I'm using expo to build a cross-platform application. In my app, I have a screen where user can select images or videos to upload.
When I use expo-image-picker to select image it gives me an object which its uri starts with file:/// and I can use this uri to display the image.
When I use expo-image-picker-multiple to select multiple images it gives me objects and the uri starts with asset-library:// and I can't use this uri to display the content of it nor send it to server.
How can I convert this asset-library:// to file://? What keyword should I use to get better results when doing google search on this problem or which tool should I use? I can't really find a proper solution to this one. This occurs on IOS devices.
Thanks!
[EDIT]
here is my code
var assetUri = 'asset-library://....'
var tempDir = `${FileSystem.cacheDirectory}${Math.random().toString(36).substring(7)}.jpg`
FileSystem.copyAsync({
from: assetUri,
to: tempDir
})
try {
var assetResult = await FileSystem.readAsStringAsync(tempDir, {
encoding: FileSystem.EncodingType.UTF8
})
console.log(assetResult)
}
catch(e) {
console.log(e)
}
File 'file:///var/mobile/Containers/Data/Application/0E-FC42-4630-B3C7-537D5EFB7D1F/Library/Caches/ExponentExperienceData/ichardexpohong/gwmke.jpg' could not be read.
I wanted only the filename so i used
let filename= result.assets[0].uri.split('/')[result.assets[0].uri.split('/').length-1]
so maybe if the path after both asset-library and file:// are the same you can use
take away the asset-library:// then replace it with file://
let uri='file://' + object.uri.split('asset-library://')[1]
hope it helps
In a datatables column I want to display an image. The image is generated by sending the cell data to a 3rd party API that requires a POST request and returns a raw/binary png image.
What works just fine outside of datatables is:
// jquery ajax call. data is binary/raw png image
success: function ( data ) {
var image = document.getElementById(image_tag_id)
var url = window.URL || window.webkitURL;
image.src = url.createObjectURL(data);
}
This is inside a function that takes the image tags id and the data as arguments. Previously I used the tag (HTMLElement) directly but changed it to the id to play with datatables render function.
This change actually makes what I want theoretically work (came up while writing this question) with below render function:
"render": function ( data, type, row, meta ) {
if (type==="display") {
var tag_id = "image-" + meta.row;
getImage(tag_id, data);
return '<img id="' + tag_id + '">';
} else {
return data;
}
}
But this has a race condition. It assumes the returned html string always generates the tag faster than the image is fetched via ajax call (which probably always is the case but it I don't like it)
So how can I solve this issue better? Have render only create image tags and do the rest after?
Instead of getting the image in render, one can simply create a empty image tag with a class set. Then in drawCallback function, iterate over all the generated image tags and get the image via ajax call. This ensures there is no race condition.
However I went a different way and made my own service that works with GET requests. This then allows to set the src attribute of the image tags like one normally would. On top of that the images also can be cached and the source data for the image doesn't need to be transferred to the web page.
Is there a way to the current request url or path in Handlebars? I need to be able to switch what parts of the theme is loaded based on paths. I've tried {{url}} ... no luck. Using latest Stencil with Cornerstone.
I had to do something like this for a project with 3 different category page layouts. Without custom category templates in Stencil, you have to get a little creative.
First, inject the handlebars URL into your category.js file using the BigCommerce's inject handlebar helper seen here. Then parse it so you get only the unique parts, then perform some logic based on what you want to do.
I used the breadcrumb li length as an indicator of how deep I was in the category tree. There is likely a better way, but this is what I thought of first, and it worked just fine.
category.html
{{inject "currentPage" category.url}}
category.js
var pageURL = this.context.currentPage;
var pageURL = pageURL.replace(/\//g," ").replace("http:","").replace("storeurl.mybigcommerce.com","").replace("storeurl.com","").trim();
var catName = pageURL.substr(0,pageURL.indexOf(' '));
console.log('pageURL = ' + pageURL);
console.log('catName = ' + catName);
console.log($('ul.breadcrumbs li').length);
if( $('ul.breadcrumbs li').length == 3 ){
if(catName == "black-decker"){
if($(".cat-img").length){
$(".page").addClass("model-list");
$(".cat-img").hide();
$(".page").append("<div class='model-wrap'><div class='model-catalog' data-reveal-id='myModal'><span class='click-larger'>Click to view larger</span></div></div>");
$(".sidebarBlock-heading").text("Select Your Model Number Below:");
$(".brand-img").each(function(){
$(this).addClass(catName);
});
} else {
$(".page").addClass("model-list");
$(".sidebarBlock-heading").text("Select Your Model Number Below:");
$(".brand-img").each(function(){
$(this).addClass(catName);
});
// make page full width
$(".page-sidebar.cf.Left").addClass("full-width");
}
}
// MORE CODE etc...
I am having trouble with blob URLs.
I was searching for src of a video tag on YouTube and I found that the video src was like:
src="blob:https://video_url"
I opened the blob URL that was in src of the video, but it gave an error. I can't open the link, but it was working with the src tag. How is this possible?
I have a few questions:
What is a blob URL?
Why it is used?
Can I make my own blob URL on a server?
Any additional details about blob URLs would be helpful as well.
Blob URLs (ref W3C, official name) or Object-URLs (ref. MDN and method name) are used with a Blob or a File object.
src="blob:https://crap.crap" I opened the blob url that was in src of
video it gave a error and i can't open but was working with the src
tag how it is possible?
Blob URLs can only be generated internally by the browser. URL.createObjectURL() will create a special reference to the Blob or File object which later can be released using URL.revokeObjectURL(). These URLs can only be used locally in the single instance of the browser and in the same session (ie. the life of the page/document).
What is blob url?
Why it is used?
Blob URL/Object URL is a pseudo protocol to allow Blob and File objects to be used as URL source for things like images, download links for binary data and so forth.
For example, you can not hand an Image object raw byte-data as it would not know what to do with it. It requires for example images (which are binary data) to be loaded via URLs. This applies to anything that require an URL as source. Instead of uploading the binary data, then serve it back via an URL it is better to use an extra local step to be able to access the data directly without going via a server.
It is also a better alternative to Data-URI which are strings encoded as Base-64. The problem with Data-URI is that each char takes two bytes in JavaScript. On top of that a 33% is added due to the Base-64 encoding. Blobs are pure binary byte-arrays which does not have any significant overhead as Data-URI does, which makes them faster and smaller to handle.
Can i make my own blob url on a server?
No, Blob URLs/Object URLs can only be made internally in the browser. You can make Blobs and get File object via the File Reader API, although BLOB just means Binary Large OBject and is stored as byte-arrays. A client can request the data to be sent as either ArrayBuffer or as a Blob. The server should send the data as pure binary data. Databases often uses Blob to describe binary objects as well, and in essence we are talking basically about byte-arrays.
if you have then Additional detail
You need to encapsulate the binary data as a BLOB object, then use URL.createObjectURL() to generate a local URL for it:
var blob = new Blob([arrayBufferWithPNG], {type: "image/png"}),
url = URL.createObjectURL(blob),
img = new Image();
img.onload = function() {
URL.revokeObjectURL(this.src); // clean-up memory
document.body.appendChild(this); // add image to DOM
}
img.src = url; // can now "stream" the bytes
This Javascript function supports to show the difference between the Blob File API and the Data API to download a JSON file in the client browser:
/**
* Save a text as file using HTML <a> temporary element and Blob
* #author Loreto Parisi
*/
var saveAsFile = function(fileName, fileContents) {
if (typeof(Blob) != 'undefined') { // Alternative 1: using Blob
var textFileAsBlob = new Blob([fileContents], {type: 'text/plain'});
var downloadLink = document.createElement("a");
downloadLink.download = fileName;
if (window.webkitURL != null) {
downloadLink.href = window.webkitURL.createObjectURL(textFileAsBlob);
} else {
downloadLink.href = window.URL.createObjectURL(textFileAsBlob);
downloadLink.onclick = document.body.removeChild(event.target);
downloadLink.style.display = "none";
document.body.appendChild(downloadLink);
}
downloadLink.click();
} else { // Alternative 2: using Data
var pp = document.createElement('a');
pp.setAttribute('href', 'data:text/plain;charset=utf-8,' +
encodeURIComponent(fileContents));
pp.setAttribute('download', fileName);
pp.onclick = document.body.removeChild(event.target);
pp.click();
}
} // saveAsFile
/* Example */
var jsonObject = {"name": "John", "age": 30, "car": null};
saveAsFile('out.json', JSON.stringify(jsonObject, null, 2));
The function is called like saveAsFile('out.json', jsonString);. It will create a ByteStream immediately recognized by the browser that will download the generated file directly using the File API URL.createObjectURL.
In the else, it is possible to see the same result obtained via the href element plus the Data API, but this has several limitations that the Blob API has not.
I have modified working solution to handle both the case.. when video is uploaded and when image is uploaded .. hope it will help some.
HTML
<input type="file" id="fileInput">
<div> duration: <span id='sp'></span><div>
Javascript
var fileEl = document.querySelector("input");
fileEl.onchange = function(e) {
var file = e.target.files[0]; // selected file
if (!file) {
console.log("nothing here");
return;
}
console.log(file);
console.log('file.size-' + file.size);
console.log('file.type-' + file.type);
console.log('file.acutalName-' + file.name);
let start = performance.now();
var mime = file.type, // store mime for later
rd = new FileReader(); // create a FileReader
if (/video/.test(mime)) {
rd.onload = function(e) { // when file has read:
var blob = new Blob([e.target.result], {
type: mime
}), // create a blob of buffer
url = (URL || webkitURL).createObjectURL(blob), // create o-URL of blob
video = document.createElement("video"); // create video element
//console.log(blob);
video.preload = "metadata"; // preload setting
video.addEventListener("loadedmetadata", function() { // when enough data loads
console.log('video.duration-' + video.duration);
console.log('video.videoHeight-' + video.videoHeight);
console.log('video.videoWidth-' + video.videoWidth);
//document.querySelector("div")
// .innerHTML = "Duration: " + video.duration + "s" + " <br>Height: " + video.videoHeight; // show duration
(URL || webkitURL).revokeObjectURL(url); // clean up
console.log(start - performance.now());
// ... continue from here ...
});
video.src = url; // start video load
};
} else if (/image/.test(mime)) {
rd.onload = function(e) {
var blob = new Blob([e.target.result], {
type: mime
}),
url = URL.createObjectURL(blob),
img = new Image();
img.onload = function() {
console.log('iamge');
console.dir('this.height-' + this.height);
console.dir('this.width-' + this.width);
URL.revokeObjectURL(this.src); // clean-up memory
console.log(start - performance.now()); // add image to DOM
}
img.src = url;
};
}
var chunk = file.slice(0, 1024 * 1024 * 10); // .5MB
rd.readAsArrayBuffer(chunk); // read file object
};
jsFiddle Url
https://jsfiddle.net/PratapDessai/0sp3b159/
The OP asks:
What is blob URL? Why is it used?
Blob is just byte sequence. Browsers recognize Blobs as byte streams. It is used to get byte stream from source.
According to Mozilla's documentation
A Blob object represents a file-like object of immutable, raw data. Blobs represent data that isn't necessarily in a JavaScript-native format. The File interface is based on Blob, inheriting blob functionality and expanding it to support files on the user's system.
The OP asks:
Can i make my own blob url on a server?
Yes you can there are several ways to do so for example try http://php.net/manual/en/function.ibase-blob-echo.php
Read more here:
https://developer.mozilla.org/en-US/docs/Web/API/Blob
http://www.w3.org/TR/FileAPI/#dfn-Blob
https://url.spec.whatwg.org/#urls
blob urls are used for showing files that the user uploaded, but they are many other purposes, like that it could be used for secure file showing, like how it is a little difficult to get a YouTube video as a video file without downloading an extension. But, they are probably more answers. My research is mostly just me using Inspect to try to get a YouTube video and an online article.
Another use case of blob urls is to load resources from the server, apply hacks and then tell the browser to interpret them.
One such example would be to load template files or even scss files.
Here is the scss example:
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/sass.js/0.11.1/sass.sync.min.js"></script>
function loadCSS(text) {
const head = document.getElementsByTagName('head')[0]
const style = document.createElement('link')
const css = new Blob([text], {type: 'text/css'})
style.href = window.URL.createObjectURL(css)
style.type = 'text/css'
style.rel = 'stylesheet'
head.append(style)
}
fetch('/style.scss').then(res => res.text()).then(sass => {
Sass.compile(sass, ({text}) => loadCSS(text))
})
Now you could swap out Sass.compile for any kind of transformation function you like.
Blob urls keeps your DOM structure clean this way.
I'm sure by now you have your answers, so this is just one more thing you can do with it.
In Rally we have a custom App which displays a table. Is there a way to export this table to Excel?
Rally Add-in for Excel looks good, but it only works for Office 2010 and we are stuck on 2007. But I did find this solution that's simple and it works in Firefox. Added a button to the app, when clicked I pass in the div_id of the table along with a Title.
var tableToExcel = (function() {
var uri = 'data:application/vnd.ms-excel;base64,'
, template = '<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:x="urn:schemas-microsoft-com:office:excel" xmlns="http://www.w3.org/TR/REC-html40"><head><!--[if gte mso 9]><xml><x:ExcelWorkbook><x:ExcelWorksheets><x:ExcelWorksheet><x:Name>{worksheet}</x:Name><x:WorksheetOptions><x:DisplayGridlines/></x:WorksheetOptions></x:ExcelWorksheet></x:ExcelWorksheets></x:ExcelWorkbook></xml><![endif]--></head><body><table>{table}</table></body></html>'
, base64 = function(s) { return window.btoa(unescape(encodeURIComponent(s))) }
, format = function(s, c) { return s.replace(/{(\w+)}/g, function(m, p) { return c[p]; }) }
return function(table, name) {
if (!table.nodeType) table = document.getElementById(table)
var ctx = {worksheet: name || 'Worksheet', table: table.innerHTML}
window.location.href = uri + base64(format(template, ctx))
}
})();
var onClicked = function(sender, eventArgs) {
var buttonValue = eventArgs.value;
tableToExcel('mashup_table', 'Reviews Report Table');
};
Currently there is no way to export data from a table in an App.
Have you seen the Rally Add-in for Excel?
Michael,
You can try and use the data URI scheme to make your export work. It is possible to get the data from a AppSdk table and creating a comma delimited string. You could then make one of the special URIs to download the contents as a .csv and open them in excel.
We have been kicking around the idea of making the SDK be able to export it's data to from their components but the lack of constant support for data URIs has been a blocking point.
I don't know what browsers you have to support internally but that may be a nice start for a client side solution.
Here is a solution that works with ExtJs that you may find useful.