Javascript 从画布获取图像维度
我有一个612x300px的画布画板。如果我在它里面画一些东西,然后用Javascript 从画布获取图像维度,javascript,canvas,Javascript,Canvas,我有一个612x300px的画布画板。如果我在它里面画一些东西,然后用toDataURL()得到图像,我会得到一个612x300px的图像,但我只想要没有背景的部分。我不知道该怎么从这个开始 可以这样做吗?[编辑以反映新信息] 下面是如何提取用户绘制的图片部分 下面是代码和小提琴: 正文{背景色:象牙;} #容器{位置:相对;边距:15px;} 画布{边框:1px纯红色;位置:绝对;顶部:0;左侧:0;} #草图{位置:绝对;顶部:315px;左侧:0px;} #结果{边框:1px纯绿色;位置
toDataURL()
得到图像,我会得到一个612x300px的图像,但我只想要没有背景的部分。我不知道该怎么从这个开始
可以这样做吗?[编辑以反映新信息] 下面是如何提取用户绘制的图片部分 下面是代码和小提琴:
正文{背景色:象牙;}
#容器{位置:相对;边距:15px;}
画布{边框:1px纯红色;位置:绝对;顶部:0;左侧:0;}
#草图{位置:绝对;顶部:315px;左侧:0px;}
#结果{边框:1px纯绿色;位置:绝对;顶部:350px;左侧:0px;}
$(函数(){
var canvas=document.getElementById(“canvas”);
var ctx=canvas.getContext(“2d”);
var background=document.getElementById(“背景”);
var bkCtx=background.getContext(“2d”);
var lastX;
血管成形术;
var strokeColor=“红色”;
var strokeWidth=2;
canMouseX变种;
var canMouseY;
var canvasOffset=$(“#画布”).offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var isMouseDown=错误;
var-top=10000;
左var=10000;
var-right=0;
var-bottom=0;
//画背景
var计数=0;
var半径=15;
var d=半径*2
bkCtx.strokeStyle=“橙色”;
bkCtx.线宽=1;
bkCtx.fillStyle=“蓝色”;
对于(变量y=0;y
正文{背景色:象牙;}
画布{边框:1px纯红色;位置:绝对;顶部:0;左侧:0;}
#包装{左边距:150px;}
#结果{边框:1px纯绿色;位置:绝对;顶部:0;左侧:300px;}
按钮{位置:绝对;顶部:275px;左侧:0;}
$(函数(){
var canvas=document.getElementById(“canvas”);
var ctx=canvas.getContext(“2d”);
var lastX;
血管成形术;
var strokeColor=“红色”;
var strokeWidth=2;
canMouseX变种;
var canMouseY;
var canvasOffset=$(“#画布”).offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var isMouseDown=错误;
//加载背景图像并将画布设置为相同大小
var img=新图像();
img.onload=函数(){
var background=document.getElementById(“背景”);
var bkCtx=background.getContext(“2d”);
背景宽度=img.width;
背景高度=img高度;
bkCtx.drawImage(img,0,0);
canvas.width=img.width;
canvas.height=img.height;
var results=document.getElementById(“结果”);
结果:宽度=img.width;
结果:高度=img高度;
控制台日志(img);
}
img.src=”http://dl.dropbox.com/u/139992952/stackoverflow/house-icon.png";
功能手柄向下(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
$(“#downlog”).html(“Down:“+canMouseX+”/“+canMouseY”);
//把你的鼠标下的东西放在这里
lastX=canMouseX;
拉斯蒂=坎穆西;
isMouseDown=真;
}
功能handleMouseUp(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
$(“#uplog”).html(“Up:“+canMouseX+”/“+canMouseY”);
//把你的鼠标放在这里
isMouseDown=错误;
}
函数handleMouseOut(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
$(“#outlog”).html(“Out:+canMouseX+”/“+canMouseY);
//把你的老鼠屎放在这里
isMouseDown=错误;
}
功能手柄移动(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
$(“#movelog”).html(“移动:+canMouseX+”/“+canMouseY”);
//把你的mousemove放在这里
如果(isMouseDown){
ctx.beginPath();
ctx.moveTo(lastX,lastY);
ctx.lineTo(canMouseX,canMouseY);
ctx.stroke();
lastX=canMouseX;
拉斯蒂=坎穆西;
}
}
函数提取(){
var results=document.getElementById(“结果”);
results.src=canvas.toDataURL();
警报(“正常”);
}
$(“#canvas”).mousedown(函数(e){handleMouseDown(e);});
$(“#canvas”).mousemove(函数(e){handleMouseMove(e);});
$(“#canvas”).mouseup(函数(e){handleMouseUp(e);});
$(“#canvas”).mouseout(函数(e){handleMouseOut(e);});
$(“#草图”)。单击(函数(e){extract(e);});
});//end$(函数(){});
提取草图
toDataURL方法始终返回整个图像的数据。如果您只需要图像的一部分,则必须创建该大小的新画布元素,并将图像数据复制到正确的位置。是的,但我没有绘制的尺寸。例如,如果我用鼠标绘制一个圆,我需要获得o只有新图像上的圆圈…可能通过删除白色背景?我可以使用服务器端或客户端。如果你“用鼠标绘制”,那么你应该能够捕捉到坐标。谢谢你的回答,但我想我解释得不好。我需要去除背景并裁剪颜料,而不是整个画布。所以如果我有612x300画布,并在画布的任何位置绘制1x10px水平线,我需要得到1x10px图像,而不是612x300。好的,我现在明白了.一个问题:如果你在一个X上画两条线,你想要包含X的正方形还是只想要X的两条线?这正是我需要的!!谢谢
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<!--[if lt IE 9]><script type="text/javascript" src="../excanvas.js"></script><![endif]-->
<style>
body{ background-color: ivory;}
#container{position:relative; margin:15px;}
canvas{border:1px solid red; position:absolute; top:0; left:0;}
#sketch{position:absolute; top:315px; left:0px;}
#results{border:1px solid green; position:absolute; top:350px; left:0px;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var background=document.getElementById("background");
var bkCtx=background.getContext("2d");
var lastX;
var lastY;
var strokeColor="red";
var strokeWidth=2;
var canMouseX;
var canMouseY;
var canvasOffset=$("#canvas").offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var isMouseDown=false;
var top=10000;
var left=10000;
var right=0;
var bottom=0;
// draw the background
var count=0;
var radius=15;
var d=radius*2
bkCtx.strokeStyle="orange";
bkCtx.lineWidth=1;
bkCtx.fillStyle="blue";
for(var y=0;y<10;y++){
for(var x=0;x<10;x++){
count++;
bkCtx.beginPath();
bkCtx.rect(x*30,y*30,30,30);
//bkCtx.arc(x+radius, y+radius, radius, 0 , 2 * Math.PI, false);
bkCtx.fillText(count,x*30+9,y*30+15);
bkCtx.stroke();
console.log(y);
}
}
function handleMouseDown(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
// Put your mousedown stuff here
lastX=canMouseX;
lastY=canMouseY;
isMouseDown=true;
}
function handleMouseUp(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
// Put your mouseup stuff here
isMouseDown=false;
}
function handleMouseOut(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
// Put your mouseOut stuff here
isMouseDown=false;
}
function handleMouseMove(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
// Put your mousemove stuff here
if(isMouseDown){
ctx.beginPath();
ctx.moveTo(lastX,lastY);
ctx.lineTo(canMouseX,canMouseY);
ctx.stroke();
lastX=canMouseX;
lastY=canMouseY;
// define the bounding box of all drawings
if(canMouseX<left){left=canMouseX;}
if(canMouseX>right){right=canMouseX;}
if(canMouseY<top){top=canMouseY;}
if(canMouseY>bottom){bottom=canMouseY;}
}
}
function capture(e){
var imageData=bkCtx.getImageData(left,top,right-left,bottom-top);
var temp=document.createElement("canvas");
var tempCtx=temp.getContext("2d");
temp.width=right-left;
temp.height=bottom-top;
tempCtx.putImageData(imageData,0,0);
var results=document.getElementById("results");
results.src=temp.toDataURL();
console.log(left+"/"+top+" -- "+right+"/"+bottom);
}
$("#canvas").mousedown(function(e){handleMouseDown(e);});
$("#canvas").mousemove(function(e){handleMouseMove(e);});
$("#canvas").mouseup(function(e){handleMouseUp(e);});
$("#canvas").mouseout(function(e){handleMouseOut(e);});
$("#sketch").click(function(e){capture(e);});
}); // end $(function(){});
</script>
</head>
<body>
<p>Drag to select an area to extract</p>
<div id="container">
<canvas id="background" width=300 height=300></canvas>
<canvas id="canvas" width=300 height=300></canvas>
<button id="sketch">Extract the sketch area</button>
<img id="results">
</div>
</body>
</html>
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<!--[if lt IE 9]><script type="text/javascript" src="../excanvas.js"></script><![endif]-->
<style>
body{ background-color: ivory; }
canvas{border:1px solid red; position:absolute; top:0; left:0;}
#wrapper{left-margin:150px;}
#results{border:1px solid green; position:absolute; top:0; left:300px;}
button{position:absolute; top:275px; left:0;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var lastX;
var lastY;
var strokeColor="red";
var strokeWidth=2;
var canMouseX;
var canMouseY;
var canvasOffset=$("#canvas").offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var isMouseDown=false;
// load the background image and set the canvas to the same size
var img=new Image();
img.onload=function(){
var background=document.getElementById("background");
var bkCtx=background.getContext("2d");
background.width=img.width;
background.height=img.height;
bkCtx.drawImage(img,0,0);
canvas.width=img.width;
canvas.height=img.height;
var results=document.getElementById("results");
results.width=img.width;
results.height=img.height;
console.log(img);
}
img.src="http://dl.dropbox.com/u/139992952/stackoverflow/house-icon.png";
function handleMouseDown(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
$("#downlog").html("Down: "+ canMouseX + " / " + canMouseY);
// Put your mousedown stuff here
lastX=canMouseX;
lastY=canMouseY;
isMouseDown=true;
}
function handleMouseUp(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
$("#uplog").html("Up: "+ canMouseX + " / " + canMouseY);
// Put your mouseup stuff here
isMouseDown=false;
}
function handleMouseOut(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
$("#outlog").html("Out: "+ canMouseX + " / " + canMouseY);
// Put your mouseOut stuff here
isMouseDown=false;
}
function handleMouseMove(e){
canMouseX=parseInt(e.clientX-offsetX);
canMouseY=parseInt(e.clientY-offsetY);
$("#movelog").html("Move: "+ canMouseX + " / " + canMouseY);
// Put your mousemove stuff here
if(isMouseDown){
ctx.beginPath();
ctx.moveTo(lastX,lastY);
ctx.lineTo(canMouseX,canMouseY);
ctx.stroke();
lastX=canMouseX;
lastY=canMouseY;
}
}
function extract(){
var results=document.getElementById("results");
results.src=canvas.toDataURL();
alert("ok");
}
$("#canvas").mousedown(function(e){handleMouseDown(e);});
$("#canvas").mousemove(function(e){handleMouseMove(e);});
$("#canvas").mouseup(function(e){handleMouseUp(e);});
$("#canvas").mouseout(function(e){handleMouseOut(e);});
$("#sketch").click(function(e){extract(e);});
}); // end $(function(){});
</script>
</head>
<body>
<canvas id="background" width=100 height=100></canvas>
<canvas id="canvas" width=100 height=100></canvas>
<button id="sketch">Extract the sketch</button>
<img id="results" width=10 height=10>
</body>
</html>