https://dungeonchannel.com/wp-content/themes/oblivion201806/js/ima…?ver=f55f4fc9989d958c4e040335cb3a196d

1function ScaleImage(srcwidth, srcheight, targetwidth, targetheight, fLetterBox) {
2
3    var result = { width: 0, height: 0, fScaleToTargetWidth: true };
4
5    if ((srcwidth <= 0) || (srcheight <= 0) || (targetwidth <= 0) || (targetheight <= 0)) {
6        return result;
7    }
8
9    // scale to the target width
10    var scaleX1 = targetwidth;
11    var scaleY1 = (srcheight * targetwidth) / srcwidth;
12
13    // scale to the target height
14    var scaleX2 = (srcwidth * targetheight) / srcheight;
15    var scaleY2 = targetheight;
16
17    // now figure out which one we should use
18    var fScaleOnWidth = (scaleX2 > targetwidth);
19    if (fScaleOnWidth) {
20        fScaleOnWidth = fLetterBox;
21    }
22    else {
23       fScaleOnWidth = !fLetterBox;
24    }
25
26    if (fScaleOnWidth) {
27        result.width = Math.floor(scaleX1);
28        result.height = Math.floor(scaleY1);
29        result.fScaleToTargetWidth = true;
30    }
31    else {
32        result.width = Math.floor(scaleX2);
33        result.height = Math.floor(scaleY2);
34        result.fScaleToTargetWidth = false;
35    }
36    result.targetleft = Math.floor((targetwidth - result.width) / 2);
37    result.targettop = Math.floor((targetheight - result.height) / 2);
38
39    return result;
40}