How to specify default image URL about minipaint HOT 6 CLOSED

// Get image from url
function getDataUri(url, callback) {
    var image = new Image();
    image.onload = function () {
        var canvas = document.createElement('canvas');
        canvas.width = this.naturalWidth;
        canvas.height = this.naturalHeight;
        canvas.getContext('2d').drawImage(this, 0, 0);
        var dataUri = canvas.toDataURL('image/png');
        // Get raw image data
        callback(createJsonData(dataUri,canvas.width,canvas.height));
    };
    image.src = url;
}
function createJsonData(dataUri,width,height){
		var export_data = {};
		//get date
		var today = new Date();
		var yyyy = today.getFullYear();
		var mm = today.getMonth()+1; //January is 0!
		var dd = today.getDate();
		if(dd < 10)
			dd = '0'+dd;
		if(mm < 10)
			mm = '0'+mm;
		var today = yyyy+'-'+mm+'-'+dd;
		//basic info
		export_data.info = {
			width: width,
			height: height,
			about: 'Image data.',
			date: today,
		};
		//layers
		export_data.layers = [];
		var layer = {
			name:"Your file name",
			title:"Your file name", 
			visible: 1,
			opacity: 0,
		};
		export_data.layers.push(layer);
		//image data
		export_data.image_data = [];
		export_data.image_data.push({name: "Your name", data: dataUri});
		var data_json = JSON.stringify(export_data, null, 6);
		delete export_data;
		return data_json;
}
// Load image from url to canvas
var imgUrl = "<?php echo $imgUrl; ?>"; // url from post or like img/colorwheel.png
if(imgUrl){
	getDataUri(imgUrl, function(jsonData) {
		FILE.load_json(jsonData);
	});
}

<img alt="" id="my_image" src="img/colorwheel.png" alt="" onclick="open_image('my_image');"  />

<script>
function open_image(image_id){
	var img = document.getElementById(image_id);
	//set name
	var name = img.src.replace(/^.*[\\\/]/, '');
	LAYER.layer_add(name);
	LAYER.layer_remove(1);
	//draw canvas
	canvas_active().drawImage(img, 0, 0);
}
</script>