How do I resize the canvas content and get the resized (and compressed) image base64 data?












1















I am playing with the canvas and have created a drawing demo.



Now I can draw stuff on that canvas and get the data with .toDataURL().



Everything goes perfect except for the data of the image is too big. And I just only need a very small version of the drawing.



Is there any way (even possible) that I can resize the canvas to a smaller version and load the resized image data? It's kinda like to compress the image with pure JavaScript.



For instance, I let the user to draw on a 1000px * 500px canvas and resize it to 50px * 25px. The resized base64 data would be very small and convenient for further network-transfer. That's what I want to have.






javascript canvas







share|improve this question



























    1















    I am playing with the canvas and have created a drawing demo.



    Now I can draw stuff on that canvas and get the data with .toDataURL().



    Everything goes perfect except for the data of the image is too big. And I just only need a very small version of the drawing.



    Is there any way (even possible) that I can resize the canvas to a smaller version and load the resized image data? It's kinda like to compress the image with pure JavaScript.



    For instance, I let the user to draw on a 1000px * 500px canvas and resize it to 50px * 25px. The resized base64 data would be very small and convenient for further network-transfer. That's what I want to have.






    javascript canvas







    share|improve this question

























      1












      1








      1








      I am playing with the canvas and have created a drawing demo.



      Now I can draw stuff on that canvas and get the data with .toDataURL().



      Everything goes perfect except for the data of the image is too big. And I just only need a very small version of the drawing.



      Is there any way (even possible) that I can resize the canvas to a smaller version and load the resized image data? It's kinda like to compress the image with pure JavaScript.



      For instance, I let the user to draw on a 1000px * 500px canvas and resize it to 50px * 25px. The resized base64 data would be very small and convenient for further network-transfer. That's what I want to have.






      javascript canvas







      share|improve this question














      I am playing with the canvas and have created a drawing demo.



      Now I can draw stuff on that canvas and get the data with .toDataURL().



      Everything goes perfect except for the data of the image is too big. And I just only need a very small version of the drawing.



      Is there any way (even possible) that I can resize the canvas to a smaller version and load the resized image data? It's kinda like to compress the image with pure JavaScript.



      For instance, I let the user to draw on a 1000px * 500px canvas and resize it to 50px * 25px. The resized base64 data would be very small and convenient for further network-transfer. That's what I want to have.






      javascript canvas




      javascript canvas






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Nov 14 '18 at 8:33









      AGamePlayerAGamePlayer

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          You let your user draw on the big canvas, then you draw the big canvas as an image on the small canvas. Finally you get the small canvas image as a data URI.



          The small canvas doesn't have to be attached to the DOM.



          let bigCanvas_img = document.querySelector("bigCanvas");
          
smallCanvas_ctx.drawImage(bigCanvas_img,0,0,smallCanvas_w,smallCanvas_h);
          

          

          
let url = smallCanvas.toDataURL();





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            You let your user draw on the big canvas, then you draw the big canvas as an image on the small canvas. Finally you get the small canvas image as a data URI.



            The small canvas doesn't have to be attached to the DOM.



            let bigCanvas_img = document.querySelector("bigCanvas");
            
smallCanvas_ctx.drawImage(bigCanvas_img,0,0,smallCanvas_w,smallCanvas_h);
            

            

            
let url = smallCanvas.toDataURL();





            share|improve this answer




























              0














              You let your user draw on the big canvas, then you draw the big canvas as an image on the small canvas. Finally you get the small canvas image as a data URI.



              The small canvas doesn't have to be attached to the DOM.



              let bigCanvas_img = document.querySelector("bigCanvas");
              
smallCanvas_ctx.drawImage(bigCanvas_img,0,0,smallCanvas_w,smallCanvas_h);
              

              

              
let url = smallCanvas.toDataURL();





              share|improve this answer


























                0












                0








                0







                You let your user draw on the big canvas, then you draw the big canvas as an image on the small canvas. Finally you get the small canvas image as a data URI.



                The small canvas doesn't have to be attached to the DOM.



                let bigCanvas_img = document.querySelector("bigCanvas");
                
smallCanvas_ctx.drawImage(bigCanvas_img,0,0,smallCanvas_w,smallCanvas_h);
                

                

                
let url = smallCanvas.toDataURL();





                share|improve this answer













                You let your user draw on the big canvas, then you draw the big canvas as an image on the small canvas. Finally you get the small canvas image as a data URI.



                The small canvas doesn't have to be attached to the DOM.



                let bigCanvas_img = document.querySelector("bigCanvas");
                
smallCanvas_ctx.drawImage(bigCanvas_img,0,0,smallCanvas_w,smallCanvas_h);
                

                

                
let url = smallCanvas.toDataURL();






                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Nov 14 '18 at 8:45









                enxanetaenxaneta

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