使用jquery canvasCrop裁剪图像返回图像顶部和底部的黑色背景

Question

我正在使用jquery上传图片画布。当我上传图像，调整大小然后保存时，裁剪的图像背景为黑色。我想将黑色背景更改为白色。

给出的是例子...... Result Image

   getDataURL: function(type){
                    var type = type||"png",
                        width = thumbBox.width,
                        height = thumbBox.height,
                        hiddenCanvas = document.createElement("canvas"),
                        hiddenContext = hiddenCanvas.getContext("2d");
                    hiddenCanvas.width = width;
                    hiddenCanvas.height = height;
                    hiddenCanvas.width = $(".thumbBox").width();
                    hiddenCanvas.height = $(".thumbBox").height();
    //                hiddenContext.drawImage(visbleCanvas, clipArgument.sx, clipArgument.sy, width, height, 0, 0, width, height);
                    hiddenContext.drawImage(visbleCanvas, clipArgument.dx, clipArgument.dy, visbleCanvas.width,visbleCanvas.height);
                    return hiddenCanvas.toDataURL('image/'+type);
                }

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