Resize Image Using Canvas Javascript. Event handler to resize the canvas when the document view is changed window addeventlistener resize resizecanvas false. Get viewport size getviewportsize function.
Function var canvas document getelementbyid canvas context canvas getcontext 2d. Canvassize height viewportsize height 10. Var oldcanvas canvas todataurl image png.
Canvassize width viewportsize width 10 y.
Ctx drawimage image 0 0 image width image height. Function get the precentage of height and width of the cavas based on the height and width of the window getpercentageofwindow function var viewportsize getviewportsize. The getcontext method returns an object with the properties and methods required for drawing graphics on the canvas. Now draw the image on the canvas by specifying the position width and height of the image.