show canvas on image when button is clicked
< div class = "info" > < p id = "points-info" > No points yet </ p > </ div > < div class = "output" > < img id = "image" src = "https://upload.wikimedia.org/wikipedia/commons/thumb/b/b6/Image_created_with_a_mobile_phone.png/1200px-Image_created_with_a_mobile_phone.png" width = "500" height = "500" > < canvas id = "canvas" width = "500" height = "500" ></ canvas > < p id = "coordinates" ></ p > </ div > < button id = "show-canvas-btn" > Show Canvas </ button > < style > canvas { width : 500px ; height : 500px ; display : none ; border : 3px solid #333 ; background-size : cover ; cursor : crosshair ; } </ style > < script > var canvas = document . getElementById ( 'canvas' ); var ctx = canvas . getContext (