这个函数实现图片放大和缩小 只要改变变量：dst_cvsize.width 的值，就可以按比例缩放图像 注意：这里的测试图像大小为512*512-This function is achieved as long as the image to zoom in and change the variables: dst_cvsize.width value, you can scaling the image NOTE: This test image size is 512* 512