Javascript crop and scale image to be 300 pixel-CodePudding

I want to know how we can scale and crop an image in Javascript. I want to scale it down to 300x300px and crop it a little. Do you have any suggestions ? I have the following code :

function cropImage(imagePath, newX, newY, newWidth, newHeight) {
//create an image object from the path
var img = document.createElement('img');
img.src = "data:image/png;base64," imagePath;
    
//alert(img.width);
//alert(img.height);
//initialize the canvas object
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');



    //set the canvas size to the new width and height
    canvas.width = 300;
    canvas.height = 300;
     
    //draw the image
    
        ctx.drawImage(img, newX, 75, 300, 300, 0, 0, 300, 300);
    variables.imageCrop = canvas.toDataURL();}

Thank you !

CodePudding user response：

Try it:

And learn more about .drawImage()

function cropImage(imagePath, leftRight, topBottom, newWidth, newHeight) {
  const img = document.createElement('img');
  img.src = imagePath;

  const canvas = document.createElement('canvas');
    document.body.appendChild(canvas);
  const ctx = canvas.getContext('2d');

  img.addEventListener('load', function() {
  
  //Set your canvas size as your choice
  //here i just scaled by 10 with original dimension
    canvas.width = img.naturalWidth*10;
    canvas.height = img.naturalHeight*10;
    
    const cropLeft = leftRight[0];
    const cropRight = img.naturalWidth - leftRight[0] - leftRight[1];
    
    const cropTop = topBottom[0];
    const cropBottom = img.naturalHeight - topBottom[0] - topBottom[1];
    ctx.drawImage(
    img, 
    cropLeft,cropTop,
    cropRight, cropBottom,
    0,0, //here you can control placement of cropped image from left and top, by default it stays in 0,0 meaning the top left corner of the canvas
    newWidth,newHeight //new width and height of cropped image
    );
  });
}

//Size of this image is 100x100 px
const img = "https://dummyimage.com/100.png/09f/fff";

//here [10,10] meaning crop 10px from left and 10px from right
//here [20,20] meaning crop 20px from top and 20px from bottom
cropImage(img,[10,10],[20,20], 100, 100);