filereader | 易学教程

ocrad.js- OCR Javascript Library throwing Uncaught SecurityError on passing HTML5 canvas to OCRAD() API

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问题 I'm a newbie in HTML5+JS, I want to develop an hybrid app using ocrad.js . The code given below , downloaded from github page is perfectly working for me(Chrome 32.0.1). <html> <head> </head> <body> <script src="../ocrad.js"></script> <script> function OCRImage(image){ var canvas = document.createElement('canvas') canvas.width = image.naturalWidth; canvas.height = image.naturalHeight; canvas.getContext('2d').drawImage(image, 0, 0) return OCRAD(canvas) } function OCRPath(url, callback){ var

Loading CSV with FileReader to make JS Objects for Map Markers (Maps API)

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问题 Basically I'm trying to load a csv file, parse it to an array of js objects and use those objects to make map markers with the Google Maps API. The loading works, the parsing works, all the values are correct (to my knowledge), I've been console logging to death and I get the values that I want but... my map isn't loading. I think it may be because of timing? Like the map isn't initializing or being loaded correctly. I occasionally get errors about connections timing out and security errors

Do ArrayBuffers have a maximum length?

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问题 I little confused here. Do ArrayBuffer allocate a new memory region for it? If so, what would be the safe maximum Blob size to put on it? 回答1: That only depends on your system and there doesn't seems to be a limit. According to the specification : If the requested number of bytes could not be allocated an exception is raised. 回答2: what would be the safe maximum Blob size to put on it There does not seem to be a hard limit, just whatever restrictions your platform imposes. However, if one uses

Java: How do you read each line of a text file and setting each line as an array element?

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问题 I am trying to read questions that are listed in each line of a text file and then adding each line to an array, so that they can be called individually later on. I'm almost positive it is possible to do in Java but I am unsure how to do it. I did figure out how to read a whole text file and setting it all to a string: private static String readFile(String pathname) { String line = null; try { BufferedReader reader = new BufferedReader(new FileReader(pathname)); while((line = reader.readLine(

Load image into FileReader

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问题 I want to load an image from an url into filereader in order to obtain a data url of that image. I tried to search for the solution on google but i can only find solutions to read them from the file input on a local computer. 回答1: If you want a usable data-URI representation of the image, then I suggest to load the image in a <img> tag, paint it on a <canvas> then use the .toDataURL() method of the canvas. Otherwise, you need to use XMLHttpRequest to get the image blob (set the responseType

Display image from blob using javascript and websockets

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I'm currently working on a WebSocket application that is displaying images send by a C++ server. I've seen a couple of topics around there but I can't seem to get rid of this error in Firefox: Image corrupt or truncated: data:image/png;base64,[some data] Here's the Javascript code I'm using to display my blob: socket.onmessage = function(msg) { var blob = msg.data; var reader = new FileReader(); reader.onloadend = function() { var string = reader.result; var buffer = Base64.encode(string); var data = "data:image/png;base64,"+buffer; var image = document.getElementById('image'); image.src =

Difference between java.io.PrintWriter and java.io.BufferedWriter?

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Please look through code below: // A.class File file = new File("blah.txt"); FileWriter fileWriter = new FileWriter(file); PrintWriter printWriter = new PrintWriter(fileWriter); // B.class File file = new File("blah.txt"); FileWriter fileWriter = new FileWriter(file); BufferedWriter bWriter = new BufferedWriter(fileWriter); What is the difference between these two methods? When should we use PrintWriter over BufferedWriter? TofuBeer The API reference for BufferedWriter and PrintWriter detail the differences. The main reason to use the PrintWriter is to get access to the printXXX methods like

GZIPInputStream reading line by line

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I have a file in .gz format. The java class for reading this file is GZIPInputStream. However, this class doesn't extend the BufferedReader class of java. As a result, I am not able to read the file line by line. I need something like this reader = new MyGZInputStream( some constructor of GZInputStream) reader.readLine()... I though of creating my class which extends the Reader or BufferedReader class of java and use GZIPInputStream as one of its variable. import java.io.BufferedReader; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import

Are there file size limitations when using javascript FileReader API?

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问题 You can use javascript FileReader API to display a preview of an image which is provided from a file input field. This comes in very useful in the sense that you don't have to use server side php and ajax to display the image. My question though is this: Is there any limit to the size of the image file being used? Like if a user was to select an image that is 20MB, would the filereader be able to handle it? And would the machines memory potentially become max-ed out? I'm testing just locally

Javascript Promises with FileReader()

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问题 I have the following HTML Code: <input type='file' multiple> And Here's my JS Code: var inputFiles = document.getElementsByTagName("input")[0]; inputFiles.onchange = function(){ var fr = new FileReader(); for(var i = 0; i < inputFiles.files.length; i++){ fr.onload = function(){ console.log(i) // Prints "0, 3, 2, 1" in case of 4 chosen files } } fr.readAsDataURL(inputFiles.files[i]); } So my question is, how can I make this loop synchronous ? That is first wait for the file to finish loading