js同比例缩放图片

function DrawImage(ImgD, FitWidth, FitHeight) {

    var image = new Image();

    image.src = ImgD.src;

    if (image.width > 0 && image.height > 0) {

        if (image.width / image.height >= FitWidth / FitHeight) {

            if (image.width > FitWidth) {

                ImgD.width = FitWidth;

                ImgD.height = (image.height * FitWidth) / image.width;

            } else {

                ImgD.width = image.width;

                ImgD.height = image.height;

            }

        } else {

            if (image.height > FitHeight) {

                ImgD.height = FitHeight;

                ImgD.width = (image.width * FitHeight) / image.height;

            } else {

                ImgD.width = image.width;

                ImgD.height = image.height;

            }

        }

    }

}