如何讓用戶在純Javascript中將剪貼板中的圖像數據粘貼到Firefox中的canvas元素中?



html5 (1)

版本2.0 :更小,更清晰的代碼適用於Chrome,Firefox,Edge,Opera。 沒有更多的黑客。 但如果您需要支持IE和Safari,請檢查v1版本。

http://jsfiddle.net/KJW4E/905/

1.0版 Chrome實現很簡單。 Firefox(和IE)有一些限制,用戶必須給命令做粘貼,如鍵盤事件和可編輯輸入必須集中,所以我們在這裡做技巧 - 在ctrl下我們focusthat輸入字段,釋放unocus。

瀏覽器支持 (圖像數據):

  • 火狐
  • 邊緣
  • IE-11
  • 歌劇

var CLIPBOARD = new CLIPBOARD_CLASS("my_canvas", true);

/**
 * image pasting into canvas
 * 
 * @param {string} canvas_id - canvas id
 * @param {boolean} autoresize - if canvas will be resized
 */
function CLIPBOARD_CLASS(canvas_id, autoresize) {
	var _self = this;
	var canvas = document.getElementById(canvas_id);
	var ctx = document.getElementById(canvas_id).getContext("2d");
	var ctrl_pressed = false;
	var command_pressed = false;
	var paste_event_support;
	var pasteCatcher;

	//handlers
	document.addEventListener('keydown', function (e) {
		_self.on_keyboard_action(e);
	}, false); //firefox fix
	document.addEventListener('keyup', function (e) {
		_self.on_keyboardup_action(e);
	}, false); //firefox fix
	document.addEventListener('paste', function (e) {
		_self.paste_auto(e);
	}, false); //official paste handler

	//constructor - we ignore security checks here
	this.init = function () {
		pasteCatcher = document.createElement("div");
		pasteCatcher.setAttribute("id", "paste_ff");
		pasteCatcher.setAttribute("contenteditable", "");
		pasteCatcher.style.cssText = 'opacity:0;position:fixed;top:0px;left:0px;width:10px;margin-left:-20px;';
		document.body.appendChild(pasteCatcher);

		// create an observer instance
		var observer = new MutationObserver(function(mutations) {
			mutations.forEach(function(mutation) {
				if (paste_event_support === true || ctrl_pressed == false || mutation.type != 'childList'){
					//we already got data in paste_auto()
					return true;
				}

				//if paste handle failed - capture pasted object manually
				if(mutation.addedNodes.length == 1) {
					if (mutation.addedNodes[0].src != undefined) {
						//image
						_self.paste_createImage(mutation.addedNodes[0].src);
					}
					//register cleanup after some time.
					setTimeout(function () {
						pasteCatcher.innerHTML = '';
					}, 20);
				}
			});
		});
		var target = document.getElementById('paste_ff');
		var config = { attributes: true, childList: true, characterData: true };
		observer.observe(target, config);
	}();
	//default paste action
	this.paste_auto = function (e) {
		paste_event_support = false;
		if(pasteCatcher != undefined){
			pasteCatcher.innerHTML = '';
		}
		if (e.clipboardData) {
			var items = e.clipboardData.items;
			if (items) {
				paste_event_support = true;
				//access data directly
				for (var i = 0; i < items.length; i++) {
					if (items[i].type.indexOf("image") !== -1) {
						//image
						var blob = items[i].getAsFile();
						var URLObj = window.URL || window.webkitURL;
						var source = URLObj.createObjectURL(blob);
						this.paste_createImage(source);
					}
				}
				e.preventDefault();
			}
			else {
				//wait for DOMSubtreeModified event
				//https://bugzilla.mozilla.org/show_bug.cgi?id=891247
			}
		}
	};
	//on keyboard press
	this.on_keyboard_action = function (event) {
		k = event.keyCode;
		//ctrl
		if (k == 17 || event.metaKey || event.ctrlKey) {
			if (ctrl_pressed == false)
				ctrl_pressed = true;
		}
		//v
		if (k == 86) {
			if (document.activeElement != undefined && document.activeElement.type == 'text') {
				//let user paste into some input
				return false;
			}

			if (ctrl_pressed == true && pasteCatcher != undefined){
				pasteCatcher.focus();
			}
		}
	};
	//on kaybord release
	this.on_keyboardup_action = function (event) {
		//ctrl
		if (event.ctrlKey == false && ctrl_pressed == true) {
			ctrl_pressed = false;
		}
		//command
		else if(event.metaKey == false && command_pressed == true){
			command_pressed = false;
			ctrl_pressed = false;
		}
	};
	//draw pasted image to canvas
	this.paste_createImage = function (source) {
		var pastedImage = new Image();
		pastedImage.onload = function () {
			if(autoresize == true){
				//resize
				canvas.width = pastedImage.width;
				canvas.height = pastedImage.height;
			}
			else{
				//clear canvas
				ctx.clearRect(0, 0, canvas.width, canvas.height);
			}
			ctx.drawImage(pastedImage, 0, 0);
		};
		pastedImage.src = source;
	};
}
1. Copy image data into clipboard or press Print Screen <br>
2. Press Ctrl+V (page/iframe must be focused):
<br /><br />
<canvas style="border:1px solid grey;" id="my_canvas" width="300" height="300"></canvas>

我已經盡力找到一個簡單,相關,最新的示例,適用於最新版本的Firefox,我真的很掙扎。

標題說這一切都是真的。 我希望用戶能夠從Windows Paint等編輯器複製部分圖像,或使用“打印屏幕”按鈕,然後將其粘貼到畫布元素中。 如果畫布調整大小以完全適合粘貼的圖像(字面意思),則為獎勵點。

如果合理,要避免使用基於Flash或Java的解決方案。

我在Javascript方面還不錯,但是對於最新的HTML5功能相對缺乏經驗,而且對Canvas元素來說是全新的。 請幫忙!





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