How to do Copy and paste the image from User system to Canvas using fabric.js

问题

Can we do copy(Ctrl+C) and paste(Ctrl+V) the image from User system(desktop/any folder) to canvas using fabric.js. I have seen the copy and paste program inside the canvas, I have found this Example while searching google but didnt find any relevant example for desktop to canvas. Here is the snippet for copy and paste

function onKeyDownHandler(event) {
    //event.preventDefault();

    var key;
    if(window.event){
        key = window.event.keyCode;
    }
    else{
        key = event.keyCode;
    }

    switch(key){
        //////////////
        // Shortcuts
        //////////////
        // Copy (Ctrl+C)
        case 67: // Ctrl+C
            if(ableToShortcut()){
                if(event.ctrlKey){
                    event.preventDefault();
                    copy();
                }
            }
            break;
        // Paste (Ctrl+V)
        case 86: // Ctrl+V
            if(ableToShortcut()){
                if(event.ctrlKey){
                    event.preventDefault();
                    paste();
                }
            }
            break;            
        default:
            // TODO
            break;
    }
}


function ableToShortcut(){
    /*
    TODO check all cases for this

    if($("textarea").is(":focus")){
        return false;
    }
    if($(":text").is(":focus")){
        return false;
    }
    */
    return true;
}

function copy(){
    if(canvas.getActiveGroup()){
        for(var i in canvas.getActiveGroup().objects){
            var object = fabric.util.object.clone(canvas.getActiveGroup().objects[i]);
            object.set("top", object.top+5);
            object.set("left", object.left+5);
            copiedObjects[i] = object;
        }                    
    }
    else if(canvas.getActiveObject()){
        var object = fabric.util.object.clone(canvas.getActiveObject());
        object.set("top", object.top+5);
        object.set("left", object.left+5);
        copiedObject = object;
        copiedObjects = new Array();
    }
}

function paste(){
    if(copiedObjects.length > 0){
        for(var i in copiedObjects){
            canvas.add(copiedObjects[i]);
        }                    
    }
    else if(copiedObject){
        canvas.add(copiedObject);
    }
    canvas.renderAll();    
}

Is it possible to do actually I have heard dat it's may not possible.Can anyone guide me how to do please.

回答1:

If you're targeting modern browsers you can combine 2 new (but widely adopted) html5 features to accomplish your task:

You can create a dropzone on your page using the dragover and drop events.
Then you can use the FileReader API to read the image files into an image object.
Then it's back to FabricJS to load the image as usual.

Here's a tutorial describing how to do the hard bits (#1,#2): http://www.html5rocks.com/en/tutorials/file/dndfiles/

[ Added code that SOMETIMES allows cut/paste of image files ]

Most modern browsers support binding the “paste” event.

// listen for the paste event
window.addEventListener("paste",pasteImage);

But...!!

Support for non-text mime types (ie “image”) is scarce. Chrome seems to support it “off-and-on”.

…And browsers are constantly revising their cut/paste capabilities because of security concerns.

Here is code that sometimes works in Chrome.

// listen for the paste event
window.addEventListener("paste",pasteImage);

function pasteImage(event) {

    // get the raw clipboardData
    var cbData=event.clipboardData;

    for(var i=0;i<cbData.items.length;i++){

        // get the clipboard item
        var cbDataItem = cbData.items[i];
        var type = cbDataItem.type;

        // warning: most browsers don't support image data type
        if (type.indexOf("image")!=-1) {
            // grab the imageData (as a blob)
            var imageData = cbDataItem.getAsFile();
            // format the imageData into a URL
            var imageURL=window.webkitURL.createObjectURL(imageData);
            // We've got an imageURL, add code to use it as needed
            // the imageURL can be used as src for an Image object
        }
    }
}

来源：https://stackoverflow.com/questions/17182778/how-to-do-copy-and-paste-the-image-from-user-system-to-canvas-using-fabric-js

标签

html5-canvas

fabricjs