You can make a perfect silhouette with any photo with a Vector Mask. It is quite easy to do. Making a silhouette with a Vector Mask has an advantage. If you resize it, no pixels are lost i.e. the image does not deteriorate if you increase or decrease its size.
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This is the image I will use for making a silhouette with a Vector Mask
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This is the silhouette made with a Vector Mask.