尝试使用HTML5文件系统将画布PNG数据URL保存到磁盘,但是当我作为URL检索时,它无效 [英] Trying to save canvas PNG data url to disk with HTML5 filesystem, but when I retrieve as URL, it's invalid
问题描述
我从画布获得base64编码的图像:
I get the base64-encoded image form the canvas as:
var dataURL = canvas.toDataURL( "image/png" );
然后我把它变成这样的数据:
Then I turn it into data like this:
//Remove the beginning identifier and use Chrome/Firefox?safari built int base64Decoder
var data = atob( dataURL.substring( "data:image/png;base64,".length ) );
然后我通过以下方式将其写入文件系统:
Then I write it to the filesystem via:
event.createWriter(
function(writerEvent)
{
//The success handler
writerEvent.onwriteend = function(finishEvent)
{
...
};
//Error handler
writerEvent.onerror = settings.error;
// Create a new Blob
var blob = new Blob( [ data ], { type: "image/png" } );
//Write it into the path
writerEvent.write( blob );
}
}
我尝试设置它作为这样的图像的src:
I try to set it as src of an image like this:
document.getElementById( "saved" ).src = event.toURL();
写入文件,我能够找到并获取网址(通过阅读和使用事件: event.toURL()
。但图片显示为网页上的图片图标。我该怎么办错了?
That writes the file and I am able to find it and get a url (by reading it and using the event: event.toURL()
. But the image shows as a broken image icon on the web page. What am I doing wrong?
推荐答案
数据
是一个字符串,所以当你通过它为blob,二进制数据将是UTF-8编码的字符串。你想要
二进制数据而不是字符串。
data
is a string, so when you pass it to blob, the binary data will be that string in UTF-8 encoding. You want
binary data not a string.
你可以这样做:
var canvas = document.createElement("canvas");
var dataURL = canvas.toDataURL( "image/png" );
var data = atob( dataURL.substring( "data:image/png;base64,".length ) ),
asArray = new Uint8Array(data.length);
for( var i = 0, len = data.length; i < len; ++i ) {
asArray[i] = data.charCodeAt(i);
}
var blob = new Blob( [ asArray.buffer ], {type: "image/png"} );
还有 canvas.toBlob
未来但目前不在Chrome中。
There is also canvas.toBlob
available in future but not currently in Chrome.
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