常用图像源:
图像元素:img
视频元素 video
canvas: canvas
drawImage()操作方式:
绘图+位移:drawImage(image,x,y)
绘图+位移+缩放:drawImage(image,x,y ,width , height)
绘图+裁切+位移+缩放:drawImage(image,x1,y 1,w1 , h1,x2 , y2 , w2 , h2)
drawImage()作用:
把现有图片绘制到canvas中去
便于以后通过canvas获取图片的像素集合
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