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Var dataURL = canvas.toDataURL("image/jpeg", 1.0) Var canvas = document.createElement('canvas') Ĭanvas.getContext('2d').drawImage(image, 0, 0, w, h) Here, we can see the first part of this function: function fileChange(e) With each change of the field (that is whenever the user is selecting a new image), the function fileChange() should be called. With this line, we are assigning an event listener to our site input field. document.getElementById('inp_file').addEventListener('change', fileChange, false) However, you will find the full HTML page together with the entire code at the end of this tutorial. I want to describe our JavaScript in multiple parts. We will do this reduction with means of JavaScript later and we are storing the result of the reduction in the hidden field "img" of our form with which the image then can be submitted. Finally we do not want to send the entire large selected file to the server but only a reduction thereof. It is important that the input field is intentionally not located within the form. Fundamentally, we only need an input field for selecting the file and a form for submitting the data at this point. This tutorial is based on these other tutorials, but this not necessary to know them for understanding this one. In this tutorial, we assume that the user is selecting the image in a file dialog - in the tutorials HTML5 Canvas Upload with Ajax and HTML5 Canvas Upload with an HTML Form, I have described how to send an already existing canvas as an image to the server in order to save it there. We are using HTML 5 technologies for the minimizing such as FileReader and Canvas. However, the special thing about the size reduction is that the resizing is taking place directly and without additional software in the browser of the user on the client-side instead of by means of some server-side PHP script so that the server resources are spared. In this tutorial I would like to show you how to implement an image upload script in which the image is resized or minimized automatically.