https://developers.weixin.qq.com/miniprogram/dev/api/canvas/CanvasContext.fillText.html

比如这样,在开发者工具上生效,手机上就全黑色了

// Create gradient
var gradient=ctx.createLinearGradient(0,0,c.width,0);
gradient.addColorStop("0","magenta");
gradient.addColorStop("0.5","blue");
gradient.addColorStop("1.0","red");
// Fill with gradient
ctx.fillStyle=gradient;
ctx.fillText("Big smile!",10,90);