With the development of detecting technology, the display technology for the real-time waveform display of detected parameters is developing continuously.  For instance, a medical monitor is a kind of device that can display a variety of physiological parameters promptly and simultaneously.  Current medical monitors can display a variety of physiological parameters, such as IBP, NIBP, CO, CO2, SPO2, ECG and the like, while multi-lead ECG parameters require to display multichannel ECG parameters on one screen.  The medical monitor will draw waveform data of amplitude of each parameter changing with time, in order to reflect the changing information of these parameters. 
Since the parameters will change with time, the parameter data measured at adjacent points are normally different, sometimes significantly different, so that the waveform data displayed on the screen is not changed continuously.  Therefore, the difficult point of waveform date display is the problem of how to smoothen the waveform. 
Several methods for drawing waveform data on a screen is proposed in order to solve the problem of smoothening a waveform. 
The early method is a point-painting method that fills the gaps between incontinuous waveform data with vertical lines when drawing waveform data on screen, to overcome incontinuity of waveforms.  The point-painting method is relatively simple, but because vertical lines are used for filling, and when two waveform data points have different horizontal coordinates, the displaying will present much more incontinuous points, so that the smoothening effect of the waveform is very poor and can not satisfy vision demands when using the point-painting method. 
In order to overcome the drawbacks of the point-painting method, an interpolation fitting method is then proposed to draw waveform data.  Different from the point-painting method, the interpolation fitting method achieve the purpose of waveform smoothing by extending two adjacent waveform data points and interpolating the fitting data therein.  However, there are also drawbacks in the interpolation fitting method because this method needs to interpolate as many interpolation data as possible to achieve the purpose of smoothening a waveform, while it needs a large number of multiplication and division operations to produce a large number of interpolation data, and the length of the waveform displayed on one screen will be reduced and thus the information content displayed will be decreased due to a plurality of fitting data interpolated. 
Therefore, a color level drawing method is proposed to draw waveforms on a screen.  The color level drawing method, which is an improvement of the point-painting method, changes the vertical line in the point-painting method to a gradation line gradually changed from a light color to a dark color, so as to the incontinuous parameter data points seem smooth because vision effect.  The color level drawing method can better show smooth waveforms on a screen.  This drawing method also requires a large number of multiplication and division operations, although the multiplication and division operation number is smaller than the interpolation simulation method.  Moreover, using the color level drawing method, the amount of information transmitted between a CPU and a hardware processing module will be increased due to the subsection of the vertical lines, this proposes a higher requirement for the operation ability of the CPU and transmission bandwidth of the hardware when the number of waveform displayed on one screen increased.