javascript - 将 Canvas 复制到另一个 Canvas

Question

我使用此功能将旧 Canvas 复制到新 Canvas

function cloneCanvas(oldCanvas) {

        //create a new canvas
        var newCanvas = document.createElement('canvas');
        var context = newCanvas.getContext('2d');

        //set dimensions
        newCanvas.width = oldCanvas.width;
        newCanvas.height = oldCanvas.height;

        //apply the old canvas to the new one
        context.drawImage(oldCanvas, 0, 0);

        //return the new canvas
        return newCanvas;
    }

我像这样使用这个函数

            var oldCanvas = $(this).parent().parent().find('td:first-child canvas')

            $("div.previewImg").append(cloneCanvas(oldCanvas))

但是我得到这个错误:(

Failed to execute 'drawImage' on 'CanvasRenderingContext2D': No function was found that matched the signature provided

请帮帮我，我该如何解决这个错误

谢谢

Answer 1

首先要确保你得到的是一个元素而不是一个数组，使用:

$(this).parent().parent().find('td:first-child canvas').first();

第二个:

要从数组中复制图像数据，请使用 toDataUrl() :

canvasDataImg = oldCanvasContext.toDataURL("image/png");

然后绘制到新的 Canvas 上。