?window.onload?=?function()?{ ????????canvas.width?=?1152 ????????canvas.height?=?768 ????????image.src?=?'img-lg.jpg' ????????image.onload?=?function()?{ ????????????offCanvas.width?=?image.width ????????????offCanvas.height?=?image.height ????????????scale?=?offCanvas.width?/?canvas.width?//原圖大小是畫布的3陪 ????????????context.drawImage(image,?0,?0,?canvas.width,?canvas.height) ????????????offContext.drawImage(image,?0,?0) ????????} ????}canvas（注意不是offCanvas）中繪制的原圖大小是畫布的3陪，為什么可以將整張圖片繪制進(jìn)去，drawImage（）應(yīng)該不是自帶縮放的吧？求解答。