So, I have a user input which serve to upload pictures. This is a simple example:
function handleImage(e){
var reader = new FileReader();
reader.onload = function(event){
var img = new Image();
img.onload = function(){
console.log (img);
}
img.src = event.target.result;
}
reader.readAsDataURL(e.target.files[0]);
}
<input type="file" onchange="handleImage(event)"><br>
As you can see, I display an Image ()
on the console
. I want to convert this Image
into a jpg file.
I understood how to get the pixels of the picture but it's completely crazy to send it to a server: It's to large!
I also tried to access to the jpg file stored in the computer but I do not achieve to anything.
The only way I found is to send it with a form
like this:
<form action="anything.php" method="post" enctype="multipart/form-data">
<input type="file" name="fileToUpload" id="fileToUpload">
</form>
And in PHP:
$_FILES["fileToUpload"]["tmp_name"]
Why not with JS?
My final goal is to send the jpg file with AJAX.
Tell me if you have some questions.
The simplest way is to use a canvas element and then invoke a download action allowing the user to select where to save the image.
You mention that the image is large, but not how much - be aware that with canvas you will also run into restrictions when the image source starts to touch around the 8k area in pixel size.
A simplified example (IE will require a polyfill for
toBlob()
).:URL.createObjectURL()
toBlob()
(more efficient on memory and performance and require no transcoding to/from Base64) to obtain aBlob
.Blob
toFile
(a subset object and it will reference the same memory) so we can also give a filename as well as (important!) a binary mime-type.Since the mime-type for the final step is binary the browser will invoke a Save as dialog.
Update: If you just are after a string (base-64 encoded) version of the newly created JPEG simply use
toDataURL()
instead oftoBlob()
: