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在调整电视图像的线性、幅度及中心位置时,通常要借助电视台播放的测试图或自备的电视信号发生器。然而,测试图并非随时可得,电视信号发生器也未必人人具备。在业余条件下,借助一台电脑(型号不限,但必须具备LOGO语言功能)是很容易绘制出测试大圆和棋盘方格的。 LOGO语言的海龟作图初步知识详见各型电脑使用说明书,笔者不再赘述。特别需要提醒注意的是,由于目前多数电视机屏幕纵横比约为3:4.故海龟纵向移动10步的实际路线长度与横向移动10步的实际路线长度之比约为3:4。如果事先在设置命令时未加校正,绘制的正方形将变成纵横比为3:4的长方形,圆形也变成纵、横轴长度比约为3:4的椭圆。因此,在编制程
When adjusting the linearity, amplitude and center of the television picture, it is often necessary to resort to a test chart or a self-contained television signal generator that is being played on the television station. However, test charts are not always available, and TV signal generators may not be available to everyone. Amateur conditions, with a computer (no model, but must have LOGO language features) is easy to draw the test circle and checkerboard checkered. LOGO language turtle mapping preliminary knowledge see various types of computer user manual, the author will not repeat them. It is important to note that due to the current aspect ratio of most television screens of around 3: 4, the ratio of the actual length of a sea turtle moving 10 steps in a vertical direction to the actual length of a 10-step moving path is about 3: 4. If you set the command without correction in advance, the drawn square will become a rectangle with an aspect ratio of 3: 4, and the circle will become an ellipse with a length to horizontal length of about 3: 4. Therefore, the preparation process