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div和canvas的问题_html/css_WEB-ITnose
- WBOYoriginal
- 2016-06-21 09:28:331290parcourir
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" ><head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>图片上传本地预览</title> <style type="text/css">#preview{width:260px;height:190px;border:1px solid #000;overflow:hidden;}#imghead {filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);}</style><script type="text/javascript"> //图片上传预览 IE是用了滤镜。 function previewImage(file) { var MAXWIDTH = 260; var MAXHEIGHT = 180; var div = document.getElementById('preview'); if (file.files && file.files[0]) { div.innerHTML ='<img id=imghead alt="div和canvas的问题_html/css_WEB-ITnose" >'; var img = document.getElementById('imghead'); img.onload = function(){ var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight); img.width = rect.width; img.height = rect.height;// img.style.marginLeft = rect.left+'px'; img.style.marginTop = rect.top+'px'; } var reader = new FileReader(); reader.onload = function(evt){img.src = evt.target.result;} reader.readAsDataURL(file.files[0]); } else //兼容IE { var sFilter='filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="'; file.select(); var src = document.selection.createRange().text; div.innerHTML = '<img id=imghead alt="div和canvas的问题_html/css_WEB-ITnose" >'; var img = document.getElementById('imghead'); img.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src = src; var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight); status =('rect:'+rect.top+','+rect.left+','+rect.width+','+rect.height); div.innerHTML = "<div id=divhead style="max-width:90%"+rect.width+"px;height:"+rect.height+"px;margin-top:"+rect.top+"px;"+sFilter+src+"\"'></div>"; } } function clacImgZoomParam( maxWidth, maxHeight, width, height ){ var param = {top:0, left:0, width:width, height:height}; if( width>maxWidth || height>maxHeight ) { rateWidth = width / maxWidth; rateHeight = height / maxHeight; if( rateWidth > rateHeight ) { param.width = maxWidth; param.height = Math.round(height / rateWidth); }else { param.width = Math.round(width / rateHeight); param.height = maxHeight; } } param.left = Math.round((maxWidth - param.width) / 2); param.top = Math.round((maxHeight - param.height) / 2); return param; }</script> </head> <body><div id="preview"> <img id="imghead" style="max-width:90%"<%=request.getContextPath()% alt="div和canvas的问题_html/css_WEB-ITnose" >/images/defaul.jpg'></div> <input type="file" onchange="previewImage(this)" /> </body> </html> 这是我网上看到的网页上传图片的代码，试了一下把：
中的div改成了画布，功能就无效了。不能改成canvas吗？为什么呢
应该是可以改的，大神们怎么改呢
回复讨论(解决方案)
你的浏览器不支持？IE版本是多少
canvas要用drawImage方法把图片渲染出来
是从本地选一张图片显示到网页上 div中可以显示 ，改成canvas就不行啦，我知道图形是脚本画的来
canvas要用drawImage方法把图片渲染出来
能把代码贴出来吗 谢谢
canvas要用drawImage方法把图片渲染出来
能把代码贴出来吗 谢谢
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" > <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>图片上传本地预览</title> <style type="text/css">#preview{width:260px;height:190px;border:1px solid #000;overflow:hidden;}#imghead {filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);}</style><script type="text/javascript"> //图片上传预览 IE是用了滤镜。 function previewImage(file) { var MAXWIDTH = 260; var MAXHEIGHT = 180; var div = document.getElementById('preview'); if (file.files && file.files[0]) { var reader = new FileReader(); reader.onload = function(evt){ canvasPreview(evt.target.result); } reader.readAsDataURL(file.files[0]); } else //兼容IE { var sFilter='filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="'; file.select(); var src = document.selection.createRange().text; div.innerHTML = '<img id=imghead alt="div和canvas的问题_html/css_WEB-ITnose" >'; var img = document.getElementById('imghead'); img.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src = src; var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight); status =('rect:'+rect.top+','+rect.left+','+rect.width+','+rect.height); div.innerHTML = "<div id=divhead style="max-width:90%"+rect.width+"px;height:"+rect.height+"px;margin-top:"+rect.top+"px;"+sFilter+src+"\"'></div>"; } } function canvasPreview(url){ var image = new Image(); image.src = url; image.onload = function(){ var canvas = document.getElementById('canvas'); var context = canvas.getContext('2d'); context.drawImage(this,0,0); } } function clacImgZoomParam( maxWidth, maxHeight, width, height ){ var param = {top:0, left:0, width:width, height:height}; if( width>maxWidth || height>maxHeight ) { rateWidth = width / maxWidth; rateHeight = height / maxHeight; if( rateWidth > rateHeight ) { param.width = maxWidth; param.height = Math.round(height / rateWidth); }else { param.width = Math.round(width / rateHeight); param.height = maxHeight; } } param.left = Math.round((maxWidth - param.width) / 2); param.top = Math.round((maxHeight - param.height) / 2); return param; }</script> </head> <body><div id="preview"> <img id="imghead" style="max-width:90%"<%=request.getContextPath()% alt="div和canvas的问题_html/css_WEB-ITnose" >/images/defaul.jpg'></div><canvas id="canvas" width="500px" height="500px"> </canvas> <input type="file" onchange="previewImage(this)" /> </body> </html> Déclaration：
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