【求教】各位大佬为什么我的canvas保存为图片后多了一部分透明填充？

      // 保存canvas为图片  
      uni.canvasToTempFilePath({  
        x: this.border.left,  
        y: this.border.top,  
        width: this.border.width,  
        heght: this.border.width,  
        destWidth: this.border.width * this.systemInfo.pixelRatio,  
        destHeight: this.border.width * this.systemInfo.pixelRatio,  
        quality: 1,  
        canvasId: "background",  
        success: ({ tempFilePath }) => {  
          console.log("tempFilePath: ", tempFilePath);  
          this.src = tempFilePath;  
        },  
      });