PC(用户系统)和 Canvas 有关，但未成功。

Answer 1

终于找到了解决方案http://jsfiddle.net/rodrigopandini/gj7HT/使用以上两个链接。这是代码

function handleDragStart(e) {
    [].forEach.call(images, function (img) {
        img.classList.remove('img_dragging');
    });
    this.classList.add('img_dragging');
}

function handleDragOver(e) {
    if (e.preventDefault) {
        e.preventDefault(); // Necessary. Allows us to drop.
    }

    e.dataTransfer.dropEffect = 'copy'; // See the section on the DataTransfer object.
    // NOTE: comment above refers to the article (see top) -natchiketa

    return false;
}

function handleDragEnter(e) {
    // this / e.target is the current hover target.
    this.classList.add('over');
}

function handleDragLeave(e) {
    this.classList.remove('over'); // this / e.target is previous target element.
}

function handleDrop(e) {    
    // this / e.target is current target element.

    /*
    if (e.stopPropagation) {
        e.stopPropagation(); // stops the browser from redirecting.
    }
    */

    e.stopPropagation(); // Stops some browsers from redirecting.
    e.preventDefault(); // Stops some browsers from redirecting.

    // handle desktop images
    if(e.dataTransfer.files.length > 0){

        var files = e.dataTransfer.files;
        for (var i = 0, f; f = files[i]; i++) {

            // Only process image files.
            if (f.type.match('image.*')) {            
                // Read the File objects in this FileList.
                var reader = new FileReader();
                // listener for the onload event
                reader.onload = function(evt) {
                    // create img element
                    var img = document.createElement('img');
                    img.src= evt.target.result;                        

                    // put image on canvas
                    var newImage = new fabric.Image(img, {
                        width: img.width,
                        height: img.height,
                        // Set the center of the new object based on the event coordinates relative to the canvas container.
                        left: e.layerX,
                        top: e.layerY
                    });
                    canvas.add(newImage);
                };
               // Read in the image file as a data URL.
               reader.readAsDataURL(f);
            }
        }
    }  
    // handle browser images
    else{        
       var img = document.querySelector('#images img.img_dragging');
        var newImage = new fabric.Image(img, {
            width: img.width,
            height: img.height,
            // Set the center of the new object based on the event coordinates relative to the canvas container.
            left: e.layerX,
            top: e.layerY
        });
        canvas.add(newImage); 
    } 

    return false;
}

function handleDragEnd(e) {
    // this/e.target is the source node.
    [].forEach.call(images, function (img) {
        img.classList.remove('img_dragging');
    });
}

if (Modernizr.draganddrop) {
    // Browser supports HTML5 DnD.

    // Bind the event listeners for the image elements
    var images = document.querySelectorAll('#images img');
    [].forEach.call(images, function (img) {
        img.addEventListener('dragstart', handleDragStart, false);
        img.addEventListener('dragend', handleDragEnd, false);
    });
    // Bind the event listeners for the canvas
    var canvasContainer = document.getElementById('canvas-container');
    canvasContainer.addEventListener('dragenter', handleDragEnter, false);
    canvasContainer.addEventListener('dragover', handleDragOver, false);
    canvasContainer.addEventListener('dragleave', handleDragLeave, false);
    canvasContainer.addEventListener('drop', handleDrop, false);
} else {
    // Replace with a fallback to a library solution.
    alert("This browser doesn't support the HTML5 Drag and Drop API.");
}