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HTML Template
<html>
<form>
Image to resize: <input type="file" id="getImage"><br><br>
</form>
<img src="." id="image">
<html>
Java Script
<script>
document.getElementById('getImage').onchange = imageResize(60,60);
var imageResize = function (Width, Height) {
//-- GET FILE FROM FORM
var selectedFile = this.files[0];
//-- GET BASE 64
File.prototype.convertToBase64 = function (callback) {
var reader = new FileReader();
reader.onload = function (e) {
callback(e.target.result);
};
reader.readAsDataURL(this);
};
selectedFile.convertToBase64(function (base64) {
//-- MAKE IMAGE
var img = document.createElement('img');
img.src = base64;
//-- PUSH INTO CANVAS
img.onload = function () {
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
canvas.width = Width; // If i change Width & Height to numbers it works!!
canvas.height = Height;
ctx.drawImage(this, 0, 0, Width, Height);
//-- SHOW IMAGE ON PAGE
document.getElementById("image").src = canvas.toDataURL();
};
});
};
</script>
Just above I'm setting the canvas width and height to 60x60 but i cant use the variables I've passed in without getting an error, and I cant figure out why. the error is
Uncaught TypeError: Cannot read property 'files' of undefined
416
here you should attach the event listener to input element.but instead you attached to img element
and you also want to access the files inside the event listener,so you should pass this reference to the listener
and the way you are attaching the event is not right.
your are doing this document.getElementById('getImage').onchange = imageResize(60,60);
this is wrong as it will execute the imageResize() and assigns the result to on change event.
actually you should attach reference of the function like below
document.getElementById('getImage').onchange = imageResize;
i edited your code a little. try this snippet.
var imageResize = function(Width, Height, files) {
var selectedFile = files[0];
File.prototype.convertToBase64 = function(callback) {
var reader = new FileReader();
reader.onload = function(e) {
callback(e.target.result);
};
reader.readAsDataURL(this);
};
selectedFile.convertToBase64(function(base64) {
var img = document.createElement('img');
img.src = base64;
img.onload = function() {
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
canvas.width = Width;
canvas.height = Height;
ctx.drawImage(this, 0, 0, Width, Height);
document.getElementById("image").src = canvas.toDataURL();
};
});
};
var file = document.getElementById('getImage');
file.onchange = function() {
imageResize(160, 160, this.files);
};<form>
Image to resize:
<input type="file" id="getImage">
<br>
<br>
</form>
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