public Integer getPadding() {
            if (padding == null) {
                return 1;
            }

            if (padding < 0) {
                return 0;
            }

            if (padding > 4) {
                return 4;
            }

            return padding;
        }
output qrcode image type, default png
plugins/qrcode-plugin/src/main/java/com/github/hui/quick/plugin/qrcode/wrapper/QrCodeGenWrapper.java