Disclosed is a method for determining optimum color gradation levels used by a color gradation barcode in a system including a rendering device for rendering the barcode and a detector for detecting the barcode. The method includes: (a) obtaining input color gradation data; (b) rendering, by using the rendering device, a test pattern based on the input color gradation data, the test pattern comprising at least one color gradation pattern; (c) detecting, by using the detector, the rendered test pattern to generate detected color gradation data; (d) based on the detected color gradation data and the input color gradation data, determining a plurality of optimum color gradation levels to be used for a color gradation barcode; and (e) storing the plurality of optimum color gradation levels.