title: How to plot a function in Flutter with canvas in a cartesian chart
body: <p>I'm trying to plot a function in Flutter with canvas in a cartesian chart. Let's say that we want to draw a sine wave: y(x) = SIN(X). Now the problem is drawing a very smooth line curve. I tried to with this method: draw a lot of straight lines that follow the SINE trend.
  This works very well, and it is smooth. But if I try to increase stroke width, that happens: the line becomes transparent. And the more the number of straight lines drawed, the more is the transparency. I have a thory for that. I noticed that if you draw a simple straight line and set the stroke width to a low value, the line becomes transparent. Actually, a line width can't be lower than a one pixel. But if that line is set to a higher transparency it can appear little than a pixel. In my example, to compund a sine wave I needed to put together a lot of lines (1000-5000). So the width of each line is lower than a pixel and it becomes transparent. Is that right? How can it be solved? Thank you very much!</p>