Develop Reference

Uploading an image from computer to Fabric.JS Canvas

Are there any Fabric.JS Wizards out there?
I've done my fair research and I can't seem to find much of an explanation on how to add an image to the fabric.JS canvas.
User Journey:
a) User uploads an image from an input file type button.
b) As soon as they have selected an image from their computer I want to place it into the users canvas.
So far I've got to storing the image into an expression, this is my code below:
scope.setFile = function(element) {
scope.currentFile = element.files[0];
var reader = new FileReader();
/**
*
*/
reader.onload = function(event) {
// This stores the image to scope
scope.imageSource = event.target.result;
scope.$apply();
};
// when the file is read it triggers the onload event above.
reader.readAsDataURL(element.files[0]);
};
My HTML/Angular:
<label class="app-file-input button">
<i class="icon-enter"></i>
<input type="file"
id="trigger"
onchange="angular.element(this).scope().setFile(this)"
accept="image/*">
</label>
If you haven't guessed yet I am using a MEAN stack. Mongoose, Express, Angular and Node.
The scope imageSource is what the image is store in. I've read this SO
and it talks about pushing the image to the Image object with my result, and then pass it to the fabric.Image object. Has anyone done a similar thing that they can help me with?
Thanks in advance
**** UPDATE ****
Directive defines the canvas variable:
var canvas = new fabric.Canvas(attrs.id, {
isDrawingMode: true
});

Upload image from computer with Fabric js.
var canvas = new fabric.Canvas('canvas');
document.getElementById('file').addEventListener("change", function (e) {
var file = e.target.files[0];
var reader = new FileReader();
reader.onload = function (f) {
var data = f.target.result;
fabric.Image.fromURL(data, function (img) {
var oImg = img.set({left: 0, top: 0, angle: 00,width:100, height:100}).scale(0.9);
canvas.add(oImg).renderAll();
var a = canvas.setActiveObject(oImg);
var dataURL = canvas.toDataURL({format: 'png', quality: 0.8});
});
};
reader.readAsDataURL(file);
});
canvas{
border: 1px solid black;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://rawgit.com/kangax/fabric.js/master/dist/fabric.min.js"></script>
<input type="file" id="file"><br />
<canvas id="canvas" width="450" height="450"></canvas>

once you have a dataURL done, you can do either:
reader.onload = function(event) {
// This stores the image to scope
fabric.Image.fromURL(event.target.result, function(img) {
canvas.add(img);
});
scope.$apply();
};
Or you put on your image tag an onload event where you do:
var img = new fabric.Image(your_img_element);
canvas.add(img);

This is for drag and drop from desktop using the dataTransfer interface.
canvas.on('drop', function(event) {
// prevent the file to open in new tab
event.e.stopPropagation();
event.e.stopImmediatePropagation();
event.e.preventDefault();
// Use DataTransfer interface to access the file(s)
if(event.e.dataTransfer.files.length > 0){
var files = event.e.dataTransfer.files;
for (var i = 0, f; f = files[i]; i++) {
// Only process image files.
if (f.type.match('image.*')) {
// Read the File objects in this FileList.
var reader = new FileReader();
// listener for the onload event
reader.onload = function(evt) {
// put image on canvas
fabric.Image.fromURL(evt.target.result, function(obj) {
obj.scaleToHeight(canvas.height);
obj.set('strokeWidth',0);
canvas.add(obj);
});
};
// Read in the image file as a data URL.
reader.readAsDataURL(f);
}
}
}
});
Resources
https://developer.mozilla.org/en-US/docs/Web/API/HTML_Drag_and_Drop_API/File_drag_and_drop

Is there a way to control the size of an image when using html output tag?

I'm using the following code to upload an image for viewing before passing it on to my server. I want to put constraints on the size of the image using css. The CSS is having no effect on the image as it is rendered by output. Is there a way around this? I tried adding the CSS attribute to its surrounding div but that did not work either.
The HTML:
<input type="file" id="files" name="files[]" file-model="myFile"/>
<output id="list" class="resize-image" alt="Image"></output>
The CSS:
#list{
max-width: 15px;
max-height: 7px;
}
The Javascript:
var handleFileSelect = function (evt) {//already set up for multiple files; not what i want to do.
var files = evt.target.files; // FileList object
// Loop through the FileList and render image files as thumbnails.
for (var i = 0, f; f = files[i]; i++) {
// Only process image files.
if (!f.type.match('image.*')) {
continue;
}
var reader = new FileReader();
// Closure to capture the file information.
reader.onload = (function(theFile) {
return function(e) {
// Render thumbnail.
var span = document.createElement('span');
span.innerHTML = ['<img class="thumb" src="', e.target.result,
'" title="', escape(theFile.name), '"/>'].join('');
document.getElementById('list').insertBefore(span, null);
};
})(f);
// Read in the image file as a data URL.
reader.readAsDataURL(f);
}
}
document.getElementById('files').addEventListener('change', handleFileSelect, false);

The simples would be to use height and width img tag attributes.
var span = document.createElement('span');
span.innerHTML = ['<img height="7" width="15" class="thumb" src="', e.target.result,
'" title="', escape(theFile.name), '"/>'].join('');
document.getElementById('list').insertBefore(span, null);
If you really would like to use .css for this task you can use background-size, but then background property must be set with url to the image in css.
You can also simply override the img tag in css like this:
img{
max-width: 100px;
max-height: 100px;
}
Here you can test both approaches : http://www.w3schools.com/cssref/tryit.asp?filename=trycss3_background-size

Drag and drop and scale images but user's upload pic isn't draggable and resizable

Hello guys i found this amazing drag and drop and resize image and i am trying to add a custom modification. I added an upload button so user can upload a photo.
i added the function bellow to find the last img id, create a new one and replace the latest id and img source. The user's photo uploading well but it's not draggable and resizable like other objects.
Official projects link is: http://tympanus.net/Tutorials/ImageVampUp/
The code that i added is:
<script>
$(document).ready(function() {
$("input").change(function(e) {
for (var i = 0; i < e.originalEvent.srcElement.files.length; i++) {
var file = e.originalEvent.srcElement.files[i];
var reader = new FileReader();
reader.onloadend = function() {
var newoid = parseInt($("#objects .obj_item:last img").attr("ID").split("_")[1], 10) + 1;
var newoimage = reader.result;
$("#objects").append("<div class='obj_item' style='width:80px; height:80px; float:left; margin-left:5px; margin-top:5px;'><img id='"+newoid+"' width='80' height='80' class='ui-widget-content' src='"+newoimage+"' alt='el'/></div>");
//$('#obj_25').attr('src', reader.result);
}
reader.readAsDataURL(file);
}
});
});
</script>
and inside projects left bar i added a div with an input so user can load the pic:
<input type='file' onchange="readURL(this);" />

Just invoke the following putting it in a function after the image is appended:
$('#objects img:last').resizable({
/* only diagonal (south east) */
handles : 'se',
stop : resizestop
}).parent('.ui-wrapper').draggable({
revert : 'invalid'
});

View image before upload

I need to show upload image before upload using jquery but in chrome path shown fake path like this:
C:\fakepath\myImage.jpg
and in firefox it's shown only file name:
myImage.jpg
so how can me preview my image file before uploading
<input type="file">
<img src="" class="preview" />
if that is impossible.. what about HTML5?

I don't know of a jQuery function (sorry), but it is possible with HTML5, and most browsers support this HTML5 function. I found a piece of code in HTML5rocks (1):
<style>
.thumb {
height: 75px;
border: 1px solid #000;
margin: 10px 5px 0 0;
}
</style>
<input type="file" id="files" name="files[]" multiple />
<output id="list"></output>
<script>
function handleFileSelect(evt) {
var files = evt.target.files; // FileList object
// Loop through the FileList and render image files as thumbnails.
for (var i = 0, f; f = files[i]; i++) {
// Only process image files.
if (!f.type.match('image.*')) {
continue;
}
var reader = new FileReader();
// Closure to capture the file information.
reader.onload = (function(theFile) {
return function(e) {
// Render thumbnail.
var span = document.createElement('span');
span.innerHTML = ['<img class="thumb" src="', e.target.result,
'" title="', escape(theFile.name), '"/>'].join('');
document.getElementById('list').insertBefore(span, null);
};
})(f);
// Read in the image file as a data URL.
reader.readAsDataURL(f);
}
}
document.getElementById('files').addEventListener('change', handleFileSelect, false);
</script>
Good luck :)
(1) HTML5rocks - Reading Files: http://www.html5rocks.com/en/tutorials/file/dndfiles/

You can't. You need to upload image using ajax, for example, return image url and finally display it.

HTML5, JavaScript: Drag and Drop File from External Window (Windows Explorer)

Can I kindly ask for a good working example of HTML5 File Drag and Drop implementation? The source code should work if drag and drop is performed from external application(Windows Explorer) to browser window. It should work on as many browsers as possible.
I would like to ask for a sample code with good explanation. I do not wish to use third party libraries, as I will need to modify the code according to my needs. The code should be based on HTML5 and JavaScript. I do not wish to use JQuery.
I spent the whole day searching for good source of material, but surprisingly, I did not find anything good. The examples I found worked for Mozilla but did not work for Chrome.

Here is a dead-simple example. It shows a red square. If you drag an image over the red square it appends it to the body. I've confirmed it works in IE11, Chrome 38, and Firefox 32. See the Html5Rocks article for a more detailed explanation.
var dropZone = document.getElementById('dropZone');
// Optional. Show the copy icon when dragging over. Seems to only work for chrome.
dropZone.addEventListener('dragover', function(e) {
e.stopPropagation();
e.preventDefault();
e.dataTransfer.dropEffect = 'copy';
});
// Get file data on drop
dropZone.addEventListener('drop', function(e) {
e.stopPropagation();
e.preventDefault();
var files = e.dataTransfer.files; // Array of all files
for (var i=0, file; file=files[i]; i++) {
if (file.type.match(/image.*/)) {
var reader = new FileReader();
reader.onload = function(e2) {
// finished reading file data.
var img = document.createElement('img');
img.src= e2.target.result;
document.body.appendChild(img);
}
reader.readAsDataURL(file); // start reading the file data.
}
}
});
<div id="dropZone" style="width: 100px; height: 100px; background-color: red"></div>

The accepted answer provides an excellent link for this topic; however, per SO rules, pure link answers should be avoided since the links can rot at any time. For this reason, I have taken the time to summarize the content of the link for future readers.
Getting Started
Prior to implementing a method to upload files to your website, you should ensure that the browsers you choose to support will be capable of fully supporting the File API. You can test this quickly with the snippet of Javascript below:
// Check for the various File API support.
if (window.File && window.FileReader && window.FileList && window.Blob) {
// Great success! All the File APIs are supported.
} else {
alert('The File APIs are not fully supported in this browser.');
}
You can modify the snippet above to meet your needs of course.
Form Input
The most common way to upload a file is to use the standard <input type="file"> element. JavaScript returns the list of selected File objects as a FileList.
function handleFileSelect(evt) {
var files = evt.target.files; // FileList object
// files is a FileList of File objects. List some properties.
var output = [];
for (var i = 0, f; f = files[i]; i++) {
output.push('<li><strong>', escape(f.name), '</strong> (', f.type || 'n/a', ') - ',
f.size, ' bytes, last modified: ',
f.lastModifiedDate ? f.lastModifiedDate.toLocaleDateString() : 'n/a',
'</li>');
}
document.getElementById('list').innerHTML = '<ul>' + output.join('') + '</ul>';
}
document.getElementById('files').addEventListener('change', handleFileSelect, false);
<input type="file" id="files" name="files[]" multiple />
<output id="list"></output>
Drag and Drop
Making simple modifications to the snippet above allows us to provide drag and drop support.
function handleFileSelect(evt) {
evt.stopPropagation();
evt.preventDefault();
var files = evt.dataTransfer.files; // FileList object.
// files is a FileList of File objects. List some properties.
var output = [];
for (var i = 0, f; f = files[i]; i++) {
output.push('<li><strong>', escape(f.name), '</strong> (', f.type || 'n/a', ') - ',
f.size, ' bytes, last modified: ',
f.lastModifiedDate ? f.lastModifiedDate.toLocaleDateString() : 'n/a',
'</li>');
}
document.getElementById('list').innerHTML = '<ul>' + output.join('') + '</ul>';
}
function handleDragOver(evt) {
evt.stopPropagation();
evt.preventDefault();
evt.dataTransfer.dropEffect = 'copy'; // Explicitly show this is a copy.
}
// Setup the dnd listeners.
var dropZone = document.getElementById('drop_zone');
dropZone.addEventListener('dragover', handleDragOver, false);
dropZone.addEventListener('drop', handleFileSelect, false);
#drop_zone {
min-height: 10em;
background: #eee;
}
<div id="drop_zone">Drop files here</div>
<output id="list"></output>
Reading Files
Now you've obtained a reference to the File, you can instantiate a FileReader to read its contents into memory. When the load completes the onload event is fired and its result attribute can be used to access the file data. Feel free to look at the references for FileReader to cover the four available options for reading a file.
The example below filters out images from the user's selection, calls reader.readAsDataURL() on the file, and renders a thumbnail by setting the src attribute to a data URL.
function handleFileSelect(evt) {
var files = evt.target.files; // FileList object
// Loop through the FileList and render image files as thumbnails.
for (var i = 0, f; f = files[i]; i++) {
// Only process image files.
if (!f.type.match('image.*')) {
continue;
}
var reader = new FileReader();
// Closure to capture the file information.
reader.onload = (function(theFile) {
return function(e) {
// Render thumbnail.
var span = document.createElement('span');
span.innerHTML = ['<img class="thumb" src="', e.target.result,
'" title="', escape(theFile.name), '"/>'].join('');
document.getElementById('list').insertBefore(span, null);
};
})(f);
// Read in the image file as a data URL.
reader.readAsDataURL(f);
}
}
document.getElementById('files').addEventListener('change', handleFileSelect, false);
.thumb {
height: 75px;
border: 1px solid #000;
margin: 10px 5px 0 0;
}
<input type="file" id="files" name="files[]" multiple />
<output id="list"></output>
Slicing
In some cases reading the entire file into memory isn't the best option. For example, say you wanted to write an async file uploader. One possible way to speed up the upload would be to read and send the file in separate byte range chunks. The server component would then be responsible for reconstructing the file content in the correct order.
The following example demonstrates reading chunks of a file. Something worth noting is that it uses the onloadend and checks the evt.target.readyState instead of using the onload event.
function readBlob(opt_startByte, opt_stopByte) {
var files = document.getElementById('files').files;
if (!files.length) {
alert('Please select a file!');
return;
}
var file = files[0];
var start = parseInt(opt_startByte) || 0;
var stop = parseInt(opt_stopByte) || file.size - 1;
var reader = new FileReader();
// If we use onloadend, we need to check the readyState.
reader.onloadend = function(evt) {
if (evt.target.readyState == FileReader.DONE) { // DONE == 2
document.getElementById('byte_content').textContent = evt.target.result;
document.getElementById('byte_range').textContent =
['Read bytes: ', start + 1, ' - ', stop + 1,
' of ', file.size, ' byte file'].join('');
}
};
var blob = file.slice(start, stop + 1);
reader.readAsBinaryString(blob);
}
document.querySelector('.readBytesButtons').addEventListener('click', function(evt) {
if (evt.target.tagName.toLowerCase() == 'button') {
var startByte = evt.target.getAttribute('data-startbyte');
var endByte = evt.target.getAttribute('data-endbyte');
readBlob(startByte, endByte);
}
}, false);
#byte_content {
margin: 5px 0;
max-height: 100px;
overflow-y: auto;
overflow-x: hidden;
}
#byte_range { margin-top: 5px; }
<input type="file" id="files" name="file" /> Read bytes:
<span class="readBytesButtons">
<button data-startbyte="0" data-endbyte="4">1-5</button>
<button data-startbyte="5" data-endbyte="14">6-15</button>
<button data-startbyte="6" data-endbyte="7">7-8</button>
<button>entire file</button>
</span>
<div id="byte_range"></div>
<div id="byte_content"></div>
Monitoring Progress
One of the nice things that we get for free when using async event handling is the ability to monitor the progress of the file read; useful for large files, catching errors, and figuring out when a read is complete.
The onloadstart and onprogress events can be used to monitor the progress of a read.
The example below demonstrates displaying a progress bar to monitor the status of a read. To see the progress indicator in action, try a large file or one from a remote drive.
var reader;
var progress = document.querySelector('.percent');
function abortRead() {
reader.abort();
}
function errorHandler(evt) {
switch(evt.target.error.code) {
case evt.target.error.NOT_FOUND_ERR:
alert('File Not Found!');
break;
case evt.target.error.NOT_READABLE_ERR:
alert('File is not readable');
break;
case evt.target.error.ABORT_ERR:
break; // noop
default:
alert('An error occurred reading this file.');
};
}
function updateProgress(evt) {
// evt is an ProgressEvent.
if (evt.lengthComputable) {
var percentLoaded = Math.round((evt.loaded / evt.total) * 100);
// Increase the progress bar length.
if (percentLoaded < 100) {
progress.style.width = percentLoaded + '%';
progress.textContent = percentLoaded + '%';
}
}
}
function handleFileSelect(evt) {
// Reset progress indicator on new file selection.
progress.style.width = '0%';
progress.textContent = '0%';
reader = new FileReader();
reader.onerror = errorHandler;
reader.onprogress = updateProgress;
reader.onabort = function(e) {
alert('File read cancelled');
};
reader.onloadstart = function(e) {
document.getElementById('progress_bar').className = 'loading';
};
reader.onload = function(e) {
// Ensure that the progress bar displays 100% at the end.
progress.style.width = '100%';
progress.textContent = '100%';
setTimeout("document.getElementById('progress_bar').className='';", 2000);
}
// Read in the image file as a binary string.
reader.readAsBinaryString(evt.target.files[0]);
}
document.getElementById('files').addEventListener('change', handleFileSelect, false);
#progress_bar {
margin: 10px 0;
padding: 3px;
border: 1px solid #000;
font-size: 14px;
clear: both;
opacity: 0;
-moz-transition: opacity 1s linear;
-o-transition: opacity 1s linear;
-webkit-transition: opacity 1s linear;
}
#progress_bar.loading {
opacity: 1.0;
}
#progress_bar .percent {
background-color: #99ccff;
height: auto;
width: 0;
}
<input type="file" id="files" name="file" />
<button onclick="abortRead();">Cancel read</button>
<div id="progress_bar"><div class="percent">0%</div></div>

Look into ondragover event. You could simply have a inside of a div that is hidden until the ondragover event fires a function that will show the div with the in it, thus letting the user drag and drop the file. Having an onchange declaration on the would let you automatically call a function (such as upload) when a file is added to the input. Make sure that the input allows for multiple files, as you have no control over how many they are going to try and drag into the browser.

This technique works very well, but if you want a binary blob rather than just to put the dragged image in an html img element, you'll need to use the 'fetch' function twice.