function getEdges(tempcanv, colour, which, condition) {
    let ledge = [], redge = [], tedge = [], bedge = [];
    const canvwidth = tempcanv.width, canvheight = tempcanv.height;
    const contextd = tempcanv.getContext('2d');
    for (let y = 0; y < canvheight; y++) {//left edge
        for (let x = 0; x < canvwidth; x++) {
            const data = contextd.getImageData(x, y, 1, 1).data;
            if (condition(data[which], colour)) {
                ledge.push(x);
                break;
            }
        }
    }
    ledge = Math.min(...ledge);
    const llim = ledge === 0 ? ledge : ledge - 1;
    for (let x = llim; x < canvwidth; x++) {//top edge
        for (let y = 0; y < canvheight; y++) {
            const data = contextd.getImageData(x, y, 1, 1).data;
            if (condition(data[which], colour)) {
                tedge.push(y);
                break;
            }
        }
    }
    tedge = Math.min(...tedge);
    const tlim = tedge === 0 ? tedge : tedge - 1;
    for (let y = tlim; y < canvheight; y++) {//right edge
        for (let x = canvwidth - 1; x >= ledge; x--) {
            const data = contextd.getImageData(x, y, 1, 1).data;
            if (condition(data[which], colour)) {
                redge.push(x);
                break;
            }
        }
    }
    redge = Math.max(...redge);
    for (let x = llim; x <= redge; x++) {//bottom edge
        for (let y = canvheight - 1; y >= tedge; y--) {
            const data = contextd.getImageData(x, y, 1, 1).data;
            if (condition(data[which], colour)) {
                bedge.push(y);
                break;
            }
        }
    }
    return [ledge, tedge, redge + 1, Math.max(...bedge) + 1]
}

//(canvas passed, colour threshold, R,G or B, greater or less than)
getEdges(canvas, 180, 0, (a, b) => a > b))

function getEdges(tempcanv, colour, which, condition) {
  let ledge = -1, redge = -1, tedge = -1, bedge = -1;
  const canvwidth = tempcanv.width, canvheight = tempcanv.height;
  const contextd = tempcanv.getContext('2d');
  const imageData = contextd.getImageData(0, 0, canvwidth, canvheight).data; //gets all image data
  for (let x = 0; x < canvwidth; x++) {//left edge
    if(ledge > 0 ) {
      break;
    }
    for (let y = 0; y < canvheight; y++) {
      //(x*canvwidth+y)*3 is for getting the current location
      if (condition(imageData[(y*canvwidth+x)*3+which], colour)) { //might need to switch x and y? I am not sure in which order getImageData is
        ledge = x;
        break;
      }
    }
  }