The image must be clear in order to make it easy to cut out.  If you are drawing your own image, clearly outline the areas of the image that will be cut out for the stencil. Remember that you need to define the edges and the details of your image, or the stencil will not portray your original drawing. If you are using a photograph or an online image, you need to use a software program that can adjust the contrast and brightness of your image so that you have defined dark and light areas. It will probably be easiest to switch the image into purely black and white.  Make sure that your current design will work as a stencil. If you are attempting to create a complex image with textures or shadows, make sure that you design does not force you to cut whole sections out of the stencil. Alter the image so that the stencil will remain as a single piece.  Photo images also work best if you erase the backgrounds first. This may be the most time-consuming portion of the process. After the image has been printed, it may be a good idea to outline any areas areas in which the contrast remains ill-defined. You must have a clear image to cut out for the stencil.

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Write a summary of the previous text in Vietnamese:
Vẽ hình ảnh với những đường rõ nét và sự tương phản rõ rệt. In bức ảnh ưng ý của bạn ra giấy in thông thường (nếu cần).