问题描述
我正在尝试降低画布上绘制的图像的不透明度，但它不起作用
var img = new Image();
const canvas = document.getElementById("myCanvas");
const ctx = canvas.getContext('2d');
img.src = './picture.jpg';
canvas.width = img.width;
canvas.height = img.height;
img.style.opacity = 0.5;
ctx.drawImage(img,30,canvas.width,canvas.height);
解决方法
/// only image will have alpha affected:
context.globalAlpha = 0.5;
context.drawImage(image,x,y);
context.globalAlpha = 1.0;