平移和旋转后 canvas 上的 getImageData

Question

I'm trying to extract a part of an image through the getImageData function for canvas.

The difficulty is that my part is rotated. My goal is to extract for example the rectangle on the image:

To draw the rectangle below, I use a translation and a rotation, but these functions don't work when we use getImageData.

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");

var img = new Image();
img.onload = function () {
    ctx.drawImage(img, 0, 0, img.width, img.height);
drawRect();
}
img.src = "https://dummyimage.com/300x150/5873f0/ffffff.jpg"; 


function drawRect(){
    ctx.save();
    ctx.translate(75, 100);
    ctx.rotate(20 * Math.PI / 180)
    // imgData = ctx.getImageData(-50, -25, 100, 50);
    ctx.strokeStyle = 'black';
    ctx.strokeRect(-50, -25, 100, 50);
    ctx.restore()
}

This is the Fiddle I use. Thanks!