HTML5 canvas如何更改putImageData规模

Question

如何更改putImageData规模与规模(1.5,1.5)不工作..

var imageData = context.getImageData(0, 0, canvas.width, canvas.height);
context.clearRect(0, 0, canvas.width, canvas.height);
context.scale(1.5, 1.5);
context.putImageData(imageData, 0, 0);

Answer 1

更正,您的代码不会缩放现有图纸.

context.scale仅影响新图纸,而不影响现有图纸.

context.putImageData 将保存的原始像素放回画布上,但putImageData不是绘图命令,因此其结果不会缩放.

要缩放现有像素,您必须将像素保存到画布外的实体.外部实体可以是新的Image元素或第二个Canvas元素.

示例代码和演示:http: //jsfiddle.net/m1erickson/p5nEE/

// canvas related variables
var canvas=document.getElementById("canvas");
var context=canvas.getContext("2d");

// draw a test square
context.fillStyle="red";
context.fillRect(0,0,50,50);

// create an image from the canvas
// clear & scale the canvas
// draw the image to the canvas
var imageObject=new Image();
imageObject.onload=function(){

    context.clearRect(0,0,canvas.width,canvas.height);
    context.scale(1.2,1.2);
    context.drawImage(imageObject,0,0);

}
imageObject.src=canvas.toDataURL();